WO2020240810A1 - Power conversion device - Google Patents

Power conversion device Download PDF

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Publication number
WO2020240810A1
WO2020240810A1 PCT/JP2019/021681 JP2019021681W WO2020240810A1 WO 2020240810 A1 WO2020240810 A1 WO 2020240810A1 JP 2019021681 W JP2019021681 W JP 2019021681W WO 2020240810 A1 WO2020240810 A1 WO 2020240810A1
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WO
WIPO (PCT)
Prior art keywords
power
voltage
capacitor
converter
load device
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Application number
PCT/JP2019/021681
Other languages
French (fr)
Japanese (ja)
Inventor
恭大 金子
崇裕 石黒
Original Assignee
東芝エネルギーシステムズ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by 東芝エネルギーシステムズ株式会社 filed Critical 東芝エネルギーシステムズ株式会社
Priority to PCT/JP2019/021681 priority Critical patent/WO2020240810A1/en
Priority to JP2021521720A priority patent/JP7031065B2/en
Publication of WO2020240810A1 publication Critical patent/WO2020240810A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/49—Combination of the output voltage waveforms of a plurality of converters

Definitions

  • An embodiment of the present invention relates to a power conversion device.
  • the problem to be solved by the present invention is to provide a power converter capable of more appropriately controlling the power converter according to the situation of the power transmission system.
  • the cell control unit controls the switching element based on the control signal output by the control unit to control the power output to the DC side, and transfers the voltage of the capacitor detected by the voltage detection unit to the control unit. provide. Converts AC power to DC power or DC power to AC power.
  • the load device is connected between the positive electrode wire and the negative electrode wire or the ground wire on the DC side of the converter. The control unit controls the load device so that the load device consumes or stores electric power based on the voltage of the capacitor included in the converter.
  • FIG. 1 is a diagram showing an example of the configuration of the DC power transmission system 1.
  • the DC power transmission system 1 is a multi-terminal DC power transmission system that exchanges power between a plurality of conversion stations.
  • Each of the AC electric facilities 2 (2-1 to 2-5 in the figure) scattered over a long distance in the DC power transmission system 1 is connected to the power conversion device 10.
  • the AC electric facility 2 is a power plant (for example, a wind power plant) or another AC system.
  • the power conversion device 10 is connected to a plurality of other power conversion devices 10 via a DC system 3 (3-1 to 3-8 in the figure).
  • the power conversion device 10 may be referred to as a conversion station.
  • AC equipment and conversion stations are scattered at five locations, and there are a total of eight sections (sections 3-1 to 3-8 in the figure) of DC transmission lines connecting the conversion stations. It is a multi-terminal DC power transmission system when The number of AC electrical equipment 2 and conversion stations, and the number of sections and lines of DC transmission lines are not limited to this.
  • the processing of the present embodiment is applied to a loop-shaped or non-loop-shaped DC power transmission system or a two-terminal DC power transmission system in which at least three or more conversion stations connected to the AC electrical equipment 2 are connected by two sections of the DC power transmission line. Etc. may be applied.
  • FIG. 2 is a diagram focusing on the functional configuration of the power conversion device 10.
  • a power converter 10 and a DC circuit breaker 210 (210-1, 210-2) are connected in parallel to the DC bus 200 (200P, 200N in the figure) via an electric line.
  • the power converter 10 includes, for example, a power converter 20, a load device 80, and a control device 100.
  • the power converter 20 and the load device 80 are connected in parallel via an electric wire.
  • the power converter 20 has a transformer TR and a plurality of legs 30 (30-1 to 30-3 in the figure).
  • a transformer TR is connected between the AC electrical equipment 2 and the terminal NAC of each leg 30.
  • the transformer TR includes a set of a primary winding and a secondary winding for three phases.
  • the three phases are, for example, an alternating current U phase, an alternating current V phase, and an alternating current W phase.
  • AC U-phase AC power, AC V-phase AC power, and AC W-phase AC power are supplied to the primary winding side of the transformer TR, respectively.
  • the transformer TR transforms the supplied AC power and outputs the transformed AC power to the secondary winding side (leg 30 side).
  • Each leg 30 includes a positive arm 40P (40P-1 to 40P-3) and a negative arm 40N (40N-1 to 40N-3).
  • a terminal NAC is connected between the positive arm 40P and the negative arm 40N.
  • the secondary winding U phase of the transformer TR is connected to the terminal NAC of the leg 30-1, and the secondary winding V phase of the transformer TR is connected to the terminal NAC of the leg 30-2.
  • the W phase of the secondary winding of the transformer TR is connected to the terminal NAC of the leg 30-3.
  • one or more cells 50 are connected in series.
  • “N” is an arbitrary natural number.
  • one or more cells 50 are connected in series.
  • N cells (N ⁇ 2) are connected in series to the positive arm 40P and the negative arm 40N, respectively.
  • the cell 50 functions as a unit converter, and the arm 40 outputs an arbitrary voltage such as a stepped AC voltage.
  • the above-mentioned stepped AC voltage output is performed by shifting the timing of the switching operation of the switching element (see FIG. 3) included in each cell 50.
  • the control device 100 controls the switching element based on the arm voltage command value X1 input to each cell 50 to control the switching operation.
  • Each cell 50 detects the voltage of the cell capacitor contained therein, and outputs the voltage detection value of the cell capacitor (capacitor voltage detection value X2) to the control device 100. Details of the cell 50 and the contents of the control will be described later.
  • the buffer reactor LB and the current sensor CT are connected in series with the positive arm 40P.
  • the buffer reactor LB and the current sensor CT are connected in series with the negative arm 40N.
  • the buffer reactor LB suppresses the short-circuit current flowing through the cell 50.
  • the current sensor CT detects the current flowing through each buffer reactor LB and outputs the arm current detection value X3 to the control device 100.
  • each of the positive side arm 40P and the negative side arm 40N the voltage of each cell 50 is added to determine the output voltage.
  • the output DC voltage of the positive arm 40P is a positive voltage with reference to the AC terminal NAC.
  • the positive DC voltage generated by the positive arm 40P is output to the terminal NDCP.
  • the output DC voltage of the negative arm 40N is a negative voltage with reference to the AC terminal NAC.
  • the negative DC voltage generated by the negative arm 40N is output to the terminal NDCN.
  • the power converter 20 supplies DC power between the terminal NDCP and the terminal NDCN.
  • the load device 80 is, for example, a resistor, a device having a power storage function, or the like.
  • the load device 80 has a function of adjusting the DC side electric power of the power converter 20 by consuming or storing the DC side electric power in the operating state.
  • the load device 80 is connected between the positive electrode wire and the negative electrode wire (or the ground wire) on the DC side of the power converter 20.
  • the load device 80 is connected to the terminal NDCP and the terminal NDCN, and is controlled to an operating state or a stopped state according to the input load device operation command X4.
  • the cell capacitor which is an energy storage element of each cell 50, may be overcharged and the cell capacitor may become overvoltage. is there.
  • the load device 80 when the load device 80 is put into the operating state, the electric power on the DC side is adjusted. By this adjustment, the balance between the power on the AC side and the power on the DC side is maintained, and the overvoltage of the cell capacitor is avoided.
  • the load device 80 outputs a load device state signal X5 indicating an operating state or a stopped state according to the operating state.
  • the DC bus 200P is connected to the terminal NDCP, and the DC bus 200N is connected to the terminal NDCN.
  • a DC circuit breaker 210 is connected to at least one of the contacts between the DC bus 200 and the DC system 3 (DC transmission line) connected to the DC bus 200.
  • the control device 100 can control the open / closed state of the DC circuit breaker 210.
  • the DC circuit breaker 210 may be one DC circuit breaker or may include a plurality of DC circuit breakers.
  • the DC circuit breaker 210-1 is connected between the DC bus 200P and the DC system 3.
  • the DC circuit breaker 210-2 is connected between the DC bus 200N and the DC system 3.
  • the DC circuit breaker 210 is connected to a predetermined conversion station (first conversion station, second conversion station, etc.) via the DC system 3.
  • the DC circuit breaker 210 outputs the DC circuit breaker status signal X7 indicating that the open operation or the closed operation is performed and the open operation or the closed operation is performed in response to the DC circuit breaker operation command X6 output by the control device 100 to the control device 100. To do.
  • the DC circuit breaker 210-2 connected to the negative side DC bus 200N or the negative side DC bus 200N may be omitted.
  • the control device 100 is realized by a processor such as a CPU (Central Processing Unit) executing a program (software) stored in the storage device.
  • the control device 100 is realized by hardware (including a circuit unit: circuitry) such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and GPU (Graphics Processing Unit). It may be realized by the cooperation of software and hardware.
  • the program may be stored in advance in a storage device such as an HDD (Hard Disk Drive) or a flash memory, or is stored in a removable storage medium such as a DVD or CD-ROM, and the storage medium is stored in the drive device. It may be installed by being attached.
  • the control device 100 acquires the capacitor voltage detection value X2 and the arm current detection value X3 from the power converter 20, and based on these detected values, performs a predetermined calculation to perform various operation amounts (arm voltage command value X1). ) Is derived.
  • the arm voltage command value X1 obtained as described above is transmitted to each cell 50.
  • the control device 100 controls the load device 80 so that the load device 80 consumes or stores electric power based on the voltage of the capacitor of the cell 50.
  • the control device 100 performs an operation for determining the operation or stop of the load device 80, derives the load device operation command X4 based on the calculation result, and transmits the derived load device operation command X4 to the load device 80 ( Details will be described later).
  • the control device 100 acquires the load device status signal X5 indicating the operating state of the load device 80 from the load device 80. Based on the acquired load device status signal X5, the control device 100 performs an operation for determining the opening / closing operation of the DC circuit breaker 210 to derive the DC circuit breaker operation command X6. The control device 100 transmits the derived DC circuit breaker operation command X6 to the DC circuit breaker 210. The control device 100 acquires the DC circuit breaker status signal X7 indicating the operating state of the DC circuit breaker 210, and based on the acquired DC circuit breaker status signal X7, performs an operation for determining the opening / closing operation of the DC circuit breaker 210. (Details will be described later).
  • FIG. 3 is a diagram showing an example of the functional configuration of the cell 50.
  • the cell 50 is, for example, a half-bridge type chopper cell.
  • the cell 50 includes a terminal 50A, a terminal 50B, a switching element 52A, a switching element 52B, a cell capacitor 54, a feeding circuit 56, a cell control unit 58, a feedback diode 60A, and a feedback diode 60B. It is equipped with a voltage sensor VT.
  • Terminal 50A is connected to terminal NDCP or other cell 50, and terminal 50B is connected to other cell 50 or terminal NAC.
  • the switching element 52A and the switching element 52B are self-extinguishing semiconductor elements such as an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (metal-oxide-semiconductor field-effect transistor). Two of these switching elements 52A and 52B are connected in series, for example.
  • the feedback diode 60A and the feedback diode 60B are connected in series, and are connected to the switching element 52A and the switching element 52B in antiparallel, respectively.
  • the electric wire extending from the terminal 50A is connected between the switching element 52A and the switching element 52B connected in series, and between the feedback diode 60A and the feedback diode 60B connected in series.
  • the cell capacitor 54 is connected in parallel to two switching elements 52A and 52B connected in series.
  • the power supply circuit 56 is directly connected to the cell capacitor 54.
  • the power supply circuit 56 is a step-down circuit.
  • the power supply circuit 56 supplies electric power to the cell control unit 58 by outputting the voltage output by the cell capacitor 54 to the cell control unit 58.
  • the voltage sensor VT detects the potential difference between both ends of the cell capacitor 54 and outputs the detected value to the cell control unit 58.
  • the first side (positive terminal side) of the switching element 52A and the feedback diode 60A is connected to the first side (positive terminal side) of the voltage sensation VT.
  • the second side (negative terminal side) of the switching element 52B and the feedback diode 60B is connected to the second side (negative terminal side) of the voltage sensation VT via an electric wire extending from the terminal 50B.
  • the cell control unit 58 controls the switching element 52 based on the control signal output by the control device 100 to control the power output to the DC bus 200, and provides the voltage detected by the voltage sensor VT to the control device 100. To do.
  • the cell control unit 58 acquires the detection value detected by the voltage sensor VT and the arm voltage command value X1 output to the control device 100, and based on the acquired information, various calculations (for example, a calculation for PWM control). )I do.
  • the control device 100 generates a gate signal G1 and a gate signal G2 according to the calculation result for PWM control, outputs the generated gate signal G1 to the gate of the switching element 52A, and outputs the generated gate signal G2 to the switching element. Output to the gate of 52B.
  • the control signal output by the control device 100 may include a converter stop command ES for stopping the power conversion operation of the cell 50.
  • the cell control unit 58 acquires the converter stop command ES, the cell control unit 58 stops the power conversion operation of each cell 50.
  • the cell control unit 58 transmits the capacitor voltage detection value X2 to the control device 100.
  • the cell 50 outputs the voltage of the cell capacitor 54 when the switching element 52A is on-controlled and the switching element 52B is turned off.
  • the cell 50 outputs a zero voltage when the switching element 52A is off-controlled and the switching element 52B is turned on.
  • a full bridge circuit as shown in FIG. 4 may be used instead of the half bridge circuit shown in FIG.
  • the full bridge circuit includes four switching elements 52C, 52D, 52E, 52F.
  • the switching element 52C and the switching element 52D are connected in series, and the switching element 52E and the switching element 52F are connected in series.
  • the series circuit of the switching element 52C and the switching element 52D and the series circuit of the switching element 52E and the switching element 52F are connected in parallel.
  • the feedback diodes 60C and 60D connected in series to the switching element 52C and the switching element 52D are connected in antiparallel.
  • the feedback diodes 60E and 60F connected in series to the switching element 52E and the switching element 52F are connected in antiparallel.
  • the power line extending from the terminal 50A is connected between the switching element 52C and the switching element 52D, and the power line extending from the terminal 50B is connected between the switching element 52E and the switching element 52F.
  • the switching elements 52C, 52E, 52D, and 52F are controlled based on the gate signal generated by the cell control unit 58.
  • FIG. 5 is a diagram for explaining an outline of the process executed by the control device 100.
  • the control device 100 performs, for example, [Process 1] to [Process 4].
  • [Process 1] is a process in which the control device 100 controls the load device 80 based on the voltage (capacitor voltage) of the cell capacitor 54 of the cell 50 to consume or store DC power. As a result, the overvoltage of the cell capacitor 54 is suppressed.
  • [Process 2] is a process in which the control device 100 suppresses the DC power calculation amount used for the control calculation when the DC accident is detected. This improves the controllability of the capacitor voltage. That is, the capacitor voltage is controlled within an appropriate range.
  • Process 3 is a process in which the control device 100 detects a DC accident based on the DC current value. As a result, a DC accident is detected quickly.
  • Process 4 is a process in which the control device 100 restarts the power converter 20 based on the state of the circuit breaker and the direct current. As a result, the power converter 20 is quickly restarted.
  • FIG. 6 is a diagram for explaining a process of determining a command value indicating the operation and stop of the load device 80.
  • the control device 100 includes an operation calculation unit A1.
  • the operation calculation unit A1 includes a start determination unit A2-1, a stop determination unit A2-2, and an SR-FF unit A2-3.
  • the operation calculation unit A1 performs each process based on the capacitor voltage. In the following description, it is assumed that the processing is performed using the average value of the capacitor voltages.
  • the average value of the capacitor voltage may be, for example, the total average value of the capacitor voltages detected in the plurality of cells shown in FIG. 2, or the capacitor voltage detection value included in the predetermined arm 40 (for example, 40-1). It may be the average value of X2.
  • the start determination unit A2-1 acquires the average value of the capacitor voltage and derives the time change rate of the acquired average value of the capacitor voltage (step B1). For example, the start determination unit A2-1 derives the difference from the previous sample value for each sample of the average value of the capacitor voltage, and performs filter calculation processing for high frequency noise removal on the derived result to determine the time change rate.
  • the time change rate is derived by deriving or performing moving average processing.
  • the start determination unit A2-1 compares the obtained time change rate with the preset threshold value ⁇ Vc, and is high when the time change rate of the average value of the capacitor voltage is larger than ⁇ Vc, and low when it is smaller. Is output (step B2). Next, the start determination unit A2-1 determines whether or not the average value of the capacitor voltages exceeds the threshold value Vth (first threshold value) (step B3).
  • the threshold value Vth is a value set to be equal to or higher than the rated value.
  • the threshold value Vth is 1 pu
  • high is output when the average value of the capacitor voltage is higher than 1 pu
  • high is output when the average value is higher than the value obtained by subtracting (or adding) a predetermined value to 1 pu
  • low is output when the value is lower.
  • the time change rate of the voltage exceeding the threshold value ⁇ Vc is the rate of change of the voltage according to the situation where the abnormal voltage rise occurs.
  • the voltage exceeding the threshold value Vth is a voltage according to the situation where an overvoltage is occurring.
  • the start determination unit A2-1 derives the logical product of the output signal of the process B2 and the output signal of the process B3 (step B4). If the output signal of process B2 and the output signal of process B3 are high, high is output in the process of step B4, and if the output signal of process B2 or the output signal of process B3 is low, the process of step B4 is low. Is output.
  • the start determination unit A2-1 outputs a continuous time in which the signal output in step B4 is continuously in a high state, and resets the output to zero when the signal output in the process of step B4 becomes low. (Step B5).
  • the start determination unit A2-1 compares the magnitude of the continuous time output in the process B5 with the preset predetermined time T1 (step B6).
  • the start determination unit A2-1 outputs high when the continuous time output in process B5 is longer than the specified time T1, and outputs low when it is shorter.
  • the start determination unit A2-1 sets high when the average value of the capacitor voltage continuously exceeds the threshold value Vth due to a DC accident or the like and rapidly increases, and low in other cases. Output.
  • the stop determination unit A2-2 compares the magnitude of the average value of the capacitor voltage and the preset threshold value Vch (step B7).
  • the stop determination unit A2-2 outputs high when the average value of the capacitor voltage is smaller than the threshold value Vch, and outputs low when the average value of the capacitor voltage is larger than the threshold value Vch.
  • the threshold value Vch (second threshold value) is a voltage below the rated level at which the capacitor voltage corresponds to the threshold value Vth or is smaller than the threshold value Vth.
  • the SR-FF unit A2-3 uses the output signal of the start determination unit A2-1 and the output signal of the stop determination unit A2-2 to generate the load device operation command X4 (step B8).
  • the SR-FF unit A2-3 inputs the output signal of the start determination unit A2-1 to the set terminal (S) of the SR-FF unit A2-3, and inputs the output signal of the stop determination unit A2-2 to the SR-FF unit. Input to the reset terminal (R) of A2-3.
  • the load device operation command X4 becomes high when the average value of the capacitor voltage exceeds the threshold value Vth and suddenly increases during the specified time T1 due to a DC accident or the like, and the average value of the capacitor voltage becomes equal to or less than the threshold value Vch. In some cases, it becomes a low signal.
  • the load device 80 operates or stops in accordance with the load device operation command X4 generated by the above process.
  • the load device 80 operates when the load device operation command X4 is a command indicating high, and stops when the load device operation command X4 is a command indicating low.
  • By operating the load device 80 an increase in the capacitor voltage is suppressed, and the power converter 20 is prevented from stopping due to an overvoltage.
  • FIG. 7 is a diagram showing an example of the relationship between the operation of the operation calculation unit A1 and the average value of the capacitor voltage and the voltage change rate.
  • the threshold value Vch is 1 pu.
  • the high signal is output in steps B2 and B3 between the time t + 2 and the time t + 3, the high signal is output in the process of step B4.
  • the high signal is output in the process of step B6, a signal for operating the load device 80 is generated, and the generated signal is the load device. It is output to 80.
  • step B7 a signal for stopping the operation of the load device 80 is generated, and the generated signal is output to the load device 80.
  • control device 100 controls the load device 80 so as to consume or store electric power in the load device 80 based on the voltage of the capacitor included in the power converter 20, thereby causing the overvoltage of the cell capacitor 54. Is suppressed. As a result, the control device 100 can more appropriately control the power converter 20 according to the situation of the DC power transmission system 1.
  • FIG. 8 is a diagram for explaining a process related to the calculation of the manipulated variable performed at the time of a DC accident.
  • a control calculation is performed inside the control device 100, and an operation amount for controlling the cell 50 is derived.
  • the control device 100 derives a DC power amount based on the capacitor voltage (DC voltage) and the amount of DC current flowing on the DC side of the self-converting station.
  • the control device 100 uses this DC power amount as a feedforward amount to perform various control calculations.
  • the DC power amount is derived based on the DC current of the process 3 described later.
  • the control device 100 includes a DC power calculation unit 110, a capacitor voltage control unit 112, an effective current command value calculation unit 114, an AC current control unit 116, a limiter 118, and a switching unit 120.
  • the capacitor voltage control unit 112 outputs the output Pc_ref related to the capacitor voltage control to the adder (step B10), and the DC power calculation unit 110 uses the DC power amount Pdc_ff, which is the feed forward amount, as the adder.
  • Output step B11
  • the adder adds the output Pc_ref output by the capacitor voltage control unit 112 and the DC power amount Pdc_ff output by the DC power calculation unit 110 (step B12).
  • the addition result is input to the effective current command value calculation unit 114.
  • the effective current command value calculation unit B12 outputs the output Id_ref to the AC current control unit 116 (step B15).
  • the AC current control unit 116 uses the output Id_ref output in the process of step B15 as the control command value of the effective current (step B16).
  • the limiter 118 processes the output of the DC power calculation unit 110 by processing the switching unit 120 in response to the DC accident detection signal X8 (steps B13 and B14).
  • the DC accident detection signal X8 is high when an accident has occurred on the DC side and low when the DC side is sound.
  • the DC accident detection signal X8 is given by the control device 100 of FIG. 2 described above, or is generated based on the DC current value by a method described later.
  • the upper limit value and the lower limit value used by the limiter 118 are, for example, values according to the rated capacity of the converter. Alternatively, use zero for both. As a result, the DC power amount Pdc_ff at the time of a DC accident is limited or invalidated, so that deterioration of the controllability of the capacitor voltage is suppressed.
  • a control signal for controlling the power converter 20 is generated based on the calculated amount of the DC side power.
  • a control signal is generated based on a value that limits the calculated amount of DC side power, so that the situation of the DC transmission system 1 is reached.
  • the power converter 20 can be controlled more appropriately.
  • FIG. 9 is a block diagram relating to the processing of the state detection unit A11 for detecting the accident state and the sound state of the DC system 3.
  • the current rapid increase detection unit A12 of the state detection unit A11 performs arithmetic processing based on the input DC current value Idc.
  • the state determination unit A13 of the state detection unit A11 performs arithmetic processing based on the output of the current rapid increase detection unit A12.
  • the SR-FF unit of the state detection unit A11 indicates whether the DC system 3 is in a sound state or an accident state based on the calculation result of the current rapid increase detection unit A12 and the calculation result of the state determination unit A13.
  • the DC accident detection signal X8 is output.
  • the direct current is the current flowing on the direct current side of the conversion station.
  • the control device 100 calculates the DC current value Idc by the following method, for example. (1)
  • the control device 100 obtains half the total amount of arm currents output from each arm as in the following equation (1). (Iarmpu + iarmnu + iarmpv + iarmnv + iarmpw + iarmnw) / 2 ⁇ ⁇ ⁇ Equation (1)
  • the arm currents iarmpu, iarmnu, iarmpv, iarmnv, iarmpw, and iarmnw are the positive arm 40P-1, the negative arm 40N-1, the positive arm 40P-2, the negative arm 40N-2, and the positive arm, respectively. This is the current output from 40P-3 and the negative arm 40N-3.
  • the arm current may be detected by a current sensor (not shown), or the control device 100 may be derived based on the calculation result regarding the control of the cell 50.
  • the control device 100 obtains the total sum iarmpu + iarmpv + iarmpw of each phase of the positive arm 40P. (3) The control device 100 obtains the total sum iarmnu + iarmnv + iarmnw of each phase of the negative arm 40N. (4) The control device 100 detects the current flowing through the DC circuit breaker 210 and obtains the sum of the currents of the lines sharing the contact. (5) When the control device 100 has a capacitor as an energy buffer on the DC side of the power converter 20 and detects the voltage on the DC side as in the two-level converter described later, the active power on the AC side is used. The DC current is obtained by dividing by the DC voltage. The active power on the AC side may be derived based on, for example, the detection result of the current sensor CT, the detection result of the current sensor VT, or the like.
  • the current rapid increase detection unit A12 calculates the absolute value of the DC current value Idc (step B20).
  • the current rapid increase detection unit A12 calculates the time change rate of the absolute value of the DC current value Idc output in step B16 (step B21).
  • a method of obtaining the time change rate there are a method of calculating the difference from the previous sample value for each sample and performing filter calculation processing for high frequency noise removal on the result, and a method of performing moving average processing and the like. ..
  • the current rapid increase detection unit A12 compares the magnitude of the time change rate output in step B21 with the preset threshold value ⁇ Idc (step B22). If the time change rate output in step B21 is larger than the threshold value ⁇ Idc, high is output, and if it is smaller than the threshold value ⁇ Idc, low is output.
  • the threshold value ⁇ Idc is set to a value larger than the time change rate of the direct current set during normal operation.
  • the threshold value ⁇ Idc is, for example, 0.1 pu / ms.
  • the DC current value Idc may be directly used for detecting the accident state. For example, by comparing the DC current value with the threshold value, it is detected that an accident state is caused by an abnormal increase in the DC current.
  • the threshold value is set to a value higher than the rated operation level. However, by using the time change rate, the accident state can be detected earlier.
  • the state determination unit A13 performs a negative operation on the signal output by the power rapid increase detection unit A12 (step B23).
  • the state determination unit A13 calculates the time during which the negatively calculated signal in step B23 is continuously in the high state (step B24).
  • the state determination unit A13 resets the output to zero when the signal output by the power rapid increase detection unit A12 becomes low.
  • the state determination unit A13 compares the magnitude of the processing result in step B24 with the preset predetermined time T2 (step B25). High is output when the time related to the processing result in step B25 is longer than the specified time T2, and low is output when the time is shorter than the specified time T2.
  • the SR-FF unit generates a DC accident detection signal X8 using the signal output by the current rapid increase detection unit A12 and the signal output by the state determination unit A13 (step B26).
  • the signal output by the current rapid increase detection unit A12 is input to the set terminal (S) of the SR-FF unit, and the signal output by the state determination unit A13 is input to the reset terminal (R) of the SR-FF.
  • the DC accident detection signal X8 is high when the DC side current suddenly increases due to a DC accident or the like and the time change rate of the DC current exceeds the threshold value ⁇ Idc, and the time change rate of the DC current during the specified time T2. Is low when the value is equal to or less than the threshold value ⁇ Idc.
  • the control device 100 detects that the DC side is in an accident state, and when the current change rate on the DC side becomes equal to or less than the specified value. By detecting that the DC side is no longer in the accident state, the accident state can be detected more quickly. Then, the control device 100 can quickly control the power converter 20 based on the detection result of the accident state. For example, as described in Process 2, when an accident state is detected, the control device 100 limits the calculated amount of DC power and generates a control signal for controlling the cell 50. As a result, the control device 100 can quickly and more reliably control the capacitor voltage to an appropriate state. Further, the control device 100 can quickly release the limitation on the amount of DC power when the accident state is no longer detected.
  • FIG. 10 is a block diagram relating to a process for determining whether or not the power converter 20 restarts the switching operation after the accident is eliminated.
  • Can the restart determination unit A20 of the control device 100 restart the switching operation of the power converter 20 in the gate block by using the open / closed state signal of the DC circuit breaker 210 of the own conversion station and the DC current? Judge whether or not.
  • the processing of the restart determination unit A20 will be described.
  • the power transmission availability determination unit A21 When at least one effective power transmission path is formed between the DC side of the self-conversion station and the DC system 3, the power transmission availability determination unit A21 outputs a high signal.
  • the power transmission availability determination unit A21 of the restart determination unit A20 inputs the DC circuit breaker status signal X7 of one or both of the DC circuit breaker 210-1 and the DC circuit breaker 210-2 of the own conversion station to the OR (OR). Step B30).
  • the DC circuit breaker state signal high indicates an open pole state and low indicates a closed pole state.
  • the power transmission availability determination unit A21 performs a negative operation on the signal output in the process of step B30 (step B31).
  • a high signal is output when any of the DC circuit breakers 210 is in the closed state and the DC bus 200 and the DC system 3 are electrically connected.
  • a low signal is output when all of the DC circuit breakers 210 are in the open state and the DC bus 200 and the DC system 3 are electrically disconnected.
  • the zero current determination unit A22 of the restart determination unit A20 detects that the DC current is substantially zero based on the DC current value Idc. First, the zero current determination unit A22 calculates the absolute value of the DC current value Idc (step B32). Next, the zero current determination unit A22 compares the magnitude of the processing result of step B32 with the near zero IZ (step B33). High is output when the DC current is smaller than Near Zero IZ, and low is output when the DC current is larger.
  • the near zero IZ is a signal for determining that no direct current is flowing, and is a signal showing a value close to zero such as 0.01pu.
  • the zero current determination unit A22 calculates the time during which the output signal output in step B33 is continuously in the high state (step B34). When the output signal of step B33 becomes low, the output of step B34 is reset to zero.
  • the zero current determination unit A22 compares the magnitude of the processing result in step B34 with the preset predetermined time T3 (step B35). If the processing result of step B35 is longer than the specified time T3, high is output, and if it is shorter, low is output.
  • the specified time T3 is a time of about 1 ms.
  • the restart determination unit A20 calculates the logical product of the signal output by the power transmission availability determination unit A21 and the signal output by the zero current determination unit A22 (step B36). Next, the restart determination unit A20 performs positive edge detection processing on the processing result of step B36 and outputs a restart signal (step B37). That is, the restart determination unit A20 outputs a pulsed restart signal only at the moment when the output signal output in step B36 changes from low to high.
  • the restart signal is a standby signal that keeps the power converter 20 in the stopped state when the signal output in step B36 is low, and the power converter 20 performs a switching operation when the signal output in step B36 is high. It is a signal that means restarting to restart. As a result, when the self-converter and the DC system 3 are connected so as to form at least one effective transmission path, and the current flowing on the DC side is approximately zero, the power converter 20 A restart permission signal X9 for restarting the switching operation is output.
  • the control device 100 can quickly restart the power converter 20 even when the power converter 20 is stopped due to a DC accident or the like.
  • any of the DC breakers 210 is a DC breaker.
  • the power converter 20 can be quickly restarted by releasing the gate block so that the power converter 20 resumes operation.
  • control device 100 can control the power converter 20 more appropriately by performing various processes according to the situation of the power transmission system. More specifically, it is possible to provide a power conversion device having improved operation continuation performance when the power transmission system is in an unsteady state.
  • FIG. 11 is a diagram showing an example of the configuration of the power conversion device 10 of the second embodiment.
  • the power converter 20 has at least one switching element (41P-1 to 40P-3A) for each of the positive arm 40P (40P-1A to 40P-3A) and each negative arm 40N (40N-1A to 40P-3A).
  • 41P-3, 41N-1 to 41N-3) are connected in series.
  • Feedback diodes 42 (42P-1 to 42P-3, 42N-1 to 42N-3) are connected in antiparallel to each of the switching elements.
  • the terminal NAC is located at the contact point between the positive arm 40P and the negative arm 40N.
  • An AC impedance LAC is interposed between the secondary winding of the transformer TR and the terminal NAC, and the current sensor CT is installed so as to detect the current flowing through the AC impedance LAC.
  • the AC impedance LAC may be formed by a reactor or a leakage impedance component of a transformer TR.
  • the energy storage element of the power converter 20 is a DC capacitor CDC connected between the terminal NDCP and the terminal NDCN.
  • the DC capacitor CDC has at least one or more series connection configurations. When a plurality of DC capacitors are connected in series, the neutral point is the terminal NDCM.
  • the voltage sensor 46P is provided so as to detect the voltage of the terminal NDCP and the terminal NDCM
  • the voltage sensor 46N is provided so as to detect the voltage of the terminal NDCM and the terminal NDCN.
  • one voltage sensor 46 is installed between the terminal NDCP and the terminal NDCN.
  • the process described in the first embodiment may be applied to the two-level inverter circuit as described above.
  • the control device 100 controls the load device 80 so that the load device 80 consumes or stores electric power based on the voltage of the capacitor included in the power converter 20.
  • the control device 100 controls the load device 80 to consume or store power when the difference between the active power on the AC side and the power on the DC side of the power converter 20 deviates from the specified range. You may. As a result, overvoltage is suppressed.

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Abstract

The power conversion device according to an embodiment has a converter, a load device, and a control unit. The converter includes at least three legs. Each of the legs includes an arm including one or more cells, an inductance connected to the AC side of the arm, and a current detection unit for detecting the current flowing through the inductance. The cells have a switching element, a capacitor, a voltage detection unit, and a control unit. The cell control unit controls the switching element on the basis of a control signal outputted by the control unit, controls the power outputted to a DC side, and provides the voltage of the capacitor detected by the voltage detection unit to the control unit. AC power is converted into DC power, or DC power is converted to AC power. The load device is connected between a positive wire and a negative wire or ground wire on the DC side of the converter. The control unit controls the load device, on the basis of the voltage of the capacitor included in the converter, so as to cause the load device to consume or store electrical power.

Description

電力変換装置Power converter
　本発明の実施形態は、電力変換装置に関する。 An embodiment of the present invention relates to a power conversion device.
　近年、複数の変換所間で電力融通を行う多端子直流送電システムが利用されている。直流送電システムにおいて、事故が発生した場合、電力を変換する電力変換器の運転が停止する場合がある。電力変換器が停止した場合には、再起動するまでに長時間を要してしまうことがある。 In recent years, a multi-terminal DC power transmission system that exchanges power between multiple conversion stations has been used. In the case of an accident in a DC power transmission system, the operation of the power converter that converts electric power may stop. If the power converter is stopped, it may take a long time to restart it.
特開２０１８－１４８３７号公報JP-A-2018-14837
　萩原　誠・赤城　泰文「モジュラー・マルチレベル変換器（ＭＭＣ）のＰＷＭ制御法と動作検証」、電気学会論文Ｄ（産業応用部門）、１２８巻７号、ｐｐ．９５７－９６５、２００８年 Makoto Hagiwara, Yasufumi Akagi, "PWM Control Method and Operation Verification of Modular Multi-Level Converter (MMC)", IEEJ Paper D (Industrial Application Division), Vol. 128, No. 7, pp. 957-965, 2008
　本発明が解決しようとする課題は、送電システムの状況に応じて、電力変換器をより適切に制御することができる電力変換装置を提供することである。 The problem to be solved by the present invention is to provide a power converter capable of more appropriately controlling the power converter according to the situation of the power transmission system.
　実施形態の電力変換装置は、変換器と、負荷装置と、制御部とを持つ。変換器は、少なくとも３つのレグを含む。前記レグのそれぞれは、一以上のセルを含むアームと、前記アームの交流側に接続されたインダクタンスと、前記インダクタンスに流れる電流を検出する電流検出部と、を含む。前記３つのレグのうち、第１レグはＵ相、第２レグはＶ相、第３レグはＷ相に接続される。前記セルは、スイッチング素子と、コンデンサと、電圧検出部と、制御部とを持つ。電圧検出部は、前記コンデンサの両端の電圧を検出する。セル制御部は、制御部により出力された制御信号に基づいて前記スイッチング素子を制御して直流側に出力する電力を制御し、前記電圧検出部により検出された前記コンデンサの電圧を前記制御部に提供する。交流電力を直流電力または直流電力を交流電力に変換する。負荷装置は、前記変換器の直流側における正極線と負極線または接地線との間に接続される。前記制御部は、前記変換器に含まれるコンデンサの電圧に基づいて、前記負荷装置に電力を消費または蓄電させるように前記負荷装置を制御する。 The power converter of the embodiment has a converter, a load device, and a control unit. The transducer includes at least three legs. Each of the legs includes an arm including one or more cells, an inductance connected to the AC side of the arm, and a current detection unit that detects a current flowing through the inductance. Of the three legs, the first leg is connected to the U phase, the second leg is connected to the V phase, and the third leg is connected to the W phase. The cell has a switching element, a capacitor, a voltage detection unit, and a control unit. The voltage detection unit detects the voltage across the capacitor. The cell control unit controls the switching element based on the control signal output by the control unit to control the power output to the DC side, and transfers the voltage of the capacitor detected by the voltage detection unit to the control unit. provide. Converts AC power to DC power or DC power to AC power. The load device is connected between the positive electrode wire and the negative electrode wire or the ground wire on the DC side of the converter. The control unit controls the load device so that the load device consumes or stores electric power based on the voltage of the capacitor included in the converter.
直流送電システムの構成の一例を示す図である。It is a figure which shows an example of the structure of a DC power transmission system. 電力変換装置の機能構成を中心に示す図である。It is a figure which mainly shows the functional structure of a power conversion apparatus. セルの機能構成の一例を示す図である。It is a figure which shows an example of the functional structure of a cell. ブリッジ回路の構成の一例を示す図である。It is a figure which shows an example of the structure of a bridge circuit. 制御装置が実行する処理の概要を説明するための図である。It is a figure for demonstrating the outline of the process executed by a control device. 負荷装置の動作および停止を示す指令値を決定する処理を説明するための図である。It is a figure for demonstrating the process of determining the command value which shows the operation and stop of a load device. 動作演算部の動作とコンデンサ電圧の平均値と電圧変化率との関係の一例を示す図である。It is a figure which shows an example of the relationship between the operation of the operation calculation part, the average value of a capacitor voltage, and the voltage change rate. 直流事故時に行われる操作量の演算に関する処理を説明するための図である。It is a figure for demonstrating the process concerning the calculation of the manipulated variable performed at the time of a DC accident. 直流系統の事故状態と健全状態を検知するための状態検出部の処理に関するブロック図である。It is a block diagram concerning the processing of the state detection part for detecting the accident state and the sound state of a DC system. 事故除去後に電力変換器がスイッチング動作を再開するか否かが決定される処理に関するブロック図である。It is a block diagram concerning the process which determines whether or not the power converter restarts a switching operation after an accident is eliminated. 第２実施形態の電力変換装置の構成の一例を示す図である。It is a figure which shows an example of the structure of the power conversion apparatus of 2nd Embodiment.
　以下、実施形態の電力変換装置を、図面を参照して説明する。 Hereinafter, the power conversion device of the embodiment will be described with reference to the drawings.
　（第１の実施形態）
　図１は、直流送電システム１の構成の一例を示す図である。直流送電システム１は、複数の変換所間で電力融通を行う多端子直流送電システムである。直流送電システム１における長距離範囲に点在する交流電気設備２（図中、２－１～２－５）のそれぞれは、電力変換装置１０と連系する。交流電気設備２は、発電所（例えば、風力発電所）や、その他の交流系統である。電力変換装置１０は、直流系統３（図中、３－１～３－８）を介して他の複数の電力変換装置１０と接続されている。以下、電力変換装置１０を、変換所と称する場合がある。 (First Embodiment)
FIG. 1 is a diagram showing an example of the configuration of the DC power transmission system 1. The DC power transmission system 1 is a multi-terminal DC power transmission system that exchanges power between a plurality of conversion stations. Each of the AC electric facilities 2 (2-1 to 2-5 in the figure) scattered over a long distance in the DC power transmission system 1 is connected to the power conversion device 10. The AC electric facility 2 is a power plant (for example, a wind power plant) or another AC system. The power conversion device 10 is connected to a plurality of other power conversion devices 10 via a DC system 3 (3-1 to 3-8 in the figure). Hereinafter, the power conversion device 10 may be referred to as a conversion station.
　図１の例では、交流設備および変換所がそれぞれ５か所に点在し、変換所同士を接続する直流送電路が、計８区間（図中、区間３－１～３－８）が存在する場合の多端子直流送電システムである。交流電気設備２と変換所の個数および直流送電路の区間数や条数はこの限りでない。例えば、交流電気設備２と連系する少なくとも３つ以上の変換所を直流送電路２区間で接続した、ループ状あるいは非ループ状の直流送電システムまたは２端子直流送電システムに、本実施形態の処理等が適用されてもよい。 In the example of FIG. 1, AC equipment and conversion stations are scattered at five locations, and there are a total of eight sections (sections 3-1 to 3-8 in the figure) of DC transmission lines connecting the conversion stations. It is a multi-terminal DC power transmission system when The number of AC electrical equipment 2 and conversion stations, and the number of sections and lines of DC transmission lines are not limited to this. For example, the processing of the present embodiment is applied to a loop-shaped or non-loop-shaped DC power transmission system or a two-terminal DC power transmission system in which at least three or more conversion stations connected to the AC electrical equipment 2 are connected by two sections of the DC power transmission line. Etc. may be applied.
　図２は、電力変換装置１０の機能構成を中心に示す図である。直流母線２００（図中、２００Ｐ、２００Ｎ）に対して、並列に、電力変換装置１０および直流遮断器２１０（２１０－１、２１０－２）が電気線を介して接続されている。 FIG. 2 is a diagram focusing on the functional configuration of the power conversion device 10. A power converter 10 and a DC circuit breaker 210 (210-1, 210-2) are connected in parallel to the DC bus 200 (200P, 200N in the figure) via an electric line.
　電力変換装置１０は、例えば、電力変換器２０と、負荷装置８０と、制御装置１００とを備える。電力変換器２０と負荷装置８０とは電気線を介して並列に接続されている。電力変換器２０は、変圧器ＴＲと、複数のレグ３０（図中、３０－１～３０－３）とを有する。 The power converter 10 includes, for example, a power converter 20, a load device 80, and a control device 100. The power converter 20 and the load device 80 are connected in parallel via an electric wire. The power converter 20 has a transformer TR and a plurality of legs 30 (30-1 to 30-3 in the figure).
　交流電気設備２と各レグ３０の端子ＮＡＣとの間には、変圧器ＴＲが接続されている。変圧器ＴＲは、一次巻線と二次巻線との組を三相分備える。三相とは、例えば、交流のＵ相、交流のＶ相、および交流のＷ相である。変圧器ＴＲの一次巻線側には、交流のＵ相の交流電力と、交流のＶ相の交流電力と、交流のＷ相の交流電力とが、それぞれ供給される。変圧器ＴＲは、供給された交流電力を変圧して、変圧した交流電力を二次巻線側（レグ３０側）に出力する。 A transformer TR is connected between the AC electrical equipment 2 and the terminal NAC of each leg 30. The transformer TR includes a set of a primary winding and a secondary winding for three phases. The three phases are, for example, an alternating current U phase, an alternating current V phase, and an alternating current W phase. AC U-phase AC power, AC V-phase AC power, and AC W-phase AC power are supplied to the primary winding side of the transformer TR, respectively. The transformer TR transforms the supplied AC power and outputs the transformed AC power to the secondary winding side (leg 30 side).
　各レグ３０は、正側アーム４０Ｐ（４０Ｐ－１～４０Ｐ－３）と負側アーム４０Ｎ（４０Ｎ－１～４０Ｎ－３）とを含む。正側アーム４０Ｐと負側アーム４０Ｎとの間には、端子ＮＡＣが接続されている。図２の例では、レグ３０－１の端子ＮＡＣには変圧器ＴＲの二次巻線Ｕ相が接続され、レグ３０－２の端子ＮＡＣには変圧器ＴＲの二次巻線Ｖ相が接続され、レグ３０－３の端子ＮＡＣには変圧器ＴＲの二次巻線Ｗ相が接続される。 Each leg 30 includes a positive arm 40P (40P-1 to 40P-3) and a negative arm 40N (40N-1 to 40N-3). A terminal NAC is connected between the positive arm 40P and the negative arm 40N. In the example of FIG. 2, the secondary winding U phase of the transformer TR is connected to the terminal NAC of the leg 30-1, and the secondary winding V phase of the transformer TR is connected to the terminal NAC of the leg 30-2. Then, the W phase of the secondary winding of the transformer TR is connected to the terminal NAC of the leg 30-3.
　レグ３０の正側アーム４０Ｐにおいて、一以上のセル５０（例えば５０Ｐ－１－１～５０Ｐ－１－ｎ）が直列に接続される。「ｎ」は任意の自然数である。レグ３０の負側アーム４０Ｎにおいて、一以上のセル５０（例えば５０Ｎ－１－１～５０Ｎ－１－ｎ）が直列に接続される。正側アーム４０Ｐおよび負側アーム４０Ｎには、それぞれセル５０がＮ個（Ｎ≧２）直列に接続されている。セル５０は単位変換器として機能し、アーム４０は階段状の交流電圧等の任意の電圧を出力する。 In the positive arm 40P of the leg 30, one or more cells 50 (for example, 50P-1-1 to 50P-1-n) are connected in series. "N" is an arbitrary natural number. In the negative arm 40N of the leg 30, one or more cells 50 (for example, 50N-1-1 to 50N-1-n) are connected in series. N cells (N ≧ 2) are connected in series to the positive arm 40P and the negative arm 40N, respectively. The cell 50 functions as a unit converter, and the arm 40 outputs an arbitrary voltage such as a stepped AC voltage.
　上記の階段状の交流電圧の出力は、各セル５０が備えるスイッチング素子（図３参照）のスイッチング動作のタイミングがずらされることにより行われる。例えば、制御装置１００は、各セル５０に入力されるアーム電圧指令値Ｘ１に基づいてスイッチング素子を制御してスイッチング動作を制御する。各セル５０は、内部に有するセルコンデンサの電圧を検出し、セルコンデンサの電圧検出値（コンデンサ電圧検出値Ｘ２）を制御装置１００に出力する。セル５０および上記制御の内容の詳細については後述する。 The above-mentioned stepped AC voltage output is performed by shifting the timing of the switching operation of the switching element (see FIG. 3) included in each cell 50. For example, the control device 100 controls the switching element based on the arm voltage command value X1 input to each cell 50 to control the switching operation. Each cell 50 detects the voltage of the cell capacitor contained therein, and outputs the voltage detection value of the cell capacitor (capacitor voltage detection value X2) to the control device 100. Details of the cell 50 and the contents of the control will be described later.
　バッファリアクトルＬＢと電流センサＣＴは、正側アーム４０Ｐと直列に接続されている。バッファリアクトルＬＢと電流センサＣＴは、負側アーム４０Ｎと直列に接続されている。バッファリアクトルＬＢは、セル５０に流れる短絡電流を抑制する。電流センサＣＴは各バッファリアクトルＬＢに流れる電流を検出し、アーム電流検出値Ｘ３を制御装置１００に出力する。 The buffer reactor LB and the current sensor CT are connected in series with the positive arm 40P. The buffer reactor LB and the current sensor CT are connected in series with the negative arm 40N. The buffer reactor LB suppresses the short-circuit current flowing through the cell 50. The current sensor CT detects the current flowing through each buffer reactor LB and outputs the arm current detection value X3 to the control device 100.
　正側アーム４０Ｐおよび負側アーム４０Ｎのそれぞれにおいて、各セル５０の電圧が加算されて出力電圧が決定される。正側アーム４０Ｐの出力直流電圧は、交流端子ＮＡＣを基準にすると正の電圧である。正側アーム４０Ｐによって生成された正の直流電圧は、端子ＮＤＣＰに出力される。負側アーム４０Ｎの出力直流電圧は、交流端子ＮＡＣを基準にすると負の電圧である。負側アーム４０Ｎによって生成された負の直流電圧は、端子ＮＤＣＮに出力される。電力変換器２０は、端子ＮＤＣＰと端子ＮＤＣＮの間に直流電力を供給する。 In each of the positive side arm 40P and the negative side arm 40N, the voltage of each cell 50 is added to determine the output voltage. The output DC voltage of the positive arm 40P is a positive voltage with reference to the AC terminal NAC. The positive DC voltage generated by the positive arm 40P is output to the terminal NDCP. The output DC voltage of the negative arm 40N is a negative voltage with reference to the AC terminal NAC. The negative DC voltage generated by the negative arm 40N is output to the terminal NDCN. The power converter 20 supplies DC power between the terminal NDCP and the terminal NDCN.
　負荷装置８０は、例えば、抵抗体や、蓄電機能を有する装置等である。負荷装置８０は、動作状態において直流側電力を消費または蓄電することによって、電力変換器２０の直流側電力を調整する機能を有する。負荷装置８０は、電力変換器２０の直流側における正極線と負極線（または接地線）との間に接続される。負荷装置８０は端子ＮＤＣＰと端子ＮＤＣＮに接続され、入力される負荷装置動作指令Ｘ４に従って動作状態または停止状態に制御される。例えば、直流事故等によって電力変換器２０の交流側の電力に対し直流側の電力が増加した場合に各セル５０のエネルギー蓄積要素であるセルコンデンサが過充電され、セルコンデンサが過電圧になる場合がある。このとき負荷装置８０が動作状態になることで、直流側の電力を調整する。この調整により、交流側の電力と直流側の電力との均衡が維持されて、セルコンデンサの過電圧が回避される。負荷装置８０は、動作状態に応じて、動作状態または停止状態を示す負荷装置状態信号Ｘ５を出力する。 The load device 80 is, for example, a resistor, a device having a power storage function, or the like. The load device 80 has a function of adjusting the DC side electric power of the power converter 20 by consuming or storing the DC side electric power in the operating state. The load device 80 is connected between the positive electrode wire and the negative electrode wire (or the ground wire) on the DC side of the power converter 20. The load device 80 is connected to the terminal NDCP and the terminal NDCN, and is controlled to an operating state or a stopped state according to the input load device operation command X4. For example, when the power on the DC side increases with respect to the power on the AC side of the power converter 20 due to a DC accident or the like, the cell capacitor, which is an energy storage element of each cell 50, may be overcharged and the cell capacitor may become overvoltage. is there. At this time, when the load device 80 is put into the operating state, the electric power on the DC side is adjusted. By this adjustment, the balance between the power on the AC side and the power on the DC side is maintained, and the overvoltage of the cell capacitor is avoided. The load device 80 outputs a load device state signal X5 indicating an operating state or a stopped state according to the operating state.
　直流母線２００Ｐは端子ＮＤＣＰに接続され、直流母線２００Ｎは端子ＮＤＣＮに接続される。直流母線２００と直流母線２００に接続された直流系統３（直流送電路）との接点のうち少なくとも１つには直流遮断器２１０が接続される。制御装置１００は、直流遮断器２１０の開閉状態を制御可能である。直流遮断器２１０は、１つの直流遮断器であってもよいし、複数の直流遮断器を含んでもよい。例えば、直流遮断器２１０－１は直流母線２００Ｐと直流系統３との間に接続されている。直流遮断器２１０－２は直流母線２００Ｎと直流系統３との間に接続されている。直流遮断器２１０は、直流系統３を介して所定の変換所（第１変換所、第２変換所・・・）に接続される。直流遮断器２１０は、制御装置１００が出力する直流遮断機動作指令Ｘ６に応じて、開動作または閉動作し、開動作または閉動作したことを示す直流遮断器状態信号Ｘ７を制御装置１００に出力する。 The DC bus 200P is connected to the terminal NDCP, and the DC bus 200N is connected to the terminal NDCN. A DC circuit breaker 210 is connected to at least one of the contacts between the DC bus 200 and the DC system 3 (DC transmission line) connected to the DC bus 200. The control device 100 can control the open / closed state of the DC circuit breaker 210. The DC circuit breaker 210 may be one DC circuit breaker or may include a plurality of DC circuit breakers. For example, the DC circuit breaker 210-1 is connected between the DC bus 200P and the DC system 3. The DC circuit breaker 210-2 is connected between the DC bus 200N and the DC system 3. The DC circuit breaker 210 is connected to a predetermined conversion station (first conversion station, second conversion station, etc.) via the DC system 3. The DC circuit breaker 210 outputs the DC circuit breaker status signal X7 indicating that the open operation or the closed operation is performed and the open operation or the closed operation is performed in response to the DC circuit breaker operation command X6 output by the control device 100 to the control device 100. To do.
　直流帰路を大地帰路とするために端子ＮＤＣＮを接地する場合は、負側の直流母線２００Ｎや負側の直流母線２００Ｎに接続された直流遮断器２１０－２は省略されてもよい。 When the terminal NDCN is grounded so that the DC return route is the ground return route, the DC circuit breaker 210-2 connected to the negative side DC bus 200N or the negative side DC bus 200N may be omitted.
　制御装置１００は、ＣＰＵ（Central Processing Unit）などのプロセッサが、記憶装置に記憶されたプログラム（ソフトウェア）を実行することで実現される。制御装置１００は、ＬＳＩ（Large Scale Integration）やＡＳＩＣ（Application Specific Integrated Circuit）、ＦＰＧＡ（Field-Programmable Gate Array）、ＧＰＵ（Graphics Processing Unit）等のハードウェア（回路部：circuitryを含む）によって実現されていてもよいし、ソフトウェアとハードウェアの協働によって実現されていてもよい。プログラムは、予めＨＤＤ（Hard Disk Drive）やフラッシュメモリなどの記憶装置に格納されていてもよいし、ＤＶＤやＣＤ－ＲＯＭなどの着脱可能な記憶媒体に格納されており、記憶媒体がドライブ装置に装着されることでインストールされてもよい。 The control device 100 is realized by a processor such as a CPU (Central Processing Unit) executing a program (software) stored in the storage device. The control device 100 is realized by hardware (including a circuit unit: circuitry) such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and GPU (Graphics Processing Unit). It may be realized by the cooperation of software and hardware. The program may be stored in advance in a storage device such as an HDD (Hard Disk Drive) or a flash memory, or is stored in a removable storage medium such as a DVD or CD-ROM, and the storage medium is stored in the drive device. It may be installed by being attached.
　制御装置１００は、電力変換器２０からコンデンサ電圧検出値Ｘ２およびアーム電流検出値Ｘ３を取得し、取得したこれらの検出値に基づいて、所定の演算を行って各種操作量（アーム電圧指令値Ｘ１）を導出する。上記によって得られたアーム電圧指令値Ｘ１は各セル５０に送信される。 The control device 100 acquires the capacitor voltage detection value X2 and the arm current detection value X3 from the power converter 20, and based on these detected values, performs a predetermined calculation to perform various operation amounts (arm voltage command value X1). ) Is derived. The arm voltage command value X1 obtained as described above is transmitted to each cell 50.
　制御装置１００は、セル５０のコンデンサの電圧に基づいて、負荷装置８０に電力を消費または蓄電させるように負荷装置８０を制御する。制御装置１００は、負荷装置８０の動作または停止を決定するための演算を行い、演算結果に基づいて負荷装置動作指令Ｘ４を導出し、導出した負荷装置動作指令Ｘ４を負荷装置８０に送信する（詳細は後述する）。 The control device 100 controls the load device 80 so that the load device 80 consumes or stores electric power based on the voltage of the capacitor of the cell 50. The control device 100 performs an operation for determining the operation or stop of the load device 80, derives the load device operation command X4 based on the calculation result, and transmits the derived load device operation command X4 to the load device 80 ( Details will be described later).
　制御装置１００は、負荷装置８０の動作状態を示す負荷装置状態信号Ｘ５を、負荷装置８０から取得する。制御装置１００は、取得した負荷装置状態信号Ｘ５に基づいて、直流遮断器２１０の開閉動作を決定するための演算を行って直流遮断機動作指令Ｘ６を導出する。制御装置１００は、導出した直流遮断機動作指令Ｘ６を直流遮断器２１０に送信する。制御装置１００は、直流遮断器２１０の動作状態を示す直流遮断器状態信号Ｘ７を取得し、取得した直流遮断器状態信号Ｘ７に基づいて、直流遮断器２１０の開閉動作を決定するための演算を行う（詳細は後述する）。 The control device 100 acquires the load device status signal X5 indicating the operating state of the load device 80 from the load device 80. Based on the acquired load device status signal X5, the control device 100 performs an operation for determining the opening / closing operation of the DC circuit breaker 210 to derive the DC circuit breaker operation command X6. The control device 100 transmits the derived DC circuit breaker operation command X6 to the DC circuit breaker 210. The control device 100 acquires the DC circuit breaker status signal X7 indicating the operating state of the DC circuit breaker 210, and based on the acquired DC circuit breaker status signal X7, performs an operation for determining the opening / closing operation of the DC circuit breaker 210. (Details will be described later).
　図３は、セル５０の機能構成の一例を示す図である。セル５０は、例えば、ハーフブリッジ型のチョッパセルである。この場合、セル５０は、端子５０Ａ、端子５０Ｂと、スイッチング素子５２Ａと、スイッチング素子５２Ｂと、セルコンデンサ５４と、給電回路５６と、セル制御部５８と、帰還ダイオード６０Ａと、帰還ダイオード６０Ｂと、電圧センサＶＴとを備える。 FIG. 3 is a diagram showing an example of the functional configuration of the cell 50. The cell 50 is, for example, a half-bridge type chopper cell. In this case, the cell 50 includes a terminal 50A, a terminal 50B, a switching element 52A, a switching element 52B, a cell capacitor 54, a feeding circuit 56, a cell control unit 58, a feedback diode 60A, and a feedback diode 60B. It is equipped with a voltage sensor VT.
　端子５０Ａは、端子ＮＤＣＰまたは他のセル５０に接続され、端子５０Ｂは、他のセル５０または端子ＮＡＣに接続されている。スイッチング素子５２Ａと、スイッチング素子５２Ｂとは、ＩＧＢＴ（Insulated Gate Bipolar Transistor）やＭＯＳＦＥＴ（metal-oxide-semiconductor field-effect transistor）等の自己消弧型の半導体素子である。これらのスイッチング素子５２Ａおよびスイッチング素子５２Ｂは、例えば、直列に２個接続されている。 Terminal 50A is connected to terminal NDCP or other cell 50, and terminal 50B is connected to other cell 50 or terminal NAC. The switching element 52A and the switching element 52B are self-extinguishing semiconductor elements such as an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (metal-oxide-semiconductor field-effect transistor). Two of these switching elements 52A and 52B are connected in series, for example.
　帰還ダイオード６０Ａと、帰還ダイオード６０Ｂとは、直列に接続され、スイッチング素子５２Ａおよびスイッチング素子５２Ｂにそれぞれ逆並列に接続されている。端子５０Ａから延在する電気線は、直列に接続されたスイッチング素子５２Ａとスイッチング素子５２Ｂとの間、および直列に接続された帰還ダイオード６０Ａと帰還ダイオード６０Ｂとの間に接続される。 The feedback diode 60A and the feedback diode 60B are connected in series, and are connected to the switching element 52A and the switching element 52B in antiparallel, respectively. The electric wire extending from the terminal 50A is connected between the switching element 52A and the switching element 52B connected in series, and between the feedback diode 60A and the feedback diode 60B connected in series.
　セルコンデンサ５４は、直列に接続された２個のスイッチング素子５２Ａおよびスイッチング素子５２Ｂに並列に接続されている。 The cell capacitor 54 is connected in parallel to two switching elements 52A and 52B connected in series.
　給電回路５６は、セルコンデンサ５４に直接に接続される。給電回路５６は降圧回路である。給電回路５６は、セルコンデンサ５４により出力された電圧をセル制御部５８に出力することでセル制御部５８に電力を供給する。電圧センサＶＴは、セルコンデンサ５４の両端の電位差を検出し、検出値をセル制御部５８に出力する。スイッチング素子５２Ａおよび帰還ダイオード６０Ａの第１側（正端子側）は電圧センセＶＴの第１側（正端子側）に接続されている。スイッチング素子５２Ｂおよび帰還ダイオード６０Ｂの第２側（負端子側）は、端子５０Ｂから延在する電気線を介して、電圧センセＶＴの第２側（負端子側）に接続されている。 The power supply circuit 56 is directly connected to the cell capacitor 54. The power supply circuit 56 is a step-down circuit. The power supply circuit 56 supplies electric power to the cell control unit 58 by outputting the voltage output by the cell capacitor 54 to the cell control unit 58. The voltage sensor VT detects the potential difference between both ends of the cell capacitor 54 and outputs the detected value to the cell control unit 58. The first side (positive terminal side) of the switching element 52A and the feedback diode 60A is connected to the first side (positive terminal side) of the voltage sensation VT. The second side (negative terminal side) of the switching element 52B and the feedback diode 60B is connected to the second side (negative terminal side) of the voltage sensation VT via an electric wire extending from the terminal 50B.
　セル制御部５８は、制御装置１００により出力された制御信号に基づいてスイッチング素子５２を制御して直流母線２００に出力する電力を制御し、電圧センサＶＴにより検出された電圧を制御装置１００に提供する。セル制御部５８は、電圧センサＶＴにより検出された検出値と制御装置１００に出力されるアーム電圧指令値Ｘ１とを取得し、取得した情報に基づいて、各種演算（例えばＰＷＭ制御のための演算）を行う。制御装置１００は、ＰＷＭ制御のための演算結果に応じて、ゲート信号Ｇ１およびゲート信号Ｇ２を生成し、生成したゲート信号Ｇ１をスイッチング素子５２Ａのゲートに出力し、生成したゲート信号Ｇ２をスイッチング素子５２Ｂのゲートに出力する。制御装置１００により出力される制御信号には、セル５０の電力変換動作を停止させるための変換器停止指令ＥＳが含まれる場合がある。セル制御部５８は、変換器停止指令ＥＳを取得すると、各セル５０の電力変換動作を停止させる。セル制御部５８は、コンデンサ電圧検出値Ｘ２を制御装置１００に送信する。 The cell control unit 58 controls the switching element 52 based on the control signal output by the control device 100 to control the power output to the DC bus 200, and provides the voltage detected by the voltage sensor VT to the control device 100. To do. The cell control unit 58 acquires the detection value detected by the voltage sensor VT and the arm voltage command value X1 output to the control device 100, and based on the acquired information, various calculations (for example, a calculation for PWM control). )I do. The control device 100 generates a gate signal G1 and a gate signal G2 according to the calculation result for PWM control, outputs the generated gate signal G1 to the gate of the switching element 52A, and outputs the generated gate signal G2 to the switching element. Output to the gate of 52B. The control signal output by the control device 100 may include a converter stop command ES for stopping the power conversion operation of the cell 50. When the cell control unit 58 acquires the converter stop command ES, the cell control unit 58 stops the power conversion operation of each cell 50. The cell control unit 58 transmits the capacitor voltage detection value X2 to the control device 100.
　セル５０は、スイッチング素子５２Ａがオン制御されており、スイッチング素子５２Ｂがオフにされている場合にセルコンデンサ５４の電圧を出力する。セル５０は、スイッチング素子５２Ａがオフ制御されており、スイッチング素子５２Ｂがオンにされている場合にゼロ電圧を出力する。 The cell 50 outputs the voltage of the cell capacitor 54 when the switching element 52A is on-controlled and the switching element 52B is turned off. The cell 50 outputs a zero voltage when the switching element 52A is off-controlled and the switching element 52B is turned on.
　図３に示したハーフブリッジ回路に代えて、図４に示すようなフルブリッジ回路が用いられてもよい。フルブリッジ回路は、４つのスイッチング素子５２Ｃ、５２Ｄ、５２Ｅ、５２Ｆを含む。スイッチング素子５２Ｃとスイッチング素子５２Ｄとは直列に接続され、スイッチング素子５２Ｅとスイッチング素子５２Ｆとは直列に接続されている。スイッチング素子５２Ｃとスイッチング素子５２Ｄとの直列回路とスイッチング素子５２Ｅとスイッチング素子５２Ｆとの直列回路とは、並列に接続されている。スイッチング素子５２Ｃとスイッチング素子５２Ｄとに対して、直列に接続された帰還ダイオード６０Ｃ、６０Ｄが逆並列に接続されている。スイッチング素子５２Ｅとスイッチング素子５２Ｆとに対して、直列に接続された帰還ダイオード６０Ｅ、６０Ｆが逆並列に接続されている。端子５０Ａから延在する電力線は、スイッチング素子５２Ｃとスイッチング素子５２Ｄとの間に接続され、端子５０Ｂから延在する電力線は、スイッチング素子５２Ｅとスイッチング素子５２Ｆとの間に接続されている。スイッチング素子５２Ｃ、５２Ｅ、５２Ｄ、５２Ｆは、セル制御部５８により生成されたゲート信号に基づいて制御される。 A full bridge circuit as shown in FIG. 4 may be used instead of the half bridge circuit shown in FIG. The full bridge circuit includes four switching elements 52C, 52D, 52E, 52F. The switching element 52C and the switching element 52D are connected in series, and the switching element 52E and the switching element 52F are connected in series. The series circuit of the switching element 52C and the switching element 52D and the series circuit of the switching element 52E and the switching element 52F are connected in parallel. The feedback diodes 60C and 60D connected in series to the switching element 52C and the switching element 52D are connected in antiparallel. The feedback diodes 60E and 60F connected in series to the switching element 52E and the switching element 52F are connected in antiparallel. The power line extending from the terminal 50A is connected between the switching element 52C and the switching element 52D, and the power line extending from the terminal 50B is connected between the switching element 52E and the switching element 52F. The switching elements 52C, 52E, 52D, and 52F are controlled based on the gate signal generated by the cell control unit 58.
　図５は、制御装置１００が実行する処理の概要を説明するための図である。
　制御装置１００は、例えば［処理１］～［処理４］を行う。
　［処理１］は、制御装置１００が、セル５０のセルコンデンサ５４の電圧（コンデンサ電圧）に基づいて負荷装置８０を制御し、直流電力を消費または蓄電する処理である。これによりセルコンデンサ５４の過電圧が抑制される。
　［処理２］は、制御装置１００が、直流事故検出時に、制御演算に用いる直流電力演算量を抑制する処理である。これによりコンデンサ電圧の制御性が向上する。すなわち、コンデンサ電圧が適切な範囲に制御される。
　［処理３］は、制御装置１００が、直流電流値に基づいて直流事故を検出する処理である。これにより迅速に直流事故が検出される。
　［処理４］は、制御装置１００が、遮断器の状態と直流電流とに基づいて電力変換器２０を再起動させる処理である。これにより迅速に電力変換器２０が再起動する。以下、これらの処理について説明する。 FIG. 5 is a diagram for explaining an outline of the process executed by the control device 100.
The control device 100 performs, for example, [Process 1] to [Process 4].
[Process 1] is a process in which the control device 100 controls the load device 80 based on the voltage (capacitor voltage) of the cell capacitor 54 of the cell 50 to consume or store DC power. As a result, the overvoltage of the cell capacitor 54 is suppressed.
[Process 2] is a process in which the control device 100 suppresses the DC power calculation amount used for the control calculation when the DC accident is detected. This improves the controllability of the capacitor voltage. That is, the capacitor voltage is controlled within an appropriate range.
[Process 3] is a process in which the control device 100 detects a DC accident based on the DC current value. As a result, a DC accident is detected quickly.
[Process 4] is a process in which the control device 100 restarts the power converter 20 based on the state of the circuit breaker and the direct current. As a result, the power converter 20 is quickly restarted. Hereinafter, these processes will be described.
　［処理１］
　まず、変換所の直流側に接続される負荷装置８０の動作の詳細について図６を参照しながら説明する。図６は負荷装置８０の動作および停止を示す指令値を決定する処理を説明するための図である。 [Process 1]
First, the details of the operation of the load device 80 connected to the DC side of the conversion station will be described with reference to FIG. FIG. 6 is a diagram for explaining a process of determining a command value indicating the operation and stop of the load device 80.
　制御装置１００は、動作演算部Ａ１を含む。動作演算部Ａ１は、始動判定部Ａ２－１と、停止判定部Ａ２－２と、ＳＲ－ＦＦ部Ａ２－３とを備える。動作演算部Ａ１は、コンデンサ電圧に基づいて、各処理を行う。以下の説明では、コンデンサ電圧の平均値を用いて処理が行われるものとして説明する。コンデンサ電圧の平均値は、例えば図２に示した複数のセルで検出されるコンデンサ電圧の全平均値であってもよいし、所定のアーム４０（例えば４０－１）に含まれるコンデンサ電圧検出値Ｘ２の平均値であってもよい。 The control device 100 includes an operation calculation unit A1. The operation calculation unit A1 includes a start determination unit A2-1, a stop determination unit A2-2, and an SR-FF unit A2-3. The operation calculation unit A1 performs each process based on the capacitor voltage. In the following description, it is assumed that the processing is performed using the average value of the capacitor voltages. The average value of the capacitor voltage may be, for example, the total average value of the capacitor voltages detected in the plurality of cells shown in FIG. 2, or the capacitor voltage detection value included in the predetermined arm 40 (for example, 40-1). It may be the average value of X2.
　まず、始動判定部Ａ２－１は、コンデンサ電圧の平均値を取得し、取得したコンデンサ電圧の平均値の時間変化率を導出する（ステップＢ１）。例えば、始動判定部Ａ２－１は、コンデンサ電圧の平均値の毎サンプルごとに前回のサンプル値との差分を導出し、その導出結果に高周波ノイズ除去用のフィルタ演算処理を行って時間変化率を導出したり、移動平均処理などを行うことにより時間変化率を導出する。 First, the start determination unit A2-1 acquires the average value of the capacitor voltage and derives the time change rate of the acquired average value of the capacitor voltage (step B1). For example, the start determination unit A2-1 derives the difference from the previous sample value for each sample of the average value of the capacitor voltage, and performs filter calculation processing for high frequency noise removal on the derived result to determine the time change rate. The time change rate is derived by deriving or performing moving average processing.
　次に、始動判定部Ａ２－１は、求めた時間変化率を予め設定した閾値ΔＶｃと比較し、コンデンサ電圧の平均値の時間変化率がΔＶｃよりも大きい場合にはハイ、小さい場合にはローを出力する（ステップＢ２）。次に、始動判定部Ａ２－１は、コンデンサ電圧の平均値が閾値Ｖｔｈ（第１閾値）を超えたか否かを判定する（ステップＢ３）。閾値Ｖｔｈは、定格値以上に設定された値である。例えば、閾値Ｖｔｈを１ｐｕとすると、コンデンサ電圧の平均値が１ｐｕよりも高い場合、または１ｐｕに所定値を減算（または加算）した値よりも高い場合にはハイ、低い場合にはローが出力される。閾値△Ｖｃを超える電圧の時間変化率は、異常な電圧上昇が生じている状況に応じた電圧の変化率である。閾値Ｖｔｈを超える電圧は、過電圧が生じている状況に応じた電圧である。 Next, the start determination unit A2-1 compares the obtained time change rate with the preset threshold value ΔVc, and is high when the time change rate of the average value of the capacitor voltage is larger than ΔVc, and low when it is smaller. Is output (step B2). Next, the start determination unit A2-1 determines whether or not the average value of the capacitor voltages exceeds the threshold value Vth (first threshold value) (step B3). The threshold value Vth is a value set to be equal to or higher than the rated value. For example, when the threshold value Vth is 1 pu, high is output when the average value of the capacitor voltage is higher than 1 pu, or high is output when the average value is higher than the value obtained by subtracting (or adding) a predetermined value to 1 pu, and low is output when the value is lower. To. The time change rate of the voltage exceeding the threshold value ΔVc is the rate of change of the voltage according to the situation where the abnormal voltage rise occurs. The voltage exceeding the threshold value Vth is a voltage according to the situation where an overvoltage is occurring.
　次に、始動判定部Ａ２－１は、処理Ｂ２の出力信号と処理Ｂ３の出力信号の論理積を導出する（ステップＢ４）。処理Ｂ２の出力信号と処理Ｂ３の出力信号とがハイの場合、ステップＢ４の処理でハイが出力され、処理Ｂ２の出力信号または処理Ｂ３の出力信号とがローの場合、ステップＢ４の処理でローが出力される。始動判定部Ａ２－１は、ステップＢ４で出力された信号が連続でハイ状態である連続時間を出力し、ステップＢ４の処理で出力される信号がローになった場合には出力をゼロにリセットする（ステップＢ５）。 Next, the start determination unit A2-1 derives the logical product of the output signal of the process B2 and the output signal of the process B3 (step B4). If the output signal of process B2 and the output signal of process B3 are high, high is output in the process of step B4, and if the output signal of process B2 or the output signal of process B3 is low, the process of step B4 is low. Is output. The start determination unit A2-1 outputs a continuous time in which the signal output in step B4 is continuously in a high state, and resets the output to zero when the signal output in the process of step B4 becomes low. (Step B5).
　始動判定部Ａ２－１は、処理Ｂ５で出力された連続時間と、予め設定された規定時間Ｔ１との大小を比較する（ステップＢ６）。始動判定部Ａ２－１は、処理Ｂ５で出力された連続時間が規定時間Ｔ１よりも長い場合にはハイを出力し、短い場合にはローを出力する。上述した処理の結果、始動判定部Ａ２－１は、例えば直流事故などによってコンデンサ電圧の平均値が連続して閾値Ｖｔｈを超え、急増している場合にはハイ、それ以外の場合にはローを出力する。 The start determination unit A2-1 compares the magnitude of the continuous time output in the process B5 with the preset predetermined time T1 (step B6). The start determination unit A2-1 outputs high when the continuous time output in process B5 is longer than the specified time T1, and outputs low when it is shorter. As a result of the above-mentioned processing, the start determination unit A2-1 sets high when the average value of the capacitor voltage continuously exceeds the threshold value Vth due to a DC accident or the like and rapidly increases, and low in other cases. Output.
　停止判定部Ａ２－２は、コンデンサ電圧の平均値と予め設定した閾値Ｖｃｈとの大小を比較する（ステップＢ７）。停止判定部Ａ２－２は、コンデンサ電圧の平均値が閾値Ｖｃｈよりも小さい場合にはハイ、コンデンサ電圧の平均値が閾値Ｖｃｈよりも大きい場合にはローを出力する。閾値Ｖｃｈ（第２閾値）は、コンデンサ電圧が閾値Ｖｔｈに相当する、または閾値Ｖｔｈよりも小さい定格レベル以下の電圧である。 The stop determination unit A2-2 compares the magnitude of the average value of the capacitor voltage and the preset threshold value Vch (step B7). The stop determination unit A2-2 outputs high when the average value of the capacitor voltage is smaller than the threshold value Vch, and outputs low when the average value of the capacitor voltage is larger than the threshold value Vch. The threshold value Vch (second threshold value) is a voltage below the rated level at which the capacitor voltage corresponds to the threshold value Vth or is smaller than the threshold value Vth.
　ＳＲ－ＦＦ部Ａ２－３が、始動判定部Ａ２－１の出力信号と停止判定部Ａ２－２の出力信号を用いて、負荷装置動作指令Ｘ４を生成する（ステップＢ８）。ＳＲ－ＦＦ部Ａ２－３は、始動判定部Ａ２－１の出力信号をＳＲ－ＦＦ部Ａ２－３のセット端子（Ｓ）に入力し、停止判定部Ａ２－２の出力信号をＳＲ－ＦＦ部Ａ２－３のリセット端子（Ｒ）に入力する。この結果、負荷装置動作指令Ｘ４は、直流事故などによってコンデンサ電圧の平均値が規定時間Ｔ１の間、閾値Ｖｔｈを超え急増した場合にはハイとなり、コンデンサ電圧の平均値が閾値Ｖｃｈ以下になった場合にロー信号となる。 The SR-FF unit A2-3 uses the output signal of the start determination unit A2-1 and the output signal of the stop determination unit A2-2 to generate the load device operation command X4 (step B8). The SR-FF unit A2-3 inputs the output signal of the start determination unit A2-1 to the set terminal (S) of the SR-FF unit A2-3, and inputs the output signal of the stop determination unit A2-2 to the SR-FF unit. Input to the reset terminal (R) of A2-3. As a result, the load device operation command X4 becomes high when the average value of the capacitor voltage exceeds the threshold value Vth and suddenly increases during the specified time T1 due to a DC accident or the like, and the average value of the capacitor voltage becomes equal to or less than the threshold value Vch. In some cases, it becomes a low signal.
　負荷装置８０は、上記の処理によって生成された負荷装置動作指令Ｘ４に従って動作または停止する。負荷装置８０は、負荷装置動作指令Ｘ４がハイを示す指令である場合に動作して、負荷装置動作指令Ｘ４がローを示す指令である場合に停止する。負荷装置８０が動作することによってコンデンサ電圧の上昇が抑制されて、過電圧により電力変換器２０が停止するのを防止する。 The load device 80 operates or stops in accordance with the load device operation command X4 generated by the above process. The load device 80 operates when the load device operation command X4 is a command indicating high, and stops when the load device operation command X4 is a command indicating low. By operating the load device 80, an increase in the capacitor voltage is suppressed, and the power converter 20 is prevented from stopping due to an overvoltage.
　図７は、動作演算部Ａ１の動作とコンデンサ電圧の平均値と電圧変化率との関係の一例を示す図である。図７では閾値Ｖｃｈは１ｐｕである。時刻ｔにおいて、事故が発生すると、時刻ｔから時刻ｔ＋１の間で、事故の影響により、一時的にコンデンサ電圧の平均値が低下し、コンデンサ電圧の変化率が０ｐｕ／ｓに対してマイナスになる。 FIG. 7 is a diagram showing an example of the relationship between the operation of the operation calculation unit A1 and the average value of the capacitor voltage and the voltage change rate. In FIG. 7, the threshold value Vch is 1 pu. When an accident occurs at time t, the average value of the capacitor voltage temporarily decreases between time t and time t + 1 due to the influence of the accident, and the rate of change of the capacitor voltage becomes negative with respect to 0 pu / s. ..
　時刻ｔ＋１において、コンデンサ電圧の平均値が上昇すると、コンデンサ電圧の変化率が上昇し、コンデンサ電圧の変化率は閾値△Ｖｃ以上となり、ステップＢ２の処理でハイの信号が出力される。時刻ｔ＋２において、コンデンサ電圧の平均値が閾値Ｖｔｈを超えると、ステップＢ３の処理で、ハイの信号が出力される。 At time t + 1, when the average value of the capacitor voltage rises, the rate of change of the capacitor voltage rises, the rate of change of the capacitor voltage becomes the threshold value ΔVc or more, and a high signal is output in the process of step B2. When the average value of the capacitor voltage exceeds the threshold value Vth at time t + 2, a high signal is output in the process of step B3.
　時刻ｔ＋２から時刻ｔ＋３の間、ステップＢ２およびＢ３でハイの信号が出力されているため、ステップＢ４の処理でハイの信号が出力される。このハイの信号の出力時間が規定時間Ｔ１を超えた時刻ｔ＋３において、ステップＢ６の処理でハイの信号が出力され、負荷装置８０を動作させるための信号を生成され、生成された信号が負荷装置８０に出力される。 Since the high signal is output in steps B2 and B3 between the time t + 2 and the time t + 3, the high signal is output in the process of step B4. At time t + 3 when the output time of this high signal exceeds the specified time T1, the high signal is output in the process of step B6, a signal for operating the load device 80 is generated, and the generated signal is the load device. It is output to 80.
　時刻ｔ＋３において、コンデンサ電圧の平均値がピークとなり、その後、コンテンツ電圧の平均値が減少し続けて、時刻ｔ＋４において、コンデンサ電圧の平均値が閾値Ｖｃｈ以下となると、ステップＢ７でハイの信号が出力され、ステップＢ８の処理で負荷装置８０の動作を停止させるための信号が生成され、生成された信号が負荷装置８０に出力される。 At time t + 3, the average value of the capacitor voltage peaks, then the average value of the content voltage continues to decrease, and at time t + 4, when the average value of the capacitor voltage falls below the threshold Vch, a high signal is output in step B7. Then, in the process of step B8, a signal for stopping the operation of the load device 80 is generated, and the generated signal is output to the load device 80.
　上述したように、制御装置１００は、電力変換器２０に含まれるコンデンサの電圧に基づいて、負荷装置８０に電力を消費または蓄電させるように負荷装置８０を制御することにより、セルコンデンサ５４の過電圧が抑制される。この結果、制御装置１００は、直流送電システム１の状況に応じて、電力変換器２０をより適切に制御することができる。 As described above, the control device 100 controls the load device 80 so as to consume or store electric power in the load device 80 based on the voltage of the capacitor included in the power converter 20, thereby causing the overvoltage of the cell capacitor 54. Is suppressed. As a result, the control device 100 can more appropriately control the power converter 20 according to the situation of the DC power transmission system 1.
　［処理２］
　図８は、直流事故時に行われる操作量の演算に関する処理を説明するための図である。制御装置１００の内部で制御演算が行われ、セル５０を制御するための操作量が導出される。制御装置１００は、コンデンサ電圧（直流電圧）と自変換所の直流側に流れる直流電流量とに基づいて直流電力量を導出する。制御装置１００は、この直流電力量をフィードフォワード量として利用して、各種の制御演算を行う。直流電力量は、後述する処理３の直流電流に基づいて導出される。 [Processing 2]
FIG. 8 is a diagram for explaining a process related to the calculation of the manipulated variable performed at the time of a DC accident. A control calculation is performed inside the control device 100, and an operation amount for controlling the cell 50 is derived. The control device 100 derives a DC power amount based on the capacitor voltage (DC voltage) and the amount of DC current flowing on the DC side of the self-converting station. The control device 100 uses this DC power amount as a feedforward amount to perform various control calculations. The DC power amount is derived based on the DC current of the process 3 described later.
　制御装置１００は、直流電力算出部１１０と、コンデンサ電圧制御部１１２と、有効電流指令値算出部１１４と、交流電流制御部１１６と、リミッタ１１８と、切替部１２０とを備える。図８に示すように、コンデンサ電圧制御部１１２は、コンデンサ電圧制御に関する出力Ｐｃ_ｒｅｆを加算器に出力し（ステップＢ１０）、直流電力算出部１１０は、フィードフォワード量である直流電力量Ｐｄｃ_ｆｆを加算器に出力する（ステップＢ１１）。加算器は、コンデンサ電圧制御部１１２が出力した出力Ｐｃ_ｒｅｆと、直流電力算出部１１０が出力した直流電力量Ｐｄｃ_ｆｆとを加算する（ステップＢ１２）。加算結果は、有効電流指令値算出部１１４に入力される。有効電流指令値算出部Ｂ１２は、出力Ｉｄ_ｒｅｆを交流電流制御部１１６に出力する（ステップＢ１５）。交流電流制御部１１６は、ステップＢ１５の処理で出力された出力Ｉｄ_ｒｅｆを有効電流の制御指令値として利用する（ステップＢ１６）。 The control device 100 includes a DC power calculation unit 110, a capacitor voltage control unit 112, an effective current command value calculation unit 114, an AC current control unit 116, a limiter 118, and a switching unit 120. As shown in FIG. 8, the capacitor voltage control unit 112 outputs the output Pc_ref related to the capacitor voltage control to the adder (step B10), and the DC power calculation unit 110 uses the DC power amount Pdc_ff, which is the feed forward amount, as the adder. Output (step B11). The adder adds the output Pc_ref output by the capacitor voltage control unit 112 and the DC power amount Pdc_ff output by the DC power calculation unit 110 (step B12). The addition result is input to the effective current command value calculation unit 114. The effective current command value calculation unit B12 outputs the output Id_ref to the AC current control unit 116 (step B15). The AC current control unit 116 uses the output Id_ref output in the process of step B15 as the control command value of the effective current (step B16).
　直流事故が発生した場合には、直流電力量Ｐｄｃ_ｆｆが高周波で振動的に変動し、有効電流指令値算出部Ｂ１２の出力Ｉｄ_ｒｅｆが乱される。これが原因となり、有効電流制御が悪影響を受け、結果的にコンデンサ電圧の制御性が悪化することがある。そこで、直流事故を検出している間、直流事故検出信号Ｘ８に応じた切替部１２０の処理によって、直流電力算出部１１０の出力にリミッタ１１８が処理を行う（ステップＢ１３、Ｂ１４）。 When a DC accident occurs, the DC power amount Pdc_ff vibrates at high frequencies, and the output Id_ref of the effective current command value calculation unit B12 is disturbed. As a result, the effective current control may be adversely affected, and as a result, the controllability of the capacitor voltage may deteriorate. Therefore, while the DC accident is being detected, the limiter 118 processes the output of the DC power calculation unit 110 by processing the switching unit 120 in response to the DC accident detection signal X8 (steps B13 and B14).
　直流事故検出信号Ｘ８は、直流側で事故が発生している場合にはハイ、直流側が健全である場合にはローとなる。直流事故検出信号Ｘ８は、前述した図２の制御装置１００によって与えられたり、後述する方法によって直流電流値に基づいて生成されたりする。リミッタ１１８が用いる上限値および下限値は、例えば変換器の定格容量に準じた値である。あるいは、両方にゼロを用いる。これによって直流事故時の直流電力量Ｐｄｃ_ｆｆは制限されたり、無効化されたりするので、コンデンサ電圧の制御性悪化が抑制される。 The DC accident detection signal X8 is high when an accident has occurred on the DC side and low when the DC side is sound. The DC accident detection signal X8 is given by the control device 100 of FIG. 2 described above, or is generated based on the DC current value by a method described later. The upper limit value and the lower limit value used by the limiter 118 are, for example, values according to the rated capacity of the converter. Alternatively, use zero for both. As a result, the DC power amount Pdc_ff at the time of a DC accident is limited or invalidated, so that deterioration of the controllability of the capacitor voltage is suppressed.
　このように制御装置１００が、直流系統で事故が発生したことを示す信号を取得していない場合には、直流側電力の算出量に基づいて、電力変換器２０を制御するための制御信号を生成し、直流系統で事故が発生したことを示す信号を取得した場合には、直流側電力の算出量を制限した値に基づいて、制御信号を生成することにより、直流送電システム１の状況に応じて、電力変換器２０をより適切に制御することができる。 When the control device 100 does not acquire a signal indicating that an accident has occurred in the DC system in this way, a control signal for controlling the power converter 20 is generated based on the calculated amount of the DC side power. When a signal is generated and indicates that an accident has occurred in the DC system, a control signal is generated based on a value that limits the calculated amount of DC side power, so that the situation of the DC transmission system 1 is reached. Correspondingly, the power converter 20 can be controlled more appropriately.
　［処理３］
　図９は、直流系統３の事故状態と健全状態を検知するための状態検出部Ａ１１の処理に関するブロック図である。状態検出部Ａ１１の電流急増検出部Ａ１２は、入力された直流電流値Ｉｄｃを基に演算処理を行う。状態検出部Ａ１１の状態判定部Ａ１３は、電流急増検出部Ａ１２の出力を基に演算処理を行う。状態検出部Ａ１１のＳＲ－ＦＦ部は、電流急増検出部Ａ１２の演算結果と、状態判定部Ａ１３の演算結果とに基づいて、直流系統３が健全状態であるか、事故状態であるかを示す直流事故検出信号Ｘ８を出力する。 [Processing 3]
FIG. 9 is a block diagram relating to the processing of the state detection unit A11 for detecting the accident state and the sound state of the DC system 3. The current rapid increase detection unit A12 of the state detection unit A11 performs arithmetic processing based on the input DC current value Idc. The state determination unit A13 of the state detection unit A11 performs arithmetic processing based on the output of the current rapid increase detection unit A12. The SR-FF unit of the state detection unit A11 indicates whether the DC system 3 is in a sound state or an accident state based on the calculation result of the current rapid increase detection unit A12 and the calculation result of the state determination unit A13. The DC accident detection signal X8 is output.
　ここで直流電流とは、自変換所の直流側に流れる電流のことである。例えば、制御装置１００は、例えば、下記の手法で直流電流値Ｉｄｃを算出する。
（１）制御装置１００が、下記の式（１）のように各アームから出力されるアーム電流の総和の半分の量を求める。
（iarmpu＋iarmnu＋iarmpv＋iarmnv＋iarmpw＋iarmnw）／２・・・式（１） Here, the direct current is the current flowing on the direct current side of the conversion station. For example, the control device 100 calculates the DC current value Idc by the following method, for example.
(1) The control device 100 obtains half the total amount of arm currents output from each arm as in the following equation (1).
(Iarmpu ＋ iarmnu ＋ iarmpv ＋ iarmnv ＋ iarmpw ＋ iarmnw) / 2 ・ ・ ・ Equation (1)
　アーム電流である、iarmpu、iarmnu、iarmpv、iarmnv、iarmpw、iarmnwは、それぞれ正側アーム４０Ｐ－１、負側アーム４０Ｎ－１、正側アーム４０Ｐ－２、負側アーム４０Ｎ－２、正側アーム４０Ｐ－３、負側アーム４０Ｎ－３から出力される電流である。アーム電流は、不図示の電流センサにより検出されてもよいし、制御装置１００が、セル５０の制御に関する演算結果に基づいて導出されてもよい。 The arm currents iarmpu, iarmnu, iarmpv, iarmnv, iarmpw, and iarmnw are the positive arm 40P-1, the negative arm 40N-1, the positive arm 40P-2, the negative arm 40N-2, and the positive arm, respectively. This is the current output from 40P-3 and the negative arm 40N-3. The arm current may be detected by a current sensor (not shown), or the control device 100 may be derived based on the calculation result regarding the control of the cell 50.
（２）制御装置１００は、正側アーム４０Ｐの各相の総和iarmpu＋iarmpv＋iarmpwを求める。
（３）制御装置１００は、負側アーム４０Ｎの各相の総和iarmnu＋iarmnv＋iarmnwを求める。
（４）制御装置１００は、直流遮断器２１０に流れる電流を検出し、接点を共有する線路の電流の各和を求める。
（５）制御装置１００は、後述の２レベル変換器のように電力変換器２０の直流側にエネルギーバッファとしてのコンデンサを有し直流側の電圧を検出している場合、交流側の有効電力を直流電圧で除算することによって直流電流を求める。交流側の有効電力は、例えば、電流センサＣＴの検知結果や、電流センサＶＴの検知結果等に基づいて導出してもよい。 (2) The control device 100 obtains the total sum iarmpu + iarmpv + iarmpw of each phase of the positive arm 40P.
(3) The control device 100 obtains the total sum iarmnu + iarmnv + iarmnw of each phase of the negative arm 40N.
(4) The control device 100 detects the current flowing through the DC circuit breaker 210 and obtains the sum of the currents of the lines sharing the contact.
(5) When the control device 100 has a capacitor as an energy buffer on the DC side of the power converter 20 and detects the voltage on the DC side as in the two-level converter described later, the active power on the AC side is used. The DC current is obtained by dividing by the DC voltage. The active power on the AC side may be derived based on, for example, the detection result of the current sensor CT, the detection result of the current sensor VT, or the like.
　電流急増検出部Ａ１２では、直流電流値Ｉｄｃの絶対値を算出する（ステップＢ２０）。電流急増検出部Ａ１２は、ステップＢ１６で出力された直流電流値Ｉｄｃの絶対値の時間変化率を演算する（ステップＢ２１）。時間変化率を求める方法としては、毎サンプルごとに前回サンプル値との差分を算出し、その結果に高周波ノイズ除去用のフィルタ演算処理を行い算出する方法や、移動平均処理などを行う方法がある。 The current rapid increase detection unit A12 calculates the absolute value of the DC current value Idc (step B20). The current rapid increase detection unit A12 calculates the time change rate of the absolute value of the DC current value Idc output in step B16 (step B21). As a method of obtaining the time change rate, there are a method of calculating the difference from the previous sample value for each sample and performing filter calculation processing for high frequency noise removal on the result, and a method of performing moving average processing and the like. ..
　電流急増検出部Ａ１２は、ステップＢ２１で出力された時間変化率と、予め設定された閾値ΔＩｄｃとの大小を比較する（ステップＢ２２）。ステップＢ２１で出力された時間変化率が閾値ΔＩｄｃよりも大きい場合はハイ、小さい場合にはローが出力される。閾値ΔＩｄｃは、通常運転時に設定される直流電流の時間変化率よりも大きい値に設定される。閾値ΔＩｄｃは、例えば０．１ｐｕ／ｍｓである。 The current rapid increase detection unit A12 compares the magnitude of the time change rate output in step B21 with the preset threshold value ΔIdc (step B22). If the time change rate output in step B21 is larger than the threshold value ΔIdc, high is output, and if it is smaller than the threshold value ΔIdc, low is output. The threshold value ΔIdc is set to a value larger than the time change rate of the direct current set during normal operation. The threshold value ΔIdc is, for example, 0.1 pu / ms.
　事故状態の検知には、直流電流値Ｉｄｃが直接用いられてもよい。例えば、直流電流値が閾値と比較されることで、直流電流の異常増加から事故状態であることが検知される。この場合、閾値は、定格運転レベルよりも高い値に設定されている。しかし、時間変化率を用いることによって、事故状態をより早く検知することができる。 The DC current value Idc may be directly used for detecting the accident state. For example, by comparing the DC current value with the threshold value, it is detected that an accident state is caused by an abnormal increase in the DC current. In this case, the threshold value is set to a value higher than the rated operation level. However, by using the time change rate, the accident state can be detected earlier.
　状態判定部Ａ１３は、電力急増検出部Ａ１２により出力された信号に対して否定演算を行う（ステップＢ２３）。状態判定部Ａ１３は、ステップＢ２３で否定演算された信号が連続でハイ状態である時間を演算する（ステップＢ２４）。状態判定部Ａ１３は、電力急増検出部Ａ１２により出力される信号がローになった場合には出力をゼロにリセットする。 The state determination unit A13 performs a negative operation on the signal output by the power rapid increase detection unit A12 (step B23). The state determination unit A13 calculates the time during which the negatively calculated signal in step B23 is continuously in the high state (step B24). The state determination unit A13 resets the output to zero when the signal output by the power rapid increase detection unit A12 becomes low.
　状態判定部Ａ１３は、ステップＢ２４における処理結果と、予め設定された規定時間Ｔ２との大小を比較する（ステップＢ２５）。ステップＢ２５における処理結果に係る時間が規定時間Ｔ２よりも長い場合にはハイ、短い場合にはローが出力される。 The state determination unit A13 compares the magnitude of the processing result in step B24 with the preset predetermined time T2 (step B25). High is output when the time related to the processing result in step B25 is longer than the specified time T2, and low is output when the time is shorter than the specified time T2.
　次に、ＳＲ－ＦＦ部は、電流急増検出部Ａ１２により出力された信号と、状態判定部Ａ１３により出力された信号とを用いて、直流事故検出信号Ｘ８を生成する（ステップＢ２６）。ステップＢ２５では、電流急増検出部Ａ１２により出力された信号がＳＲ－ＦＦ部のセット端子（Ｓ）に入力され、状態判定部Ａ１３により出力された信号がＳＲ－ＦＦのリセット端子（Ｒ）に入力される。この結果、直流事故検出信号Ｘ８は、直流事故などによって直流側電流が急増し、直流電流の時間変化率が閾値ΔＩｄｃを超過した場合にはハイ、規定時間Ｔ２の間、直流電流の時間変化率が閾値ΔＩｄｃ以下になった場合にローとなる。上記の処理によって、素早く直流事故が検知される。 Next, the SR-FF unit generates a DC accident detection signal X8 using the signal output by the current rapid increase detection unit A12 and the signal output by the state determination unit A13 (step B26). In step B25, the signal output by the current rapid increase detection unit A12 is input to the set terminal (S) of the SR-FF unit, and the signal output by the state determination unit A13 is input to the reset terminal (R) of the SR-FF. Will be done. As a result, the DC accident detection signal X8 is high when the DC side current suddenly increases due to a DC accident or the like and the time change rate of the DC current exceeds the threshold value ΔIdc, and the time change rate of the DC current during the specified time T2. Is low when the value is equal to or less than the threshold value ΔIdc. By the above processing, a DC accident is quickly detected.
　このように、制御装置１００は、直流側の電流変化率が規定値よりも大きい場合に、直流側が事故状態であるとことを検知し、直流側の電流変化率が規定値以下になった場合に直流側が事故状態でなくなったことを検知することで、より迅速に事故の状態を検知することができる。そして、制御装置１００は、事故状態の検知結果に基づいて、迅速に電力変換器２０を制御することができる。例えば、制御装置１００は、処理２で説明したように、事故状態が検知された場合、直流電力の算出量を制限して、セル５０を制御するための制御信号を生成する。この結果、制御装置１００は、迅速、且つより確実にコンデンサ電圧を適切な状態に制御することができる。更に、制御装置１００は、事故状態が検知されなくなった場合、迅速に直流電力量の制限を解除することができる。 In this way, when the current change rate on the DC side is larger than the specified value, the control device 100 detects that the DC side is in an accident state, and when the current change rate on the DC side becomes equal to or less than the specified value. By detecting that the DC side is no longer in the accident state, the accident state can be detected more quickly. Then, the control device 100 can quickly control the power converter 20 based on the detection result of the accident state. For example, as described in Process 2, when an accident state is detected, the control device 100 limits the calculated amount of DC power and generates a control signal for controlling the cell 50. As a result, the control device 100 can quickly and more reliably control the capacitor voltage to an appropriate state. Further, the control device 100 can quickly release the limitation on the amount of DC power when the accident state is no longer detected.
　［処理４］
　図１０は、事故除去後に電力変換器２０がスイッチング動作を再開するか否かが決定される処理に関するブロック図である。制御装置１００の再起動判定部Ａ２０は、ゲートブロック中において、自変換所の直流遮断器２１０の開閉状態信号と直流電流とを用いて、電力変換器２０のスイッチング動作を再開することができるか否かを判定する。以下、再起動判定部Ａ２０の処理について説明する。 [Process 4]
FIG. 10 is a block diagram relating to a process for determining whether or not the power converter 20 restarts the switching operation after the accident is eliminated. Can the restart determination unit A20 of the control device 100 restart the switching operation of the power converter 20 in the gate block by using the open / closed state signal of the DC circuit breaker 210 of the own conversion station and the DC current? Judge whether or not. Hereinafter, the processing of the restart determination unit A20 will be described.
　自変換所の直流側と直流系統３との間に少なくとも１つの有効な送電経路が形成されている場合、送電可否判定部Ａ２１は、ハイの信号を出力する。例えば、以下のような構成が採用されてもよい。再起動判定部Ａ２０の送電可否判定部Ａ２１は、自変換所の直流遮断器２１０－１と直流遮断器２１０－２とのうち一方または双方の直流遮断器状態信号Ｘ７を論理和に入力する（ステップＢ３０）。このとき、直流遮断器状態信号はハイが開極状態、ローが閉極状態を示すものとする。次に、送電可否判定部Ａ２１は、ステップＢ３０の処理で出力された信号に対して否定演算を行う（ステップＢ３１）。これにより、直流遮断器２１０のいずかが閉状態であり、直流母線２００と直流系統３とが電気的に接続されている状態の場合にハイの信号が出力される。直流遮断器２１０のすべてが開状態であり、直流母線２００と直流系統３とが電気的に切断されている状態の場合にローの信号が出力される。 When at least one effective power transmission path is formed between the DC side of the self-conversion station and the DC system 3, the power transmission availability determination unit A21 outputs a high signal. For example, the following configuration may be adopted. The power transmission availability determination unit A21 of the restart determination unit A20 inputs the DC circuit breaker status signal X7 of one or both of the DC circuit breaker 210-1 and the DC circuit breaker 210-2 of the own conversion station to the OR (OR). Step B30). At this time, in the DC circuit breaker state signal, high indicates an open pole state and low indicates a closed pole state. Next, the power transmission availability determination unit A21 performs a negative operation on the signal output in the process of step B30 (step B31). As a result, a high signal is output when any of the DC circuit breakers 210 is in the closed state and the DC bus 200 and the DC system 3 are electrically connected. A low signal is output when all of the DC circuit breakers 210 are in the open state and the DC bus 200 and the DC system 3 are electrically disconnected.
　再起動判定部Ａ２０のゼロ電流判定部Ａ２２は、直流電流値Ｉｄｃに基づいて直流電流が概略ゼロであることを検出する。まず、ゼロ電流判定部Ａ２２は、直流電流値Ｉｄｃの絶対値を演算する（ステップＢ３２）。次に、ゼロ電流判定部Ａ２２は、ステップＢ３２の処理結果とニアゼロＩＺとの大小を比較する（ステップＢ３３）。直流電流がニアゼロＩＺよりも小さい場合にハイ、大きい場合にはローが出力される。ここで、ニアゼロＩＺは、直流電流が流れていないことを判定するための信号で、０．０１ｐｕなどのゼロに近い値を示す信号である。 The zero current determination unit A22 of the restart determination unit A20 detects that the DC current is substantially zero based on the DC current value Idc. First, the zero current determination unit A22 calculates the absolute value of the DC current value Idc (step B32). Next, the zero current determination unit A22 compares the magnitude of the processing result of step B32 with the near zero IZ (step B33). High is output when the DC current is smaller than Near Zero IZ, and low is output when the DC current is larger. Here, the near zero IZ is a signal for determining that no direct current is flowing, and is a signal showing a value close to zero such as 0.01pu.
　次に、ゼロ電流判定部Ａ２２は、ステップＢ３３で出力された出力信号が連続でハイ状態である時間を演算する（ステップＢ３４）。ステップＢ３３の出力信号がローになった場合にはステップＢ３４の出力はゼロにリセットされる。 Next, the zero current determination unit A22 calculates the time during which the output signal output in step B33 is continuously in the high state (step B34). When the output signal of step B33 becomes low, the output of step B34 is reset to zero.
　ゼロ電流判定部Ａ２２は、ステップＢ３４における処理結果と、予め設定された規定時間Ｔ３との大小を比較する（ステップＢ３５）。ステップＢ３５の処理結果が規定時間Ｔ３よりも長い場合にはハイ、短い場合にはローが出力される。例えば、規定時間Ｔ３は１ｍｓ程度の時間である。これにより、潮流反転などにより一時的に直流電流がゼロクロスする場合などの誤判定が回避される。 The zero current determination unit A22 compares the magnitude of the processing result in step B34 with the preset predetermined time T3 (step B35). If the processing result of step B35 is longer than the specified time T3, high is output, and if it is shorter, low is output. For example, the specified time T3 is a time of about 1 ms. As a result, erroneous determination such as when the direct current temporarily crosses zero due to tidal current reversal or the like is avoided.
　再起動判定部Ａ２０は、送電可否判定部Ａ２１により出力された信号と、ゼロ電流判定部Ａ２２により出力された信号との論理積を演算する（ステップＢ３６）。次に、再起動判定部Ａ２０は、ステップＢ３６の処理結果に対して、ポジティブエッジ検出処理を行って再起動信号を出力する（ステップＢ３７）。すなわち、再起動判定部Ａ２０は、ステップＢ３６で出力された出力信号がローからハイに変化した瞬間のみにパルス状の再起動信号を出力する。 The restart determination unit A20 calculates the logical product of the signal output by the power transmission availability determination unit A21 and the signal output by the zero current determination unit A22 (step B36). Next, the restart determination unit A20 performs positive edge detection processing on the processing result of step B36 and outputs a restart signal (step B37). That is, the restart determination unit A20 outputs a pulsed restart signal only at the moment when the output signal output in step B36 changes from low to high.
　再起動信号は、ステップＢ３６で出力された信号がローの場合、電力変換器２０を停止状態に維持する待機信号、ステップＢ３６で出力された信号がハイの場合、電力変換器２０がスイッチング動作を再開する再起動を意味する信号である。これによって、自変換所と直流系統３とが少なくとも１つの有効な送電経路を形成するように接続されており、かつ直流側に流れる電流が概略ゼロとなっている場合に、電力変換器２０のスイッチング動作を再開するための再起動許可信号Ｘ９が出力される。 The restart signal is a standby signal that keeps the power converter 20 in the stopped state when the signal output in step B36 is low, and the power converter 20 performs a switching operation when the signal output in step B36 is high. It is a signal that means restarting to restart. As a result, when the self-converter and the DC system 3 are connected so as to form at least one effective transmission path, and the current flowing on the DC side is approximately zero, the power converter 20 A restart permission signal X9 for restarting the switching operation is output.
　再起動許可信号Ｘ９がハイになると、ゲートブロック中の電力変換器２０のスイッチング素子のスイッチング動作が再開される。上記の一連の処理は自変換所の情報のみで行われるため、他変換所の情報は必要とされず、通信に関わる遅延や通信に関わる信号処理の遅延が生じない。したがって、制御装置１００は、直流事故等によって電力変換器２０が停止した場合にも迅速に電力変換器２０を再起動させることができる。 When the restart permission signal X9 becomes high, the switching operation of the switching element of the power converter 20 in the gate block is restarted. Since the above series of processing is performed only with the information of the own conversion station, the information of the other conversion station is not required, and the delay related to communication and the delay of signal processing related to communication do not occur. Therefore, the control device 100 can quickly restart the power converter 20 even when the power converter 20 is stopped due to a DC accident or the like.
　このように、制御装置１００が、電力変換器２０がゲートブロックしている場合に、電力変換器２０の直流側に電流が流れておらず、且つ直流遮断器２１０のうちいずれかの直流遮断器２１０が閉状態である場合に、電力変換器２０が運転を再開するようにゲートブロックを解除することにより、迅速に電力変換器２０を再起動させることができる。 In this way, when the power converter 20 is gate-blocked in the control device 100, no current is flowing to the DC side of the power converter 20, and any of the DC breakers 210 is a DC breaker. When the 210 is in the closed state, the power converter 20 can be quickly restarted by releasing the gate block so that the power converter 20 resumes operation.
　以上説明した第１実施形態によれば、制御装置１００が、送電システムの状況に応じて、種々の処理を行うことにより、電力変換器２０をより適切に制御することができる。
　より具体的には、送電システムが非定常状態の場合における運転継続性能を向上した電力変換装置を提供することができる。 According to the first embodiment described above, the control device 100 can control the power converter 20 more appropriately by performing various processes according to the situation of the power transmission system.
More specifically, it is possible to provide a power conversion device having improved operation continuation performance when the power transmission system is in an unsteady state.
　（第２実施形態）
　以下、第２実施形態について説明する。第２実施形態では、電力変換器２０の機能構成が、第１実施形態の電力変換器２０の構成と異なる。以下、第１実施形態との相違点について説明する。 (Second Embodiment)
Hereinafter, the second embodiment will be described. In the second embodiment, the functional configuration of the power converter 20 is different from the configuration of the power converter 20 of the first embodiment. Hereinafter, the differences from the first embodiment will be described.
　図１１は、第２実施形態の電力変換装置１０の構成の一例を示す図である。電力変換器２０は、各正側アーム４０Ｐ（４０Ｐ－１Ａから４０Ｐ－３Ａ）、および各負側アーム４０Ｎ（４０Ｎ－１Ａから４０Ｐ－３Ａ）のそれぞれには少なくとも１つのスイッチング素子（４１Ｐ－１～４１Ｐ－３、４１Ｎ－１～４１Ｎ－３）が直列に接続されている。スイッチング素子のそれぞれに対して、帰還ダイオード４２（４２Ｐ－１～４２Ｐ－３、４２Ｎ－１～４２Ｎ－３）が逆並列に接続されている。正側アーム４０Ｐと負側アーム４０Ｎの接点に端子ＮＡＣが位置する。変圧器ＴＲの二次巻線と端子ＮＡＣの間に交流インピーダンスＬＡＣが介在し、電流センサＣＴは交流インピーダンスＬＡＣを流れる電流を検出するように設置される。交流インピーダンスＬＡＣはリアクトルにより形成される場合や変圧器ＴＲの漏れインピーダンス成分により形成される場合がある。 FIG. 11 is a diagram showing an example of the configuration of the power conversion device 10 of the second embodiment. The power converter 20 has at least one switching element (41P-1 to 40P-3A) for each of the positive arm 40P (40P-1A to 40P-3A) and each negative arm 40N (40N-1A to 40P-3A). 41P-3, 41N-1 to 41N-3) are connected in series. Feedback diodes 42 (42P-1 to 42P-3, 42N-1 to 42N-3) are connected in antiparallel to each of the switching elements. The terminal NAC is located at the contact point between the positive arm 40P and the negative arm 40N. An AC impedance LAC is interposed between the secondary winding of the transformer TR and the terminal NAC, and the current sensor CT is installed so as to detect the current flowing through the AC impedance LAC. The AC impedance LAC may be formed by a reactor or a leakage impedance component of a transformer TR.
　電力変換器２０のエネルギー蓄積要素は端子ＮＤＣＰと端子ＮＤＣＮの間に接続される直流コンデンサＣＤＣである。直流コンデンサＣＤＣは少なくとも１つ以上の直列接続構成である。複数の直流コンデンサが直列に接続される場合には、中性点を端子ＮＤＣＭとする。電圧センサ４６Ｐは、端子ＮＤＣＰと端子ＮＤＣＭの電圧を検出するように設けられ、電圧センサ４６Ｎは、端子ＮＤＣＭと端子ＮＤＣＮの電圧を検出するように設けられている。直流コンデンサＣＤＣが一つのみの場合には、電圧センサ４６は、端子ＮＤＣＰと端子ＮＤＣＮの間に一つ設置される。 The energy storage element of the power converter 20 is a DC capacitor CDC connected between the terminal NDCP and the terminal NDCN. The DC capacitor CDC has at least one or more series connection configurations. When a plurality of DC capacitors are connected in series, the neutral point is the terminal NDCM. The voltage sensor 46P is provided so as to detect the voltage of the terminal NDCP and the terminal NDCM, and the voltage sensor 46N is provided so as to detect the voltage of the terminal NDCM and the terminal NDCN. When there is only one DC capacitor CDC, one voltage sensor 46 is installed between the terminal NDCP and the terminal NDCN.
　上記のような２レベルインバーター回路において、第１実施形態で説明した処理が適用されてもよい。 The process described in the first embodiment may be applied to the two-level inverter circuit as described above.
　以上説明した第２実施形態によれば、第１実施形態の電力変換装置１０が奏する効果と同様の効果を奏する。 According to the second embodiment described above, the same effect as that of the power conversion device 10 of the first embodiment is obtained.
　また、上記の各実施形態では、制御装置１００が、電力変換器２０に含まれるコンデンサの電圧に基づいて、負荷装置８０に電力を消費または蓄電させるように負荷装置８０を制御するものとしたが、これに代えて、制御装置１００は、電力変換器２０の交流側の有効電力と直流側の電力との差異が規定範囲を逸脱する場合に負荷装置８０に電力を消費または蓄電させる制御を行ってもよい。これにより、過電圧が抑制される。 Further, in each of the above embodiments, the control device 100 controls the load device 80 so that the load device 80 consumes or stores electric power based on the voltage of the capacitor included in the power converter 20. Instead of this, the control device 100 controls the load device 80 to consume or store power when the difference between the active power on the AC side and the power on the DC side of the power converter 20 deviates from the specified range. You may. As a result, overvoltage is suppressed.
　本発明のいくつかの実施形態を説明したが、これらの実施形態は、例として提示したものであり、発明の範囲を限定することは意図していない。これら実施形態は、その他の様々な形態で実施されることが可能であり、発明の要旨を逸脱しない範囲で、種々の省略、置き換え、変更を行うことができる。これら実施形態やその変形は、発明の範囲や要旨に含まれると同様に、特許請求の範囲に記載された発明とその均等の範囲に含まれるものである。 Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention as well as in the scope of the invention described in the claims and the equivalent scope thereof.

Claims (10)

  1. 　少なくとも３つのレグを含み、
    　前記レグのそれぞれは、
    　一以上のセルを含むアームと、
    　前記アームの交流側に接続されたインダクタンスと、
    　前記インダクタンスに流れる電流を検出する電流検出部と、を含み、
    　前記３つのレグのうち、第１レグはＵ相、第２レグはＶ相、第３レグはＷ相に接続され、
    　前記セルは、
    　スイッチング素子と、
    　コンデンサと、
    　前記コンデンサの両端の電圧を検出する電圧検出部と、
    　制御部により出力された制御信号に基づいて前記スイッチング素子を制御して直流側に出力する電力を制御し、前記電圧検出部により検出された前記コンデンサの電圧を前記制御部に提供するセル制御部と、を含み、
    　交流電力を直流電力または直流電力を交流電力に変換する変換器と、
    　前記変換器の直流側における正極線と負極線または接地線との間に接続される負荷装置と、
    　前記変換器に含まれる前記電圧検出部により検出されたコンデンサの電圧に基づいて、前記負荷装置に電力を消費または蓄電させるように前記負荷装置を制御する前記制御部と、を備える
    　電力変換装置。     Includes at least 3 legs
    Each of the legs
    With an arm containing one or more cells,
    With the inductance connected to the AC side of the arm,
    Includes a current detector that detects the current flowing through the inductance.
    Of the three legs, the first leg is connected to the U phase, the second leg is connected to the V phase, and the third leg is connected to the W phase.
    The cell is
    Switching element and
    With a capacitor
    A voltage detector that detects the voltage across the capacitor and
    A cell control unit that controls the switching element based on a control signal output by the control unit to control the power output to the DC side, and provides the voltage of the capacitor detected by the voltage detection unit to the control unit. And, including
    A converter that converts AC power to DC power or DC power to AC power,
    A load device connected between the positive electrode wire and the negative electrode wire or the ground wire on the DC side of the converter.
    A power converter including a control unit that controls the load device so that the load device consumes or stores electric power based on the voltage of a capacitor detected by the voltage detection unit included in the converter.
  2. 　前記制御部は、
    　前記コンデンサの電圧が第１閾値を超えた場合に、前記負荷装置に電力を消費または蓄電させるように前記負荷装置を制御し
    　前記コンデンサの電圧が第２閾値以下になった場合に、前記負荷装置に電力を消費または蓄電させるように前記負荷装置を制御することを停止する、
    　請求項１に記載の電力変換装置。     The control unit
    When the voltage of the capacitor exceeds the first threshold value, the load device is controlled so that the load device consumes or stores electric power, and when the voltage of the capacitor becomes equal to or lower than the second threshold value, the load device is used. Stops controlling the load device to consume or store power in the
    The power conversion device according to claim 1.
  3. 　前記第１閾値は、過電圧が生じている状況に応じた電圧であり、
    　前記第２閾値は、前記第１閾値よりも小さい定格レベル以下の電圧である、
    　請求項２に記載の電力変換装置。     The first threshold value is a voltage according to the situation where an overvoltage is occurring.
    The second threshold value is a voltage equal to or lower than the rated level smaller than the first threshold value.
    The power conversion device according to claim 2.
  4. 　前記制御部は、
    　直流側の系統で事故が発生したことを示す信号を取得していない場合、前記直流側に流れる直流電流と、コンデンサの電圧を検出する電圧検出部により検出されたコンデンサの電圧とに基づく制御値に基づいて、前記変換器を制御するための制御信号を生成し、
    　前記直流側の系統で事故が発生したことを示す信号を取得した場合、前記直流側に流れる直流電流と前記電圧検出部により検出されたコンデンサの電圧とに基づく制御値を制限した制限制御値に基づいて、前記制御信号を生成する、
    　請求項１から３のうちいずれか１項に記載の電力変換装置。     The control unit
    When a signal indicating that an accident has occurred in the system on the DC side has not been acquired, a control value based on the DC current flowing on the DC side and the voltage of the capacitor detected by the voltage detector that detects the voltage of the capacitor. A control signal for controlling the converter is generated based on
    When a signal indicating that an accident has occurred in the system on the DC side is acquired, the control value is limited to a control value based on the DC current flowing on the DC side and the voltage of the capacitor detected by the voltage detection unit. Based on this, the control signal is generated.
    The power conversion device according to any one of claims 1 to 3.
  5. 　前記直流側と前記直流側に接続された直流送電路との接点のうち少なくとも１つには直流遮断器が接続され、
    　前記制御部は、前記直流遮断器の開閉状態を制御可能である、
    　請求項１から４のうちいずれか１項に記載の電力変換装置。     A DC circuit breaker is connected to at least one of the contacts between the DC side and the DC transmission line connected to the DC side.
    The control unit can control the open / closed state of the DC circuit breaker.
    The power conversion device according to any one of claims 1 to 4.
  6. 　前記制御部は、前記変換器がゲートブロックしている場合に、前記変換器の直流側に電流が流れておらず、且つ前記直流遮断器のうちいずれかの前記直流遮断器が閉状態である場合に、前記変換器が運転を再開するように前記ゲートブロックを解除する、
    　請求項５に記載の電力変換装置。     In the control unit, when the converter is gate-blocked, no current is flowing to the DC side of the converter, and one of the DC circuit breakers is in a closed state. In the case, the gate block is released so that the converter resumes operation.
    The power conversion device according to claim 5.
  7. 　前記制御部は、
    　直流側の電流変化率が規定値よりも大きい場合に、前記直流側が事故状態であることを検知し、
    　前記直流側の電流変化率が前記規定値以下になった場合に直流側が事故状態でなくなったことを検知し、
    　前記事故状態の検知結果に基づいて、前記変換器を制御する、
    　請求項５または６に記載の電力変換装置。     The control unit
    When the current change rate on the DC side is larger than the specified value, it is detected that the DC side is in an accident state, and
    When the current change rate on the DC side becomes equal to or less than the specified value, it is detected that the DC side is no longer in an accident state.
    The converter is controlled based on the detection result of the accident state.
    The power conversion device according to claim 5 or 6.
  8. 　前記アームは、複数のセルを直列接続して構成され、前記セルはハーフブリッジ回路、もしくはフルブリッジ回路であり、
    　前記インダクタンスは、前記アームに直列接続されるバッファリアクトルであり、
    　前記コンデンサは、各セルが有するセルコンデンサである、
    　請求項１から７のうちいずれかの１項に記載の電力変換装置。     The arm is configured by connecting a plurality of cells in series, and the cell is a half-bridge circuit or a full-bridge circuit.
    The inductance is a buffer reactor connected in series with the arm.
    The capacitor is a cell capacitor of each cell.
    The power conversion device according to any one of claims 1 to 7.
  9. 　少なくとも３つのレグを含み、
    　前記レグのそれぞれは、
    　一以上のアームと、
    　前記アームと並列に１つもしくは、２つ以上直列接続される直流コンデンサと、
    　前記直流コンデンサの両端の電圧を検出する電圧検出部と、
    　前記アームの交流側に接続されたインダクタンスと、
    　前記インダクタンスに流れる電流を検出する電流検出部と、を含み、
    　前記３つのレグのうち、第１レグはＵ相、第２レグはＶ相、第３レグはＷ相に接続され、
    　前記アームは、１つのスイッチング素子または、２つ以上のスイッチング素子を直列接続して構成され、
    　交流電力を直流電力または直流電力を交流電力に変換する変換器と、
    　前記変換器の直流側における正極線と負極線または接地線との間に接続される負荷装置と、
    　前記変換器に含まれる前記電圧検出部により検出された前記直流コンデンサの電圧に基づいて、前記負荷装置に電力を消費または蓄電させるように前記負荷装置を制御する制御部と、を備える、
    　電力変換装置。     Includes at least 3 legs
    Each of the legs
    With one or more arms
    A DC capacitor connected in parallel with the arm, or two or more in series,
    A voltage detector that detects the voltage across the DC capacitor and
    With the inductance connected to the AC side of the arm,
    Includes a current detector that detects the current flowing through the inductance.
    Of the three legs, the first leg is connected to the U phase, the second leg is connected to the V phase, and the third leg is connected to the W phase.
    The arm is configured by connecting one switching element or two or more switching elements in series.
    A converter that converts AC power to DC power or DC power to AC power,
    A load device connected between the positive electrode wire and the negative electrode wire or the ground wire on the DC side of the converter.
    A control unit that controls the load device so as to consume or store electric power in the load device based on the voltage of the DC capacitor detected by the voltage detection unit included in the converter.
    Power converter.
  10. 　前記変換器の交流側は交流電気設備に接続され、
    　前記交流電気設備は、風力発電所もしくは、交流系統である、
    　請求項１から９のうちいずれか１項に記載の電力変換装置。     The AC side of the converter is connected to AC electrical equipment and
    The AC electrical equipment is a wind power plant or an AC system.
    The power conversion device according to any one of claims 1 to 9.
PCT/JP2019/021681 2019-05-31 2019-05-31 Power conversion device WO2020240810A1 (en)

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