JP2011115018A - Self-exciting reactive-power compensator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform parallel actuation of a plurality of self-exciting reactive-power compensator capable of assuring controlling performance in a certain level, and reducing a switching loss. <P>SOLUTION: The self-exciting reactive-power compensator 101 is equipped with self-exciting converters 1, 2 each connected to a power system 3 having a plurality of phases, including switching elements, and converting a supplied DC voltage to an AC voltage to output a reactive power to the power system 3; a first current detector 3 to detect a first current output from the self-exciting converter 1 to the power system 3; a second current detector 4 to detect a second current output from the self-exciting converter 2 to the power system 3; and a converter controller 10 to control the current output from the self-exciting converters 1, 2 to the power system 3, by making the switching elements switch based on the resultant value and the differential value of the first and the second currents. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a self-excited reactive power compensator, and more particularly to a self-excited reactive power compensator used in a power system.

  A self-reactive reactive power compensator called STATCOM (Static Synchronous Compensator), SVG (Static Var Generator), or self-excited SVC (Static Var Compensator) is used to improve system stability by controlling system reactive power. Often introduced. The self-excited reactive power compensator is effective not only for improving the stability of the system during steady operation, but also for improving the transient stability of the system during and after a system fault.

  In order to achieve the above object, the control unit of the self-excited reactive power compensator is generally configured as follows. That is, the control unit outputs a reactive current command so that the system voltage follows the desired system voltage command (main loop), and power so that the output current of the power converter follows this reactive current command. A current control loop (secondary loop) for controlling the output voltage of the converter.

  For example, in Non-Patent Document 1, the control unit in STATCOM controls AVR (automatic voltage regulator) control for improving the synchronization force in the first wave of transient fluctuations, and suppresses fluctuations after the second wave. A configuration for performing PSS (Power System Stabilizer) control is disclosed.

1991 Institute of Electrical Engineers, Power and Energy Division Conference, pp. 683-686

  In order to improve the reliability against a grid fault and a failure of the STATCOM itself, there are cases where two STATCOMs are independently operated in parallel for the same power system. However, in such a configuration, in order to ensure a certain level of control performance in the two STATCOMs, it is necessary to set the number of pulses per fixed time given to the power converter to a certain value or more in each STATCOM. For this reason, a switching loss will increase compared with the case where one STATCOM is used.

  The present invention has been made to solve the above-described problems, and its object is to reduce the switching loss while ensuring a certain level of control performance by operating a plurality of self-excited reactive power compensators in parallel. It is to provide a possible self-excited reactive power compensation system.

  In order to solve the above-described problems, a self-excited reactive power compensator according to an aspect of the present invention includes a switching element, each of which is coupled to a power system having a plurality of phases, and the supplied DC voltage is converted into an AC voltage. A first self-excited converter and a second self-excited converter for converting reactive power to the power system and outputting current from the first self-excited converter to the power system. A first current detector for detecting, a second current detector for detecting a current output from the second self-excited converter to the power system, and a current detected by the first current detector And a combined value of the current detected by the second current detector and a difference value between the current detected by the first current detector and the current detected by the second current detector. The first self-excited variable And a converter that controls the current output from the first self-excited converter and the second self-excited converter to the power system by switching the switching element in the converter and the second self-excited converter. A controller.

  According to the present invention, a plurality of self-excited reactive power compensators can be operated in parallel to reduce switching loss while ensuring a certain level of control performance.

It is a figure which shows the structure of the self-excitation reactive power compensation apparatus which concerns on the 1st Embodiment of this invention. 1 is a circuit diagram of a first group self-excited converter 1. FIG. It is a figure for demonstrating the control content of the converter control part which concerns on the 1st Embodiment of this invention. It is a figure which shows the gate pulse signal in the self-excitation reactive power compensation apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the self-excitation type reactive power compensation apparatus which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the control content of the converter control part which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a diagram showing a configuration of a self-excited reactive power compensator according to the first embodiment of the present invention.

  Referring to FIG. 1, a self-excited reactive power compensator 101 includes a first group self-excited converter 1, a second group self-excited converter 2, current detectors 3 and 4, a system voltage detector 5, and a conversion. Transformer transformers 8 and 9 and a converter control unit 10 are provided.

  The first group self-excited converter 1 is coupled to a power system 60 having a u phase, a v phase, and a w phase, includes a self-extinguishing type switching element, converts a DC voltage supplied from the outside into an AC voltage, By outputting the converted AC voltage to the power system 60, reactive power is output to the power system 60. The converter transformer 8 transforms the AC voltage output from the first group self-excited converter 1 and outputs it to the power system 60.

  The second group self-excited converter 2 is coupled to a power system 60 having u-phase, v-phase, and w-phase, includes a self-extinguishing type switching element, converts a DC voltage supplied from the outside into an AC voltage, By outputting the converted AC voltage to the power system 60, reactive power is output to the power system 60. The converter transformer 9 transforms the AC voltage output from the second group self-excited converter 2 and outputs it to the power system 60.

  The reactive power output from the first group self-excited converter 1 and the reactive power output from the second group self-excited converter 2 are combined and supplied to the power system 60.

FIG. 2 is a circuit diagram of the first group self-excited converter 1.
Referring to FIG. 2, group 1 self-excited converter 1 includes switching elements Q1-Q6, diodes D1-D6, and a smoothing capacitor C1. The switching elements Q1 to Q6 are, for example, GTO (Gate Turn Off thyristor), but are not limited to this as long as they are self-extinguishing type switching elements. Diodes D1-D6 are connected in antiparallel to switching elements Q1-Q6, respectively. The smoothing capacitor C1 smoothes the external DC voltage.

  A driving signal (gate pulse signal) is supplied from the converter control unit 10 to each of the switching elements Q1 to Q6. The switching elements Q1 to Q6 perform a switching operation based on the drive signal, convert the voltage smoothed by the smoothing capacitor C1, that is, a DC voltage into an AC voltage, and supply the AC voltage to the power system 60.

  Since the configuration of the second group self-excited converter 2 is the same as that of the first group self-excited converter 1, detailed description thereof will not be repeated here.

  FIG. 3 is a diagram for explaining the control contents of the converter control unit according to the first embodiment of the present invention. Reference numerals in FIG. 3 correspond to the reference numerals of the blocks in FIG.

  Referring to FIGS. 1 and 3, current detector 3 detects a current output from first group self-excited converter 1 to power system 60. The current detector 4 detects a current output from the second group self-excited converter 2 to the power system 60. The current detected by the current detector 3 and the current detected by the current detector 4 are given to the converter controller 10 as a feedback current. The system voltage detector 5 detects the voltage (system voltage) of the power system 60. The voltage detected by the system voltage detector 5 is given to the converter control unit 10 as a feedback voltage.

  Next, the converter control unit 10 will be described in detail. The converter control unit 10 includes a combined reactive current reference calculation unit 11, a combining unit 12, a combined reactive current detection unit 13, a combined reactive current control unit 14, a combined active current detection unit 15, and a combined effective current control unit. 16, a subtraction unit 17, a circulation reactive current detection unit 18, a circulation reactive current control unit 19, a circulation effective current detection unit 20, a circulation effective current control unit 21, a reference value conversion unit 22, and a first group gate A pulse signal generation unit 23 and a second group gate pulse signal generation unit 24 are included.

  The converter control unit 10 includes a combined value of the current detected by the current detector 3 and the current detected by the current detector 4, the current detected by the current detector 3 and the current detected by the current detector 4. From the first group self-excited converter 1 and the second group self-excited converter 2 by switching the switching elements Q1 to Q6 in the first group self-excited converter 1 and the second group self-excited converter 2 based on the difference value of The current output to the power system 60 is controlled.

  More specifically, the combining unit 12 calculates a combined value of the current I1 detected by the current detector 3 and the current I2 detected by the current detector 4.

  The combined reactive current detection unit 13 is based on the combined value calculated by the combining unit 12, and the reactive current output from the first group self-excited converter 1 to the power system 60 and the second group self-excited converter 2 to the power system 60. The composite current of the reactive current output to (the composite reactive current) is detected.

  Based on the system voltage VA detected by the system voltage detector 5, the composite reactive current reference calculation unit 11 performs AVR control to calculate the target value IREF1 of the composite reactive current so that the system voltage VA becomes a predetermined voltage value. Do.

  The combined reactive current control unit 14 outputs the reactive voltage output from the first group self-excited converter 1 and the second group self-excited converter so that the combined reactive current detected by the combined reactive current detection unit 13 becomes the target value IREF1. The reference value of the composite voltage (composite reactive voltage) of the reactive voltage output from 2 is calculated. The combined reactive current control unit 14 performs level control of the AC voltage output from the first group self-excited converter 1 and the AC voltage output from the second group self-excited converter 2.

  The combined reactive current reference calculation unit 11 is configured to perform AVR control, but is not limited thereto. The combined reactive current reference calculation unit 11 may perform PSS control that outputs reactive power so as to suppress fluctuations in system power. That is, the system power control unit 19 may be configured to calculate the transmission power in the power system and calculate the target value IREF1 based on the calculated transmission power. Alternatively, the combined reactive current reference computation unit 11 computes a target value IREF1 for biasing reactive power output from the first group self-excited converter 1 and second group self-excited converter 2 to the power system 60. The structure which performs control may be sufficient. In other words, the combined reactive current reference calculation unit 11 receives the necessary reactive power Q indicating the minimum reactive power value to be supplied to the power system 60, and from the first group self-excited converter 1 and the second group self-excited converter 2. The configuration may be such that the target value IREF1 of the combined reactive current for outputting the necessary reactive power Q is calculated.

  Based on the combined value calculated by the combining unit 12, the combined effective current detection unit 15 outputs the effective current output from the first group self-excited converter 1 to the power system 60 and the second group self-excited converter 2 from the power system 60. The combined current of the effective current output to (the combined effective current) is detected.

  The combined effective current control unit 16 outputs the effective voltage output from the first group self-excited converter 1 and the second group self-excited converter so that the combined effective current detected by the combined effective current detection unit 15 becomes the target value IREF2. The reference value of the composite voltage (composite effective voltage) of the effective voltage output from 2 is calculated. The composite active current control unit 16 performs phase control of the AC voltage output from the first group self-excited converter 1 and the AC voltage output from the second group self-excited converter 2.

  Here, the target value IREF2 corresponds to a DC voltage to be supplied to the first group self-excited converter 1 and the second group self-excited converter 2. The combined effective current control unit 16 sets the reference value of the combined effective voltage so that an effective voltage equivalent to the case where this DC voltage is obtained is output from the first group self-excited converter 1 and the second group self-excited converter 2. Calculate. Further, the target value IREF2 may be a fixed value or a fluctuation value obtained by some calculation.

  The subtracting unit 17 calculates a difference value between the current detected by the current detector 3 and the current detected by the current detector 4.

  The circulating reactive current detector 18 detects a circulating reactive current flowing between the first group self-excited converter 1 and the second group self-excited converter 2 based on the difference value calculated by the subtracting section 17.

  The circulation reactive current control unit 19 is applied between the first group self-excited converter 1 and the second group self-excited converter 2 so that the circulation reactive current detected by the circulation reactive current detection unit 18 becomes the target value IREF3. The reference value of the circulating reactive voltage that is the reactive voltage is calculated. The circulation reactive current control unit 19 performs level control of the AC voltage output from the first group self-excited converter 1 and the AC voltage output from the second group self-excited converter 2. The target value IREF3 is set to, for example, zero in order to make the current capacities of the first group self-excited converter 1 and the second group self-excited converter 2 uniform. Further, the target value IREF3 may be a fixed value or a fluctuation value obtained by some calculation.

  The circulating effective current detection unit 20 detects the circulating effective current flowing between the first group self-excited converter 1 and the second group self-excited converter 2 based on the difference value calculated by the subtracting unit 17.

  The circulating effective current control unit 21 is applied between the first group self-excited converter 1 and the second group self-excited converter 2 so that the circulating effective current detected by the circulating effective current detection unit 20 becomes the target value IRFE4. The reference value of the circulating effective voltage that is the effective voltage is calculated. In the circulating effective current control unit 21, phase control of the AC voltage output from the first group self-excited converter 1 and the AC voltage output from the second group self-excited converter 2 is performed.

  Here, target value IRFE4 indicates, for example, a circulating effective current value such that the difference in DC voltage to be applied to group 1 self-excited converter 1 and group 2 self-excited converter 2 is zero. Further, the target value IRFE4 may be a fixed value or a fluctuation value obtained by some calculation.

  The reference value converter 22 outputs the voltage output from the group 1 self-excited converter 1 based on the reference value of the combined reactive voltage, the reference value of the combined effective voltage, the reference value of the circulating reactive voltage, and the reference value of the circulating effective voltage. The reference value VREF1 and the reference value VREF2 of the voltage output from the second group self-excited converter 2 are calculated.

  The first group gate pulse signal generation unit 23 outputs a first group gate pulse signal for the first group self-excited converter 1 to output a voltage corresponding to the reference value VREF1 according to, for example, PWM (Pulse Width Modulation) control. It supplies to switching elements Q1-Q6 in converter 1.

  The second group gate pulse signal generator 24 switches the second group gate pulse signal in the second group self-excited converter 2 so that the second group self-excited converter 2 outputs a voltage corresponding to the reference value VREF2 according to, for example, PWM control. Supply to the elements Q1 to Q6.

  The reference value VREF1 and the reference value VREF2 are obtained by converting the combined reactive current detected by the combined reactive current detection unit 13 to the voltage feedback control system using the system voltage detected by the system voltage detector 5 in the combined reactive current control unit 14. It is obtained as the output of the control system with the current minor loop control used. With this control system, the reference value VREF1 and the reference value VREF2 can be changed following the change in the system voltage.

  FIG. 4 is a diagram showing a gate pulse signal in the self-excited reactive power compensator according to the first embodiment of the present invention.

  Referring to FIG. 4, first group gate pulse signal generation unit 23 and second group gate pulse signal generation unit 24 are connected to each other based on reference value VREF 1 and reference value VREF 2 received from reference value conversion unit 22. The phase is shifted and output. More specifically, the pulses are output so that the pulses of the first group gate pulse signal and the pulses of the second group gate pulse signal exist alternately on the time axis. As a result, the synthesized gate pulse signal obtained by synthesizing the first group gate pulse signal and the second group gate pulse signal has twice as many pulses as the first group gate pulse signal and the second group gate pulse signal.

  Therefore, even if the number of pulses per fixed time given to each of the first group self-excited converter 1 and the second group self-excited converter 2 is set to 1/2, The frequency of PWM control for the excitation converter can be doubled.

  In the self-excited reactive power compensator 101, the converter control unit 10 detects the combined value of the current detected by the current detector 3 and the current detected by the current detector 4 and the current detector 3. By switching the switching elements Q1 to Q6 in the first group self-excited converter 1 and the second group self-excited converter 2 based on the current and the difference value of the current detected by the current detector 4, the first group self-excited conversion The current output from the power generator 1 and the group 2 self-excited converter 2 to the power system 60 is controlled. That is, two STATCOMs are not independently operated in parallel for the same power system, but the first group self-excited converter 1 and the second group self-excited converter 2 are controlled by a common control system. With this configuration, the entire self-excited reactive power compensator 101 is controlled by the sum of the number of pulses per unit time given to the first group self-excited converter 1 and the number of pulses per unit time given to the second group self-excited converter 2. Since the performance is determined, the self-excited reactive power compensator 101 as a whole can ensure a certain level of control performance. As a result, the number of pulses per unit time given to the first group self-excited converter 1 and the second group self-excited converter 2 can be halved as compared with the prior art, so that the switching loss can be reduced.

  Therefore, in the self-excited reactive power compensator according to the first embodiment of the present invention, a plurality of self-excited reactive power compensators can be operated in parallel to reduce switching loss while ensuring a certain level of control performance. it can.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Second Embodiment>
The present embodiment relates to a self-excited reactive power compensator in which feedback control of a DC voltage supplied to a self-excited converter is added as compared with the self-excited reactive power compensator according to the first embodiment. The contents other than those described below are the same as those of the self-excited reactive power compensator according to the first embodiment.

  FIG. 5 is a diagram showing a configuration of a self-excited reactive power compensator according to the second embodiment of the present invention. FIG. 6 is a diagram for explaining the control contents of the converter control unit according to the second embodiment of the present invention. Reference numerals in FIG. 6 correspond to the reference numerals of the blocks in FIG.

  5 and 6, self-excited reactive power compensator 102 further includes DC voltage detectors 6 and 7 as compared with self-excited reactive power compensator according to the first embodiment of the present invention. And a converter control unit 30 instead of the converter control unit 10.

  Compared with the converter control unit according to the first embodiment of the present invention, the converter control unit 30 further includes a combined DC voltage control unit 25, a DC voltage balancing control unit 26, a combining unit 27, A subtractor 28.

  The DC voltage detector 6 detects a DC voltage supplied to the first group self-excited converter 1. The DC voltage detector 7 detects the DC voltage supplied to the second group self-excited converter 2. The DC voltage detected by the DC voltage detector 6 and the DC voltage detected by the DC voltage detector 7 are given to the converter control unit 30 as a feedback voltage.

  The converter control unit 30 includes a combined value of the current detected by the current detector 3 and the current detected by the current detector 4, the current detected by the current detector 3 and the current detected by the current detector 4. Between the DC voltage detected by the DC voltage detector 6 and the DC voltage detected by the DC voltage detector 7, and the DC voltage detected by the DC voltage detector 6 and the DC voltage detector 7. The first group self-excited converters 1 and 2 are switched by switching the switching elements Q1 to Q6 in the first group self-excited converter 1 and the second group self-excited converter 2 based on the difference value of the DC voltage detected by The current output from the self-excited converter 2 to the power system 60 is controlled.

  More specifically, the combining unit 27 calculates a combined value of the DC voltage VD1 detected by the DC voltage detector 6 and the DC voltage VD2 detected by the DC voltage detector 7.

  The combined DC voltage control unit 25 calculates the target value IREF2 of the combined effective current so that the combined value calculated by the combining unit 27 becomes the target value VREF3. The target value VREF3 may be a fixed value or a fluctuation value obtained by some calculation.

  The subtractor 28 calculates a difference value between the DC voltage VD1 detected by the DC voltage detector 6 and the DC voltage VD2 detected by the DC voltage detector 7.

  The DC voltage balancing control unit 26 calculates the target value IREF4 of the circulating effective current so that the subtraction value calculated by the subtraction unit 28 becomes the target value VREF4. The target value IREF4 may be a fixed value or a fluctuation value obtained by some calculation.

  The combined effective current control unit 16 calculates the reference value of the combined effective voltage so that the combined effective current detected by the combined effective current detection unit 15 becomes the target value IREF2 calculated by the combined DC voltage control unit 25.

  The circulation effective current control unit 21 calculates the reference value of the circulation effective voltage so that the circulation effective current detected by the circulation effective current detection unit 20 becomes the target value IREF4 calculated by the DC voltage balancing control unit 26. .

  Since other configurations and operations are the same as those of the self-excited reactive power compensator according to the first embodiment, detailed description thereof will not be repeated here.

  As described above, in the self-excited reactive power compensator according to the second embodiment of the present invention, the direct-current voltage supplied to the first group self-excited converter 1 and the direct current supplied to the second group self-excited converter 2. By performing voltage feedback control, better reactive power compensation can be performed as compared with the self-excited reactive power compensator according to the first embodiment of the present invention.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 1-group self-excited converter, 2 2-group self-excited converter, 3, 4 current detector, 5 system voltage detector, 6, 7 DC voltage detector, 8, 9 converter transformer, 10, 30 converter Control unit, 12 synthesis unit, 13 synthesis reactive current detection unit, 14 synthesis reactive current control unit, 15 synthesis active current detection unit, 16 synthesis active current control unit, 17 subtraction unit, 18 circulation reactive current detection unit, 19 circulation reactive current Control unit, 20 circulation effective current detection unit, 21 circulation effective current control unit, 22 reference value conversion unit, 23 first group gate pulse signal generation unit, 24 second group gate pulse signal generation unit, 25 combined DC voltage control unit, 26 DC Voltage balancing control unit, 27 synthesis unit, 28 subtraction unit, 101, 102 self-excited reactive power compensator, Q1-Q6 switching element, D1-D6 diode, C1 smoothing capacitor.

Claims (3)

A first self-excited converter, each coupled to a power system having a plurality of phases, including a switching element, for converting a supplied DC voltage into an AC voltage and outputting reactive power to the power system; A second self-excited converter;
A first current detector for detecting a current output from the first self-excited converter to the power system;
A second current detector for detecting a current output from the second self-excited converter to the power system;
A combined value of the current detected by the first current detector and the current detected by the second current detector, the current detected by the first current detector, and the second current detector Switching the switching elements in the first self-excited converter and the second self-excited converter based on the difference value of the current detected by the first self-excited converter and the second self-excited converter A self-excited reactive power compensator comprising a converter control unit that controls a current output from the two self-excited converters to the power system. The converter controller is
Reactive current output from the first self-excited converter to the power system based on a combined value of the current detected by the first current detector and the current detected by the second current detector And a combined reactive current detector that detects a combined reactive current of the reactive current output from the second self-excited converter to the power system,
The reactive voltage output from the first self-excited converter and the invalid output from the second self-excited converter so that the composite reactive current detected by the composite reactive current detector becomes a target value. A combined reactive current control unit for calculating a reference value of the combined reactive voltage of the voltage;
An effective current output from the first self-excited converter to the power system based on a combined value of the current detected by the first current detector and the current detected by the second current detector And a combined active current detector that detects a combined active current of active current output from the second self-excited converter to the power system,
The effective voltage output from the first self-excited converter and the effective output output from the second self-excited converter so that the combined effective current detected by the combined effective current detection unit becomes a target value. A combined effective current control unit for calculating a reference value of the combined effective voltage of the voltage;
Based on the difference value between the current detected by the first current detector and the current detected by the second current detector, between the first self-excited converter and the second self-excited converter. A circulating reactive current detector for detecting a circulating reactive current flowing through
A reference of a circulating reactive voltage that is a reactive voltage between the first self-excited converter and the second self-excited converter so that the circulating reactive current detected by the circulating reactive current detector becomes a target value. A circulation reactive current control unit for calculating a value;
Based on the difference value between the current detected by the first current detector and the current detected by the second current detector, between the first self-excited converter and the second self-excited converter. A circulating effective current detector for detecting a circulating effective current flowing through
A reference of the circulating effective voltage that is an effective voltage between the first self-excited converter and the second self-excited converter so that the circulating effective current detected by the circulating effective current detection unit becomes a target value. A circulating active current control unit for calculating a value;
The first voltage output from the first self-excited converter based on the reference value of the combined invalid voltage, the reference value of the combined effective voltage, the reference value of the circulating invalid voltage, and the reference value of the circulating effective voltage And a reference value conversion unit for calculating a reference value of the second voltage output from the second self-excited converter,
A first gate pulse signal generation unit configured to generate a gate pulse signal for driving the switching element of the first self-excited converter based on a reference value of the first voltage;
2. A second gate pulse signal generation unit configured to generate a gate pulse signal for driving the switching element of the second self-excited converter based on a reference value of the second voltage. Self-excited reactive power compensator. The self-excited reactive power compensator further includes:
A first DC voltage detector for detecting a DC voltage supplied to the first self-excited converter;
A second DC voltage detector for detecting a DC voltage supplied to the second self-excited converter,
The converter controller is
A target value of the combined effective current is calculated so that a combined value of the direct current voltage detected by the first direct current voltage detector and the direct current voltage detected by the second direct current voltage detector becomes a target value. A combined DC voltage controller;
A target value of the circulating effective current is calculated so that a difference value between the DC voltage detected by the first DC voltage detector and the DC voltage detected by the second DC voltage detector becomes a target value. DC voltage balancing control unit,
The combined effective current control unit calculates a reference value of the combined effective voltage so that the combined effective current detected by the combined effective current detecting unit becomes a target value of the combined effective current,
The circulation effective current control unit calculates a reference value of the circulation effective voltage so that the circulation effective current detected by the circulation effective current detection unit becomes a target value of the circulation effective current. Self-excited reactive power compensator.

Images