JP3164678B2 - Inverter control device for grid interconnection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control device for interconnecting an AC system and transferring power to and from the AC system. Even when the connection to the AC system is interrupted, the inverter alone supplies the load to the load. The present invention relates to a control device of a grid interconnection inverter for continuously supplying power.

[0002]

2. Description of the Related Art A system for supplying power of a DC power supply such as a fuel cell or a secondary battery or a DC power supply such as a rectifier to a load, or transferring power between the DC power supply and an AC system. An interconnection inverter is used.

FIG. 6 is a diagram showing an example of this type of conventional control device for a grid-connected inverter, which comprises a voltage-type self-excited inverter 10 and an inverter control device 100. The voltage-type self-excited inverter 10 includes an inverter main circuit 1, a DC capacitor 2, and a transformer 3, which will be described later. The inverter main circuit 1 includes power conversion elements (controllable rectifying elements) GU, GV, GW, GX, GY. , GZ and rectifying elements DU, DV, DW, DX, DY, DZ. As the power conversion elements GU, GV, GW, GX, GY, GZ, self-extinguishing ability of GTO (gate turn-off thyristor), power transistor, IGBT (insulated gate bipolar transistor), SI (static induction type) thyristor, etc. A power conversion element having a characteristic is used. The voltage-type self-excited inverter 10 is connected to the three-phase AC system 6 via the interconnection breaker 5 and is connected to the load 7.

[0004] The inverter control device 100 includes an active / reactive current reference generator 101, a phase detector 103, an active / reactive current detector 104, a current control circuit 105, a gate control circuit 106, or hall CTs 201 and 202. It is configured.

[0005] The inverter main circuit 1 includes power conversion elements G
By changing the energization periods of U, GV, GW, GX, GY, and GZ, the three-phase output voltages of the inverter main circuit 1 can be controlled. The phases and amplitudes of the three-phase output voltages of the inverter main circuit 1 are determined by the system voltage VR of the AC system 6,
By adjusting according to the phase and amplitude of VS and VT,
A current transmitted to and received from the AC system 6 via the impedance of the transformer 3 is controlled.

[0006] By this current control, the inverter 10
The DC power of the DC voltage source 4 is converted into active power, or the active power is converted into DC power. The active power is exchanged with the AC system 6 via the interconnection breaker 5, and the reactive power is supplied. Similarly, the inverter 10 also supplies active power and reactive power to the load 7. The current control of the inverter 10 is performed by the inverter control device 100 as follows. The phase detection circuit 103 is connected to the system voltages VR and V of the three-phase AC system 6.
The system voltage phase θ of S and VT is detected on the inverter 10 side of the interconnection breaker 5.

The active / reactive current detector 104 has a Hall CT2
Inverter output AC current i detected at 01 and 202
An active current component and a reactive current component are detected from R and iT as an active current detection value iq and a reactive current detection value id, respectively.

[0008] The current control circuit 105 is configured to detect the active current detection value iq from the active / reactive current detector 104 and the reactive current detection value i.
The inverter output voltage references VRc, VSc, which determine the three-phase output voltages of the inverter main circuit 1 such that d becomes equal to the active current reference value iqc from the active / reactive current reference generator 101 and the reactive current reference value idc. Calculate VTc. This inverter output voltage reference VRc, VSc, VT
In the calculation of c, the system voltages VR, VS, VT of the AC system 6 are calculated.
In order to determine the inverter output voltage phase with respect to this phase, the system voltage phase θ detected by the phase detector 103 is used.

The gate control circuit 106 controls the inverter output voltage references VRc, VSc, VTc and the gate control circuit 106.
The power conversion elements GU, GV, GW, G constituting the inverter main circuit 1 are compared with the internally generated triangular wave carrier signal.
A gate signal for determining the energizing periods of X, GY, and GZ is output.

Since the details of the operation of the system interconnection inverter and the control device thereof shown in FIG. 6 described above are described in the following documents, the description is omitted here.

Reference: Shun-ichi Hirose et al “Applic
ation of a digital instantaneouscurrent control fo
r static induction thyristor converters in the uti
lity line ”, PCIM Proceeding, pp343-349, Dec.8,1988
An example is disclosed in in Japan. Also, the gate control circuit 106
For the operation of

Literature: The Institute of Electrical Engineers of Japan, "Semiconductor Power Conversion Circuit" edited by the Technical Committee on Semiconductor Power Conversion Methods, page 108 to page 1
12. The Institute of Electrical Engineers of Japan, P on March 31, 1987
It is disclosed as WM control.

[0013]

The conventional control device for a grid connection inverter shown in FIG. 6 has the following disadvantages.
That is, when a fault or the like occurs in the AC system 6 and the interconnection breaker 5 is opened, the inverter 10 cannot exchange power with the AC system 6 and cannot detect the phase of the AC voltage of the AC system 6. The active current component iq and the reactive current component id detected from the inverter output AC currents iR and iT cannot be output according to the active current reference value iqc and the reactive current reference value idc from the valid reactive current reference generator 101. As a result, the output voltage and the frequency of the inverter 10 increase or decrease and the power cannot be properly supplied to the load 7.
There is a problem that has to stop driving.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and when the inverter is connected to the AC system to exchange power with the AC system, the connection to the AC system is interrupted. It is an object of the present invention to provide a control device for a grid interconnection inverter that can continuously supply power to a load even when the inverter is used.

[0015]

According to a first aspect of the present invention, an AC voltage is supplied to a load from an AC system via a connection breaker, and the AC system is connected to the AC system. In a system interconnection inverter that is interconnected and converts DC power from a DC power supply into AC power and transfers active power or reactive power to the load and the AC system,
Active / reactive current reference generating means for generating an active current reference signal and a reactive current reference signal; and active / reactive current detection means for outputting the active current component and the reactive current component of the output current of the inverter as a valid current signal and a reactive current signal, respectively. And phase detection means for detecting the phase of the AC voltage and outputting it as a phase signal, and controlling the active current signal to be equal to the active current reference signal and controlling the reactive current signal to be equal to the reactive current reference signal. Current control means for outputting the output voltage reference signal of the inverter, gate control means for controlling the output voltage of the inverter based on the reference signal of the inverter output and the phase signal, and detecting the frequency of the AC voltage Frequency detection means for outputting as a signal, and detecting the amplitude of the AC voltage and outputting the voltage as a voltage amplitude signal Voltage amplitude detection means, frequency reference generation means for outputting a frequency reference signal, voltage amplitude reference generation means for outputting a voltage amplitude reference signal, and a frequency correction signal calculated from a deviation between the frequency reference signal and the frequency signal. Frequency correction calculating means for calculating, a voltage amplitude correction calculating means for calculating a voltage amplitude correction signal from a deviation between the voltage amplitude reference signal and the voltage amplitude signal, and adding the effective current reference signal and the voltage amplitude correction signal. An output means for outputting to the current control means as an effective current correction reference signal, and adding the reactive current reference signal and the frequency correction signal to output the reactive current correction reference signal to the current control means. is there.

[0016]

According to the invention corresponding to claim 1, the current control means controls the active current signal to be equal to the active current correction reference signal and controls the reactive current signal to be equal to the reactive current correction reference signal. By outputting the output voltage reference signal of the inverter, the inverter alone can continue to supply power to the load even when the connection to the AC system is interrupted.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. 6 is different from the conventional example of FIG. 6 in that a frequency detector 107 forming the frequency detecting means, a voltage amplitude detector 108 forming the voltage detecting means, an adding circuit 110 forming the adding means, and a voltage forming the voltage amplitude detecting means An amplitude reference generator 121, a frequency reference generator 122 forming frequency reference generating means, a frequency correction calculating circuit 131 forming frequency correction calculating means, and a voltage amplitude correcting calculating circuit 132 forming voltage amplitude correcting calculating means are added. And
The other points are the same as those in FIG.

The frequency detector 107 detects the frequency of the AC voltage applied from the AC system 6 or the inverter 10 to the load 7 and detects the frequency signal F. Voltage amplitude detector 1
08 detects the amplitude of the AC voltage and outputs it as a voltage amplitude signal V. Frequency reference generator 122 outputs frequency reference signal Fc. Voltage amplitude reference generator 121 outputs voltage amplitude reference signal Vc. Frequency correction operation circuit 131
Are the frequency reference signal Fc and the frequency signal F
The frequency correction signal EF is output from the deviation from the above. The voltage amplitude correction operation circuit 132 outputs a voltage amplitude correction signal EV from a deviation between the voltage amplitude reference signal Vc and the voltage amplitude signal V.

The adder circuit 110 has an adder 111 and an adder 112. The adder 111 converts the active current reference iqc output from the active / reactive current reference generator 101 into a voltage output from the voltage amplitude correction operation circuit 132. Amplitude correction signal EV
And an effective current correction reference signal iqm is subtracted from the current control circuit 1
05, and the adder 112 outputs the frequency correction signal EF output from the frequency correction operation circuit 131 from the reactive current reference idc output from the active / reactive current reference generator 101.
And the reactive current correction reference signal idm is subtracted from the current control circuit 1
Output to 05.

FIG. 2 shows the frequency correction operation circuit 131 of FIG.
Shows a specific circuit example of the adder 1311.
And a proportional integral operation circuit 1312. The proportional integral operation circuit 1312 includes an operational amplifier A and resistors R1, R2, R
3 and a capacitor C.

FIG. 3 shows the voltage amplitude correction operation circuit 13 shown in FIG.
2 shows a specific circuit example, which is an adder 1321.
And a proportional integral operation circuit 1322. The proportional integral operation circuit 1322 includes an operational amplifier A and resistors R1, R2, R
3 and a capacitor C.

With such a configuration, the current control circuit 10
5 to control the effective current signal input to the control signal 5 to be equal to the effective current correction reference signal, and to control the reactive current signal to be equal to the reactive current correction reference signal idm to output the output voltage reference signal of the inverter. Can,
Thus, even when the connection to the AC system is interrupted, power can be continuously supplied to the load 7 by the inverter alone.

Hereinafter, the operation of this embodiment will be described.
In FIG. 1, a frequency detector 107 detects the frequency of the AC voltage on the inverter 10 side of the interconnection breaker 5 and outputs a frequency signal F. The voltage amplitude detector 108 detects the amplitude of the AC voltage on the inverter 10 side of the interconnection breaker 5 and outputs a voltage amplitude signal V. The frequency reference generator 122 is connected to the AC system 6
And outputs a frequency reference signal Fc corresponding to the rated frequency of the voltage. Voltage amplitude reference generator 121 outputs a voltage amplitude reference signal Vc corresponding to the rated amplitude of the voltage of AC system 6.

The frequency correction operation circuit 131 is connected to the frequency reference signal Fc from the frequency reference generator 122 and the frequency detector 1
07 is input to the adder 131 shown in FIG.
After taking the difference by 1, a frequency correction signal EF is output via the proportional-integral operation circuit 1312.

The voltage amplitude correction operation circuit 132 receives the voltage reference signal Vc from the voltage amplitude reference generator 121 and the voltage amplitude signal V from the voltage amplitude detector 108, and calculates the difference with the adder 1321 in FIG. , And outputs a voltage amplitude correction signal EV via a proportional-integral operation circuit 1322.

The adder circuit 110 outputs the reactive current reference idc output from the active / reactive current reference generator 101 by the adder 112.
Is subtracted from the frequency correction signal EF output from the frequency correction operation circuit 131 to output a reactive current correction reference signal idm.
The voltage amplitude correction signal EV output from the voltage amplitude correction operation circuit 132 is subtracted from the effective current reference iqc output from the above-mentioned circuit to output an effective current correction reference signal iqm.

The current control circuit 105 includes an adder circuit 110 instead of the reactive current reference idc input in the conventional example of FIG.
Of the reactive current correction reference signal idm, which is the output of the prior art, and the effective current reference iqc input in the conventional example of FIG.
Instead, the active current correction reference signal iqm output from the adding circuit 110 is input, and the active current detection value iq and the reactive current detection value id from the active / reactive current detector 104 are used as the active current correction reference signal iqm and the reactive current correction. Inverter output voltage references VRc, VSc, VT for determining three-phase output voltages of inverter main circuit 1 so as to be equal to reference signal idm.
Calculate c.

In the embodiment shown in FIG. 1, when the interconnection breaker 5 is closed and the inverter 10 is connected to the AC system 6, the frequency detector 107 detects the frequency of the AC voltage of the AC system 6 as a frequency signal F. Since the voltage amplitude detector 108 detects the amplitude of the AC voltage of the AC system as the voltage amplitude signal V, the frequency signal F and the frequency reference signal Fc are equal, and the voltage amplitude signal V and the voltage reference signal Vc are equal. I have.

As a result, the frequency correction signal EF output from the frequency correction operation circuit 131 and the voltage amplitude correction operation circuit 1
32, the voltage amplitude correction signal EV output becomes zero, and the active current correction reference signal iqm and the reactive current correction reference signal idm
Are equal to the active current reference iqc and the reactive current reference idc, respectively. Therefore, the inverter 10 converts the active current and the reactive current according to the active current reference signal iqc and the reactive current reference signal idc from the active reactive current reference generator 101 into the AC system and the Supply to the load.

On the other hand, the interconnection breaker 5 opens and the inverter 10
Is supplying power to the load 7 alone, the frequency signal F detected by the frequency detector 107 is different from the frequency of the AC voltage of the AC system 6, and the voltage amplitude signal V detected by the voltage Since the amplitude is different from the amplitude of the AC voltage of the system 6, there is a difference between the frequency signal F and the frequency reference signal Fc, and also a difference between the voltage amplitude signal V and the voltage reference signal Vc. Thereby, the frequency correction operation circuit 131
And the voltage amplitude correction signal EV output from the voltage amplitude correction operation circuit 132 are not zero.

The adding circuit 110 corrects the reactive current reference idc and the active current reference iqc with the frequency correction signal EF and the voltage amplitude correction signal EV, respectively, and converts the reactive current correction reference signal idm and the active current correction reference signal iqm into the current control circuit 105. Output to

The inverter 10 supplies the active current and the reactive current to the load in accordance with the active current reference signal iqm and the reactive current reference signal idm from the adder circuit 110, thereby changing the frequency and amplitude of the inverter output voltage to the frequency reference signal Fc and the voltage. It is made equal to the amplitude reference Vc.

In this embodiment, even when the interconnection breaker 5 is closed and the inverter 10 and the AC system 6 are interconnected, the interconnection breaker 5 is opened and the inverter 10 supplies power to the load independently. At the same time, the same control circuit can be used, and it is possible to reduce the fluctuation that occurs when the inverter 10 switches from the interconnected operation to the isolated operation or vice versa.

Hereinafter, the detailed operation will be described with reference to FIGS. FIG. 4 is a representation of FIG. 1 in a single-line connection diagram, and illustrates the movement of various main circuit quantities when the inverter is switched from interconnected operation to isolated operation. FIG. 5 is a vector diagram illustrating a change in load voltage when the inverter switches from the interconnected operation to the isolated operation.

In FIG. 4, the inverter output current output from the inverter 10 is Ic, the load current flowing through the load is Is,
The system current flowing to the AC system 6 via the interconnection breaker 5 is represented by I
g, the load voltage generated by the load 7 is Vs, and the AC system 6
Are shown as Vg, and the load impedance is shown as Z. For simplicity, the AC system 6 is an infinite bus. The inverter 10 outputs an inverter output current Ic equal to the current reference of the inverter control device 100.

First, the interconnection breaker 5 is closed and the inverter 1
Consider a state in which 0 is performing grid-connected operation. AC system 6
Indicates that the system voltage Vg maintains the rated voltage amplitude and the rated frequency regardless of the current transmitted to and received from the inverter.
Since the inverter 10 and the load 7 are connected to the AC system 6 via the interconnection breaker 5, the load voltage Vs is equal to the system voltage Vg.
And the same rated voltage amplitude and rated frequency. The following equation (1) holds for the load voltage Vs and the system voltage Vg. Vs = Vg (1) Further, the following equation (2) holds for the inverter output current Ic, the load current Is, and the system current Ig. Ic = Is + Ig (2) Furthermore, the load voltage Vs and the load current Is are as follows.
Equation (3) holds. Vs = Z · Is (3)

Next, when the circuit breaker 5 is opened and the inverter 10 is operated independently, the current Ig flowing to the AC system 6 during the interconnection operation flows to the load 7 unless the inverter control device 100 changes the current reference value. Will be. Assuming that the load voltage at this time is Vs1, the following equation (4) is established. Vs1 = Z · Ic = Z · (Is + Ig) = Vg + Z · Ig (4) That is, the voltage of Z · Ig is added to the load 7 to the rated voltage Vg of the AC system 6. FIG. 5 is a diagram for explaining this state using a vector.

In FIG. 5, a vector is drawn on orthogonal dq coordinates, and the system voltage Vg is taken on the q axis. At the time of the interconnection operation, the system voltage Vg and the load voltage Vs are equally on the q-axis. However, in the case of the isolated operation, the current Ig flowing in the AC system 6 at the time of the interconnection flows to the load 7, so that the load voltage Vs is To Vs1 according to the impedance Z of. Next, the inverter 10 further changes the load voltage in order to flow Ic to Vs1 in accordance with the current reference value. This indicates that when the inverter 10 switches from the interconnection operation to the isolated operation, the amplitude and frequency of the load voltage change unless the inverter control device 100 changes the current reference value. That is, the AC system 6
The d-axis component of the voltage component that changes due to the current Ig flowing through
The axis component changes the amplitude.

As described above, when the inverter 10 shifts from the interconnection operation to the isolated operation, the effective current reference value Iqc of the current reference value Ic is corrected by the deviation between the AC system voltage rated amplitude and the AC voltage amplitude, and is invalidated. By correcting the current reference value Idc by the deviation between the AC system voltage rated frequency and the AC voltage frequency, the inverter can control the output voltage to be equal to the rated amplitude and the rated frequency of the AC system voltage.

In the embodiment shown in FIG. 1, the addition circuit 110, the frequency correction operation circuit 131, and the voltage amplitude correction operation circuit 132 are realized by electronic circuits. However, they can be realized by software using a microcomputer or the like. Can also. In this case, if the current control circuit 105 and the active / reactive current detector 104 are realized by microcomputer software in the conventional example of FIG. 6, the addition circuit 110, the frequency correction operation circuit 131, and the voltage amplitude correction operation circuit 132
By adding this function as software, there is an advantage that the present invention can be easily incorporated into a conventional control device.

[0041]

According to the present invention, regardless of whether the interconnection state between the system interconnection inverter and the AC system changes from the interconnection state to the independent state, or conversely, from the independent state to the interconnection state, The appropriate power can be supplied to the load from the power generation system using the grid connection inverter without capturing the change as a state signal of the grid connection breaker and without temporarily stopping the operation of the grid connection inverter. In addition, it is possible to provide a control device for a grid-connection inverter that can enhance the reliability of a power generation system using the grid-connection inverter and expand its application range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a control device for a grid interconnection inverter according to the present invention.

FIG. 2 is a diagram showing a specific circuit example of the frequency correction operation circuit of FIG. 1;

FIG. 3 is a diagram showing a specific circuit example of a voltage amplitude correction operation circuit in FIG. 1;

FIG. 4 is a diagram for explaining movements of various main circuit amounts when the inverter of FIG. 1 switches from interconnected operation to isolated operation.

FIG. 5 is a diagram for explaining a vector diagram for explaining a change in load voltage when the inverter of FIG. 1 switches from interconnected operation to isolated operation.

FIG. 6 is a diagram for explaining a conventional system interconnection inverter and its control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Inverter main circuit, 2 ... DC capacitor, 3 ... Transformer, 4 ... DC voltage source, 5 ... Interconnection breaker, 6 ... AC system,
7 ... Load, 10 ... Inverter, 100 ... Inverter control device, 101 ... Effective reactive current reference generator, 103 ... Phase detection circuit, 104 ... Effective reactive current detector, 105 ... Current control circuit, 106 ... Gate control circuit, 201 , 202 ...
Hall CT, GU, GV, GW, GX, GY, GZ ... power conversion element (controllable rectifier), DU, DV, DW, D
X, DY, DZ: rectifier, 107: frequency detector, 1
08: voltage amplitude detector, 110: addition circuit, 121: voltage amplitude reference generator, 122: frequency reference generator, 131
... frequency correction operation circuit, 132 ... voltage amplitude correction operation circuit, 111, 112 ... adder, 1311, 1321 ... adder, 1312, 1322 ... proportional integration operation circuit, A ... operation amplifier, R1, R2, R3 ... resistance, C: Capacitor.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kimito Oyama 2-2-230 Kanda Jimbocho, Chiyoda-ku, Tokyo Tokyo Electric Power Company R & D Laboratory (72) Inventor Shunichi Hirose 1 Toshiba-cho, Fuchu-shi, Tokyo Stock (72) Inventor Tatsuro Yamaguchi 1 Toshiba-cho, Fuchu-shi, Tokyo In-house Toshiba Fuchu Factory (72) Inventor Susumu Tanaka 1-1-1, Shibaura, Minato-ku, Tokyo Toshiba Corporation In the head office (56) References JP-A-3-196207 (JP, A) JP-A-61-164433 (JP, A) JP-A-4-79728 (JP, A) JP-A-3-27730 (JP, A) A) JP-A-59-153426 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 9/06 504 H02J 3/00-5/00

Claims (1)

(57) [Claims] An AC voltage is supplied from an AC system to a load via a connection circuit breaker. The load is connected to the AC system, converts DC power from a DC power supply into AC power, and converts the DC power into AC power. An active / reactive current reference generating means for generating an active current reference signal and a reactive current reference signal in a grid interconnection inverter for transmitting and receiving active power or reactive power to and from the grid; and an active current component and a reactive current component of an output current of the inverter. And active current detection means for outputting the effective current signal and the reactive current signal, respectively, phase detection means for detecting the phase of the AC voltage and outputting it as a phase signal, and making the effective current signal equal to the effective current reference signal. Control to make the reactive current signal equal to the reactive current reference signal to output the output voltage reference signal of the inverter. Control means, gate control means for controlling the output voltage of the inverter based on the reference signal and the phase signal of the inverter output, frequency detection means for detecting the frequency of the AC voltage and outputting it as a frequency signal, Voltage amplitude detecting means for detecting an amplitude and outputting as a voltage amplitude signal; frequency reference generating means for outputting a frequency reference signal; voltage amplitude reference generating means for outputting a voltage amplitude reference signal; the frequency reference signal and the frequency signal Frequency correction calculating means for calculating a frequency correction signal from the deviation of the voltage amplitude reference signal, and a voltage amplitude correction calculation means for calculating a voltage amplitude correction signal from the deviation between the voltage amplitude signal, the effective current reference signal, Adding the voltage amplitude correction signal and outputting the same as an effective current correction reference signal to the current control means; Current reference signal and the frequency correction signal and the added reactive current correction reference signal as a control device for system interconnection inverter, characterized in that it comprises a, adding means for outputting to said current control means.