JPH1141812A - Controller of power system self-excited converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an overcurrent caused by a negative-phase voltage generated by an AC system failure, etc., by a method wherein a voltage at the linkage point of a self-excited converter and an AC system is detected and an negative-phase component contained therein is detected and the voltage signal of the negative-phase component is added to the voltage signal of a positive-phase component to generate a control output. SOLUTION: A voltage at the junction of a self-excited converter and an AC system is detected by an AC voltage transformer 111, and 3-phase AC voltages are converted into 2-phase AC voltages of d-axis and q-axis by a 2nd conversion circuit 112. The positive-phase components of the converted 2-phase signals are detected by positive- phase component detection circuits 113a and 113b and multiplied by a gain. Also, the negative-phase components of the converted 2-phase signals are detected by negative-phase component detection circuits 114a and 114b and multiplied by a gain. A PWM pulse is generated by using signals obtained by adding the negative-phase component voltage signals to other signals by 3rd 4th adding circuits 115 and 116. With this constitution, the negative-phase component in a system voltage is added to a control voltage by feed-forward and an output voltage whose negative-phase component is compensated can be obtained. Therefore, an overcurrent is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a self-excited converter applied to a DC power transmission and a reactive power compensator,
In particular, the present invention relates to a control device for a self-excited converter that can prevent occurrence of overcurrent in the event of an AC system accident.

[0002]

2. Description of the Related Art Since active power and reactive power can be controlled arbitrarily, at high speed, and independently, application of self-excited converters to DC power transmission is being promoted. The self-commutated converter under development is equivalent to a voltage source because it is a voltage type. For this reason, when the fault impedance at the time of AC system failure is small, an overcurrent flows, and the self-excited converter must be stopped for protection, and there is a problem that power transmission reliability is reduced.

[0003]

There are two possible causes of overcurrent when an AC system failure occurs. There are an overcurrent that occurs immediately after the occurrence of a failure and occurs due to a delay in control of the converter, and an overcurrent that occurs after the failure is removed during the failure period and occurs because the negative phase component cannot be sufficiently compensated.

[0004] As a countermeasure for suppressing an overcurrent at the time of failure of the AC system and enabling the continuation of operation, first, there is a high-speed response of a control system. For this reason, in the control circuit of the self-excited converter, the following document "Y. Tokiwa, et al.," Application of a digital
instantaneous current control for static induction
thyristor converters in th utility line ", PCIM'88
As described in Proceeding pp. 343-351, a non-interference vector control method has been considered in which the output AC current of the converter is dq-converted, and the d-axis component and the q-axis component are current-controlled at high speed without interference.

However, when the AC voltage includes a negative phase component due to an unbalanced fault in the AC system, the control output is not reflected because the control for the negative phase component is not performed. Overcurrent flows due to the imbalance in the output voltages of If there is an imbalance of 20% in the system, an overcurrent exceeding twice the rated current (1 + 0.2 / 0.2: assuming the impedance of the conversion transformer is 20%) will flow through the converter. The device must be stopped to protect the device.

An object of the present invention is to provide a control device capable of preventing the occurrence of overcurrent even in the event of an imbalance in an AC system and continuing the operation of the power system self-excited converter.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a self-excited converter for a power system which comprises a self-extinguishing element such as a GTO and converts AC to DC or DC to AC. In a control device controlled by a control output based mainly on a voltage signal of a positive-phase component (a measured value or a positive-phase component detected from a measured value) of an AC voltage at a system point, a connection point between the self-excited converter and an AC system is provided. Means for detecting the voltage of the detected voltage, means for detecting the negative-phase component included in the detected voltage, means for adding the voltage signal of the negative-phase component to the voltage signal of the positive-phase component, based on the added voltage signal. A means for generating the control output is provided to suppress an overcurrent due to a reverse-sequence voltage at the time of an AC system failure or the like.

[0008] Further, by detecting a negative-phase component included in the AC voltage and adding the negative-phase component to the output control signal of the non-interference vector control circuit in a feed-forward manner, a negative-phase component voltage is placed on the output voltage of the self-excited converter. The present invention is characterized in that occurrence of an overcurrent is prevented by eliminating a potential difference from the AC voltage of the system.

The control device for performing the non-interference vector control includes a means for converting an AC voltage into two axes of dq, a means for detecting a positive phase component of each of the converted d-axis and q-axis voltages, Means for detecting a negative-phase component of each axis component voltage, means for adding a signal obtained by multiplying the detected positive-phase component and negative-phase component voltage signals by a gain to the respective d-axis and q-axis control signals, A means for inverting the added control signal from two phases to three phases is provided, and the control output is created based on the inverted three-phase signal.

According to the present invention, the detected voltage of the opposite phase is placed on the output voltage of the self-excited converter to eliminate the potential difference from the AC voltage of the system, thereby preventing the occurrence of overcurrent.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments of the present invention will be described in detail with reference to the drawings. Note that the same reference numerals are given to the same elements throughout the drawings.

FIG. 1 shows a configuration of a control device of a self-excited converter for a power system according to a first embodiment. This embodiment shows an example of application to a DC power transmission system, in which a main circuit is a voltage-type self-excited converter 5 composed of AC systems 1 and 2, conversion transformers 3 and 4, and a self-extinguishing element such as a GTO. , 6, a DC circuit 7 and a capacitor 8 for voltage smoothing. The control device of this example shows only the side of the self-excited converter 6, and the illustration of the side of the self-excited conversion period 5 having the same configuration is omitted.

This control device is an example of performing non-interference vector control, and is configured as follows. An operation command circuit 100 for instructing an operation state of DC power transmission, and an operation command circuit 100
The active power control circuit 101 controls the active power or the DC voltage to a command value according to the active power or the DC voltage command value from the controller, and the reactive power controls the reactive power to the command value according to the reactive power command value from the operation command circuit 100. A power control circuit 102, an AC current detector 103 for detecting a current flowing through the self-excited converter, a first conversion circuit 104 for converting a three-phase AC current into two phases of dq axes, and an active power control circuit 101
And a first addition circuit 105 for calculating a deviation between the output of the first conversion circuit 104 and the output of the first conversion circuit 104. A second adding circuit 106 for calculating a deviation from the q-axis current component Iq, which is an output, and a first arithmetic circuit 107
And a second arithmetic circuit 108.

First adder 105 and first arithmetic circuit 1
07, the d-axis current control circuit (active current control circuit)
Adder circuit 106 and second arithmetic circuit 108 constitute a q-axis current control circuit (reactive current control circuit). A third operation circuit 109 multiplies the converted d-axis current component Id by the impedance of the conversion transformer, and a fourth operation multiplies the converted q-axis current component Iq by the impedance of the conversion transformer. The circuit 110 is provided.

Further, an AC voltage transformer 111 for detecting a voltage of an AC system at a connection point to which the self-excited converter is connected;
A second conversion circuit 112 for converting the three-phase AC voltage into two phases of dq axes; and a positive phase component for extracting a positive phase component from the signal converted to two axes of dq by the second conversion circuit 112 and multiplying the gain by a gain. The detection circuit includes 113a and 113b, and antiphase components detection circuits 114a and 114b that extract the antiphase component from the signal converted into two axes of dq by the second conversion circuit 112 and multiply the gain by a gain.

As shown in FIG. 2, the positive phase component detection circuit 113
Is composed of a filter circuit Fil (1) and an amplifier circuit AMP (1). FIG. 3 shows the input / output characteristics of the filter circuit Fil (1). Since the positive phase component is a DC signal, a low-pass filter characteristic may be used. As shown in FIG. 4, the anti-phase component detection circuit 114 includes a band-pass filter circuit Fil (2) and an amplifier circuit AMP (2). FIG. 5 shows the input / output characteristics of the band-pass filter circuit Fil (2). Since the opposite phase component is a double frequency of the fundamental wave, it has a bandpass filter characteristic having a center frequency at the double frequency.

Further, the d-axis current control value by the first arithmetic circuit 107, the compensation voltage conversion value of the impedance drop by the q-axis current component Iq by the fourth arithmetic circuit 110, and the positive-phase component by the positive-phase component detection circuit 113 Voltage signal Vd
p and the voltage signal V of the negative phase by the negative phase detection circuit 114
Similarly to the third adding circuit 115 for adding dn,
, The q-axis current control value by the arithmetic circuit 108, the compensation voltage conversion value of the impedance drop by the current component Id by the third arithmetic circuit 109, the positive-phase voltage signal Vqp and the negative-phase component detection circuit by the positive-phase component detection circuit 113. Fourth adding circuit 11 for adding voltage signal Vqn for the opposite phase by 114
6, a third conversion circuit 117 for inversely converting a two-phase signal of the d-axis control output of the third addition circuit 115 and the q-axis control output of the fourth addition circuit 116 into a three-phase signal, PWM according to the three-phase reference voltage signal output from the conversion circuit 117
It has a PWM pulse generating circuit 118 for generating a pulse. The generated PWM pulse becomes a control voltage for controlling on / off of each element of the voltage type self-excited converters 5, 6, that is, a control output.

As described above, according to the control device of the present embodiment, the negative-phase component included in the system voltage is fed forward and added to the control voltage output from the control device. The output voltage is compensated for. This eliminates the difference between the system voltage and the output voltage,
No overcurrent occurs in the self-excited converters 5, 6.

Next, the operation of DC power transmission by the self-excited converter of this embodiment will be described. The self-excited converter 5 is a forward converter,
It is assumed that the self-excited converter 6 is operated by an inverter, the forward converter 5 controls active power, and the inverter 6 controls a DC voltage. Conversely, even when the DC voltage is controlled by the forward converter and the active power is controlled by the inverse converter, the self-excited converter controls the phase and magnitude of the AC output voltage so that the DC voltage is maintained at the specified value. Or the control of the phase and magnitude of the AC output voltage so as to keep the active power at the specified value, and there is no difference in the control operation in either case.

The active power control circuit 101 of the control device on the side of the forward converter receives an active power command value from the operation command circuit 100 and changes the output AC voltage of the self-excited converter 5 so that the active power becomes a specified value. Control. On the other hand, the active power control circuit 101 of the control device on the inverter side receives a DC voltage command value from the operation command circuit 100 and controls the output AC voltage of the self-excited converter 6 so that the DC voltage becomes a specified value. I do.

Here, it is assumed that a negative phase component is superimposed on the AC voltage on the inverter side due to an imbalance failure in the AC system on the inverter side. Normally, AC voltage is balanced in three phases,
The output of 14 is zero, but when it becomes unbalanced, a reverse phase component is detected. Since the antiphase component is a double frequency of the fundamental wave, a band-pass filter Fil having a center frequency at the double frequency is used.
It is detected by the characteristic of (2), and the gain is multiplied by AMP (2).

The negative phase component detection circuits 114a and 114b detect the negative phase voltage components Vdn and Vqn from the d-axis voltage component Vd and the q-axis voltage component Vq by the second conversion circuit 112, respectively. 4 to the adders 115 and 116.

The adder 115 adds a negative phase voltage Vdn to the control value of the current component Id or the positive phase voltage Vdp of the positive phase of the d-axis component to generate a d-axis control signal.
Numeral 16 adds a negative-sequence voltage Vqn to a control value of the current component Iq and a positive-phase voltage Vqp for the positive phase of the q-axis component to create a q-axis control signal, and sends them to the third conversion circuit. Output.

The third conversion circuit 117 includes the addition circuit 11
The d and q two-phase signals from 5,116 are converted into three-phase signals, and a three-phase voltage reference signal to which an anti-phase component is added is created. Further, the PWM pulse generation circuit 118 generates a PWM signal for obtaining an AC output voltage equivalent to the three-phase voltage reference signal.
M pulses are created.

As described above, the negative phase component included in the AC system voltage is added to the d-axis and q-axis control signals in a feedforward manner, and the self-excited converter 6 obtains an AC output voltage in which the negative phase component is compensated. Therefore, the difference between the output voltage and the system voltage is reduced to prevent an overcurrent from flowing to the self-excited converter.

Next, a second embodiment of the present invention will be described. In the control device of the self-excited converter of FIG. 1 according to the first embodiment, a negative-phase component included in the voltage of the AC system is detected, and the same negative-phase component as the system voltage is output to the output voltage of the self-excited converter. However, in the second embodiment, the reverse-phase component is detected from the current flowing in the system, and the current command value is corrected.

FIG. 6 shows a configuration of a control device of the power self-excited converter according to the second embodiment. Explaining the points different from FIG. 1, Id, Vd and Vq are replaced with detection circuits 113 and 114 for detecting the positive-phase and negative-phase voltages.
That is, a detection circuit 120 for detecting the current of the opposite phase from Iq is provided.

The antiphase component detection circuit 120a extracts the antiphase component from the d-axis current component Id of the first conversion circuit 104 and multiplies the gain by a gain. The basic configuration of the detection circuit may be the same as FIG.
Bandpass filter circuit Fil (2) and amplifier circuit AMP
It consists of (2). The negative-phase component detection circuit 120b extracts the negative-phase component from the q-axis current component Iq of the first conversion circuit 104 and multiplies it by a gain. Other than that, only the input signal changes from Id to Iq.

The current signal for the negative phase of the current component Id is subtracted by the fifth adding circuit 121 from the command value for the d-axis current control of the active power control circuit 101. Further, the current signal of the negative phase of the current component Iq is subtracted by the sixth adding circuit 122 from the command value of the q-axis current control of the reactive power control circuit 102.

As a result, the command value for the d-axis current control and the command value for the q-axis current control are values corrected by the negative phase component included in the AC current. These current command values and Vd, Vq
Thus, the d-axis control signal and the q-axis control signal are generated by the adders 115 and 116 in the same manner as in the case of FIG.

According to the control device of this embodiment, the control output is performed according to the current command value corrected by the negative phase component of the AC system. Normally, the output of the negative phase detecting circuits 120a and 120b is zero because the negative phase component is not included in the current flowing through the system. If a negative phase component is included in the system current due to a failure or the like, a detection value is output to the negative phase component detection circuits 120a and 120b, and the negative phase component is subtracted from the current command value. The output voltage of the self-excited converter is controlled by the control output of the control device so that a current corresponding to the current command value flows to the output of the converter. In other words, so that the current of the negative phase due to the negative phase voltage does not flow,
Since the output voltage of the self-excited converter is controlled, it is possible to prevent the occurrence of overcurrent due to the reverse phase voltage at the time of a system failure.

A third embodiment according to the present invention will be described. In the second embodiment shown in FIG. 6, a configuration is employed in which a negative phase component of a current flowing through a system is detected, and the detected negative phase component is added to a command value of a current control circuit so that a negative phase current does not flow. However, in the third embodiment, the reverse phase component of the current is detected, and this is converted into a voltage and compensated by feedforward as in FIG.

FIG. 7 shows a configuration of a control device of a self-excited converter for a power system according to a third embodiment. The difference from FIG. 6 will be described. The negative-phase current detecting circuits 120a and 120b
, A negative-phase detection / conversion circuit 130a, which detects a current of the negative phase from Id and Iq and further converts the current into a voltage signal.
b.

The negative phase detection / conversion circuit 130a extracts the negative phase component from the d-axis current component Id of the first conversion circuit 104, and performs gain multiplication including voltage conversion. The circuit configuration is shown in FIG.
And may include a band-pass filter circuit Fil (2) and an amplifier circuit AMP (2). Amplifier circuit AMP (2)
Has a function of converting a current signal into a voltage signal. The coefficient for converting the current into the voltage has a gain that is a value obtained by adding the attenuation corresponding to the loop of the negative-phase-sequence control circuit to the impedance corresponding to the leakage reactance of the conversion transformer.

The antiphase component detection / conversion circuit 130b extracts the antiphase component from the q-axis current component Iq output from the first conversion circuit 104, and performs gain multiplication. Input signal is Id to Iq
The configuration is the same except for the change.

The operation of this embodiment is the same as that of the first embodiment described with reference to FIG. 1, and it is possible to prevent the occurrence of an overcurrent due to a reverse-phase voltage at the time of a system failure.

In the above embodiment, a band-pass filter having a center frequency twice as high as the commercial frequency is used as a means for detecting a negative-phase component from the detected AC voltage or AC current. You can also ask. In this case, the first conversion circuit 104, the second conversion circuit 112, and the anti-phase component detection circuits 120a, b, 130a, b become unnecessary. The detection of the negative phase component is obtained by the equations (1) and (2).

[0038]

(Equation 1)

Equation (1) is an equation for obtaining an alternating current, and equation (2) is an equation for obtaining a negative-phase component of an AC voltage. Iu, Iv, and Iw are three-phase instantaneous value currents, and Vu, Vv, and Vw are instantaneous value voltages. , E (j2π
/ 3) indicates that it advances by 2π / 3, and e (−j2π /
3) indicates that the delay is 2π / 3.

Since the negative phase component is an AC signal having a double frequency, to obtain Idn and Vdn as control signals,
The DC component may be obtained by taking the absolute values of the equations (1) and (2).

FIG. 8 shows an example in which the control device for a self-excited converter of the present invention is applied to a reactive power compensator. The reactive power compensator is composed of a self-excited converter.

In brief, an AC system 1 and a load 1
0, a conversion transformer 11 for system-linking the self-excited reactive power compensator, a voltage-type self-excited converter 1 composed of GTO, etc.
2, and the power capacitor 13 on the DC side of the self-excited converter,
An AC current transformer 203 for detecting an output AC current of the self-excited converter, an AC voltage transformer 211 for detecting a voltage at a connection point connecting the self-excited reactive power compensator and the AC system, and a reactive power of the converter. It comprises an operation command circuit 200 of a self-excited reactive power compensator using a DC voltage value as a command value, and a control device 201.

The control device 201 is provided in accordance with FIG. 1, FIG. 6 or FIG.
Of the control device. The AC current transformer 203 and the AC voltage transformer 211 detect a current and a voltage necessary for control of the control device 201 and are taken into the control device 201. The operation of the control device 201 is the same as that of the first to third embodiments except that the command value from the operation command circuit 200 is different. By applying the control device of the present invention, it is possible to prevent the occurrence of overcurrent due to the reverse-phase voltage at the time of a system failure of the self-excited var compensator.

[0044]

According to the present invention, an overcurrent is generated even in the event of an imbalance in an AC system by a simple change of a conventional control device such as addition of means for detecting an invalid component of the voltage or current of the AC system. The operation can be continued without performing, and the operation reliability of the SVC or HVDC to which the self-excited converter is applied can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a control device of a power self-excited converter according to a first embodiment of the present invention and its application to a DC transmission system.

FIG. 2 is a configuration diagram of a positive phase component detection circuit.

FIG. 3 is an explanatory diagram illustrating filter characteristics of a positive-phase-sequence detection circuit.

FIG. 4 is a configuration diagram of an antiphase component detection circuit.

FIG. 5 is an explanatory diagram showing filter characteristics of an antiphase component detection circuit.

FIG. 6 is a configuration diagram of a control device of a power self-excited converter according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a control device of a power self-excited converter according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram of a self-excited var compensator provided with the control device of the present invention.

[Explanation of symbols]

1,2 ... AC system, 3,4,11 ... Conversion transformer, 5,
6, 12: self-excited converter, 7: DC circuit, 8: capacitor for voltage smoothing, 10: load, 13: power capacitor, 100, 200: operation command circuit, 101: active power control circuit, 102: invalid Power control circuit, 103, 203
... AC current detector, 104 ... first conversion circuit, 105 ...
1st addition circuit, 106 ... 2nd addition circuit, 107 ... 1st arithmetic circuit, 108 ... 2nd arithmetic circuit, 109 ... 3rd
Arithmetic circuit 110, fourth arithmetic circuit 111, 211
... AC voltage transformer, 112 ... second conversion circuit, 113
a, b: positive phase detection circuit, 114a, b: reverse phase detection circuit, 115: third addition circuit, 116: fourth addition circuit, 117: third conversion circuit, 118: PWM pulse generation circuit , 120a, b... Anti-phase component detection circuit, 121.
, A sixth addition circuit, and 130a, b ...
Negative phase detection / conversion circuit, 201 ... Control device.

Continued on the front page (72) Inventor Toshiyuki Hayashi 2-1-1, Iwatokita, Komae-shi, Tokyo Inside the Central Research Institute of Electric Power Industry (72) Inventor Masahiro Takasaki 2-1-1, Iwatokita, Komae-shi, Tokyo Foundation Within the Central Research Institute of Electric Power Industry (72) Inventor Naoki Giho 2-1-1, Iwatokita, Komae-shi, Tokyo Inside the Central Research Institute of Electric Power Industry

Claims (10)

[Claims] 1. A self-extinguishing element such as GTO,
A self-excited power system converter that converts AC to DC or DC to AC is controlled by a control output based on a voltage command value and a voltage signal of mainly the positive-phase component of the AC voltage at the AC / DC interconnection point. In the converter control device, a means for detecting a voltage at an interconnection point between the self-excited converter and the AC system, a means for detecting a negative-phase component included in the detected voltage, and a voltage signal of the negative-phase component Means for adding to the voltage signal of the positive-phase component and means for creating the control output based on the added voltage signal are provided to suppress overcurrent due to reverse-phase voltage such as at the time of AC system failure. Control device for self-excited converter for power system. 2. The apparatus according to claim 1, wherein the means for converting the AC voltage into two axes of dq, means for detecting the positive-phase components of the converted voltages of the d-axis and the q-axis, and each of the converted dq-axis components Means for detecting the negative-phase component of the voltage, means for adding a signal obtained by multiplying the detected positive-phase component and negative-phase component voltage signals by a gain to each of the d-axis and q-axis control signals, and the added control. A control device for a power system self-excited converter, comprising: means for inverting a signal from two phases to three phases, and generating the control output based on the inverted three-phase signal. 3. The control device for a power system self-excited converter according to claim 1, wherein the means for detecting the positive-phase component comprises a low-pass filter. 4. The control device for a power system self-excited converter according to claim 1, wherein the means for detecting the anti-phase component comprises a band-pass filter having a center frequency of twice a fundamental wave. . 5. A self-extinguishing element such as GTO,
In a control device for controlling a power system self-excited converter for converting alternating current to direct current or direct current to alternating current by a control output based on a current command value and a current signal of mainly a positive-phase component of an alternating current at an AC / DC interconnection point, A means for detecting a current flowing from the self-excited converter to the AC system, a means for detecting a negative-phase component included in the detected current, and a means for adding the negative-phase component to the current command value. A control device for a self-excited converter for a power system, characterized by suppressing an overcurrent due to a negative-sequence voltage. 6. The method according to claim 5, wherein the means for converting the detected AC current into two axes of dq, a means for detecting a negative-phase component of each converted current, and a current signal of each of the detected negative-phase components. A control device for a power system self-excited converter, comprising means for multiplying a gain and adding the current command value to each of a d-axis and a q-axis. 7. The control device for a power system self-excited converter according to claim 5, wherein the means for detecting the anti-phase component comprises a band-pass filter having a center frequency of twice a fundamental wave. . 8. A self-extinguishing element such as GTO,
In a control device for controlling a self-excited converter for a power system that converts alternating current to direct current or direct current to alternating current by a control output based on a voltage command value and a voltage signal of mainly a positive-phase component of an AC voltage at an AC / DC interconnection point, Means for detecting a current flowing from the self-excited converter to the AC system, means for detecting a negative-phase component included in the detected current, means for converting a current value of the detected negative-phase component into a voltage signal, A means for adding the voltage signal of the negative phase component to the voltage signal of the positive phase component, and a means for generating the control output based on the added voltage signal; A control device for a self-excited converter for a power system, characterized in that the control is performed. 9. The means according to claim 8, wherein said means for converting the detected AC current into two axes of dq, means for detecting each of the negative-phase components of the converted dq-two-axis current signal, and the detected negative-phase current A control device for a power system self-excited converter, comprising: means for converting a signal into a voltage signal; and means for adding the converted voltage signal to each of the control signals for the d-axis and the q-axis. 10. The control device for a power system self-excited converter according to claim 8, wherein the means for detecting the negative-phase component includes a band-pass filter having a center frequency twice the fundamental wave. .