JP3223304B2 - Power converter control device, self-excited reactive power compensator, and DC power transmission system - Google Patents

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 power converter, and more particularly to a control device for a power converter suitable for controlling a power converter composed of a self-extinguishing type switching element and a control device for the power converter. The present invention relates to a self-excited reactive power compensator and a DC power transmission system used.

[0002]

2. Description of the Related Art Conventionally, in a power system, a power converter has been used as a device for compensating for the reactive power of the system. The power converter has a DC input side connected to a capacitor and an AC output side connected to a power supply system via a transformer. This power converter receives active power from the power supply system, charges the capacitor, converts the output power of the capacitor into AC power, and supplies the converted AC power as reactive power to the power supply system via the transformer. ing.

However, when the transformer is excited by the output current of the power converter, if a DC current flows through the transformer, the core of the transformer is saturated and the back electromotive force is not generated from the transformer. When such a phenomenon occurs, the impedance when the transformer is viewed from the power converter becomes close to zero, and an overcurrent flows through the power converter, which may cause deterioration of a switching element such as a thyristor. Therefore, a method has been proposed in which the DC component of the exciting current flowing through the transformer is detected, and the output current of the power converter is corrected according to the detected value. For example, as described in JP-A-64-5365, the excitation current is integrated over one cycle, and the deviation of the transformer during the positive period and the negative period is calculated based on the deviation between the integral value during the positive period and the integral value during the negative period. There is a type in which a DC component associated with magnetism is detected, and a voltage command value of a power converter is controlled in a direction to reduce a bias current in accordance with the detected value. As described in JP-A-3-93475, a positive current maximum value and a negative current maximum value at which the magnetic flux density of the transformer is almost maximum among the currents supplied to the transformer are respectively sampled. There is a method in which the power converter is held so as to detect the amount of magnetic declination from the deviation of each maximum value, and to suppress the detected amount of demagnetization to zero.

[0004]

However, the prior art employs a configuration in which the output current of the power converter is detected by a current detector and the detected current is integrated for each cycle. In the configuration, the offset amount of the current detector cannot be ignored, and the amount of magnetic polarization cannot be accurately detected. In other words, the current detected by the current detector includes the current obtained by secondary-converting the load current of the transformer and the exciting current, and the ratio of the exciting current to the current obtained by secondary-converting the load current is very large. It is small, about several percent to about 10%. Therefore, even if the detection value of the current detector is integrated over one cycle and the amount of demagnetization is detected from the integrated value, it is difficult to distinguish between the detected value and the offset value between the current detection value and the deviation. It is difficult to detect the magnetic quantity with high accuracy.

In the method of finding the deviation between the positive maximum value and the negative maximum value of the exciting current, if noise or the like is superimposed on the exciting current when any of the maximum values is detected, the deviation of each maximum value becomes large. In addition, even when the demagnetizing current does not flow, there is a possibility that an erroneous detection is made that the demagnetizing current has flowed. In this case, since the power converter is controlled by the erroneous detection signal, a normal operation of suppressing the amount of demagnetization is not performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device for a power converter and a self-excited reactive power which can integrate the exciting current of the exciting current only during the period of occurrence of the magnetizing current and suppress the amount of magnetizing according to the integrated value. A compensating device and a DC power transmission system are provided.

[0007]

In order to achieve the above object, the present invention provides, as a first device, an exciting device for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements. Current detection means, gate pulse generation means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing based on a command for defining an output signal of the power converter, and gate pulse generation means Timing signal generating means for generating a timing signal in response to a positive gate pulse and a negative gate pulse predicted to affect the occurrence of DC bias of a transformer among the gate pulses generated from, and an exciting current detecting means Means for integrating the detected current of each of the timing signals for a certain period from the time of generation of each timing signal, and each integrated value of the integration means for each generation cycle of the gate pulse A deviation calculating means for calculating the deviation, and a gate pulse generated in the next cycle of the gate pulse which has received a gate pulse from the gate pulse generating means and contributed to the calculation operation of the deviation calculating means, which has an effect on the occurrence of DC bias of the transformer. Then, the predicted pulse widths of the positive gate pulse and the negative gate pulse are corrected according to the value calculated by the deviation calculating means, and the other gate pulses are output as they are, and the gate pulse from the gate pulse correcting means is output. Is sequentially applied to each switching element to control the driving of each switching element.

As a second device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing based on a gate pulse generated by the gate pulse generating means. Timing signal generating means for generating a timing signal in response to the predicted positive gate pulse and negative gate pulse, respectively, and the detected current of the exciting current detecting means multiplied by a specified gain only for a certain period from the generation of each timing signal. In other periods, the multiplication means for multiplying the gain by zero and the exciting current multiplied by the gain by the multiplication means are integrated. A dividing means, a deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse, and a gate pulse which receives a gate pulse from the gate pulse generating means and which contributes to the calculation operation of the deviation calculating means. Of the gate pulses generated during the period, the pulse widths of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer are corrected in accordance with the value calculated by the deviation calculating means, and other gate pulses are corrected. Is a control device for a power converter, comprising: a gate pulse correcting means for outputting as it is; and a switching element controlling means for controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correcting means to each switching element. It is what constituted.

As a third device, exciting current detecting means for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing based on a gate pulse generated by the gate pulse generating means. Timing signal generating means for generating a timing signal in response to the predicted positive gate pulse and negative gate pulse, respectively, and the detected current of the exciting current detecting means multiplied by a specified gain only for a certain period from the generation of each timing signal. In other periods, the multiplication means for multiplying the gain by zero and the exciting current multiplied by the gain by the multiplication means are integrated. A positive means which is predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse which has received the gate pulse from the gate pulse generating means and which has contributed to the integration operation of the integrating means. Gate pulse correction means for correcting each pulse width of the gate pulse and the negative gate pulse according to the integration value of the integration means and outputting the other gate pulses as they are, and sequentially applying the gate pulse from the gate pulse correction means to each switching element And a switching device control means for controlling the driving of each switching device.

As a fourth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. Gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at specified timings based on the specified timing, and among the gate pulses generated from the gate pulse generating means, the absolute value of the magnetic flux density of the transformer core is the largest. And a timing signal generating means for generating a timing signal in response to a positive gate pulse and a negative gate pulse generated during the period, and the detection current of the exciting current detecting means is integrated only for a certain period from the generation of each timing signal. Integrating means, deviation calculating means for calculating a deviation of each integrated value of the integrating means for each generation cycle of the gate pulse, The gate pulse generated in the next cycle of the gate pulse which received the gate pulse from the generating means and contributed to the calculation operation of the deviation calculating means is defined as a positive gate pulse and a negative gate pulse predicted to affect the occurrence of DC bias of the transformer. Gate pulse correction means for correcting each pulse width of the gate pulse according to the value calculated by the deviation calculation means and outputting the other gate pulses as they are, and applying the gate pulse from the gate pulse correction means to each switching element sequentially to each switching element. And a switching device control means for controlling the driving of the device.

As a fifth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. Gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at specified timings based on the specified timing, and among the gate pulses generated from the gate pulse generating means, the absolute value of the magnetic flux density of the transformer core is the largest. A timing signal generating means for generating a timing signal in response to each of a positive gate pulse and a negative gate pulse generated during the period, Multiplying means for multiplying the gain and multiplying the gain by zero for the other periods, and the exciting current multiplied by the gain by the multiplying means Integrating means for integrating, deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse, and gate pulse which receives a gate pulse from the gate pulse generating means and contributes to the calculation operation of the deviation calculating means. Of the gate pulses generated in the next cycle, the pulse widths of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer are corrected in accordance with the values calculated by the deviation calculating means, and other values are corrected. The power converter includes a gate pulse correction unit that outputs the gate pulse as it is, and a switching element control unit that controls the driving of each switching element by sequentially applying the gate pulse from the gate pulse correction unit to each switching element. This constitutes a control device.

As a sixth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. Gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at specified timings based on the specified timing, and among the gate pulses generated from the gate pulse generating means, the absolute value of the magnetic flux density of the transformer core is the largest A timing signal generating means for generating a timing signal in response to each of a positive gate pulse and a negative gate pulse generated during the period, Multiplying means for multiplying the gain and multiplying the gain by zero for the other periods, and the exciting current multiplied by the gain by the multiplying means Integrating means for integrating, and gate pulses received in the next cycle of the gate pulse which received the gate pulse from the gate pulse generating means and contributed to the integration operation of the integrating means were predicted to affect the occurrence of DC bias of the transformer. A gate pulse correction unit that corrects each pulse width of the positive gate pulse and the negative gate pulse according to the integration value of the integration unit and outputs other gate pulses as it is, and a gate pulse from the gate pulse correction unit to each switching element. And a switching element control means for controlling driving of each switching element by sequentially applying the switching elements.

As a seventh device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing, and a positive gate generated at the end of the same polarity among the positive and negative gate pulses generated from the gate pulse generating means A timing signal generating means for generating a timing signal in response to the pulse and the negative gate pulse, an integrating means for integrating a detection current of the exciting current detection means only for a certain period from the generation of each timing signal, and a generation cycle of the gate pulse A deviation calculating means for calculating a deviation of each integral value of the integrating means for each of the gate pulses; Each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that contributed to the calculation of the receiving deviation calculating means. Is corrected in accordance with the value calculated by the deviation calculating means, and the other gate pulses are output as they are, and the gate pulse from the gate pulse correcting means is sequentially applied to each switching element to control the driving of each switching element. This constitutes a control device for a power converter including switching element control means.

As an eighth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing, and a positive gate generated at the end of the same polarity among the positive and negative gate pulses generated from the gate pulse generating means A timing signal generating means for generating a timing signal in response to a pulse and a negative gate pulse, and a detection gain of the exciting current detection means multiplied by a specified gain only for a certain period from the time of generation of each timing signal, and to zero for other periods. Multiplication means for multiplying the gain of
An integrating means for integrating the exciting current multiplied by the gain by the multiplying means, a deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse, and a deviation receiving the gate pulse from the gate pulse generating means. The deviation of each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that contributed to the calculation operation of the calculation means. A gate pulse correction unit that corrects according to a value calculated by the calculation unit and outputs other gate pulses as it is, and a switching element that controls driving of each switching element by sequentially applying a gate pulse from the gate pulse correction unit to each switching element. And a control device for a power converter including a control unit.

As a ninth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing, and a positive gate generated at the end of the same polarity among the positive and negative gate pulses generated from the gate pulse generating means A timing signal generating means for generating a timing signal in response to a pulse and a negative gate pulse, and a detection gain of the exciting current detection means multiplied by a designated gain only for a certain period from the time of generation of each timing signal, and to zero for other periods. Multiplication means for multiplying the gain of
An integrating means for integrating the exciting current multiplied by the gain by the multiplying means; and a gate pulse generated in the next cycle of the gate pulse receiving the gate pulse from the gate pulse generating means and contributing to the integration operation of the integrating means. A gate pulse correction unit that corrects each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of the DC bias according to the integration value of the integration unit, and outputs the other gate pulses as they are; A control device for a power converter, comprising: switching element control means for controlling the driving of each switching element by sequentially applying a gate pulse from the correction means to each switching element.

As a tenth device, exciting current detecting means for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing, a voltage pulse detecting means for detecting a voltage pulse applied from the power converter to the transformer, Timing signal generating means for generating a timing signal in response to a positive voltage pulse and a negative voltage pulse predicted to have affected the occurrence of DC bias of the transformer among the detection pulses of the pulse detection means, and an exciting current An integrating means for integrating the detection current of the detecting means only for a certain period from the generation of each timing signal, and an integrating means for each integration cycle of the gate pulse. Deviation calculating means for calculating the deviation of the component value; and a gate pulse generated in the next cycle of the gate pulse which received the gate pulse from the gate pulse generating means and contributed to the calculation operation of the deviation calculating means. A gate pulse correcting unit that corrects each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence in accordance with the value calculated by the deviation calculating unit, and outputs other gate pulses as they are, and a gate pulse correcting unit. And a switching element control means for controlling the driving of each switching element by sequentially applying the gate pulse to each switching element.

As an eleventh device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing, a voltage pulse detecting means for detecting a voltage pulse applied from the power converter to the transformer, Timing signal generating means for generating a timing signal in response to a positive voltage pulse and a negative voltage pulse predicted to have affected the occurrence of DC bias of the transformer among the detection pulses of the pulse detection means, and an exciting current Multiplication that multiplies the detection current of the detection means by a specified gain only for a certain period from the generation of each timing signal, and multiplies by zero gain in other periods A step, an integrating means for integrating the exciting current multiplied by the gain by the multiplying means, a deviation calculating means for calculating a deviation of each integrated value of the integrating means for each generation cycle of the gate pulse, and a gate pulse from the gate pulse generating means. The positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that has contributed to the calculation operation of the deviation calculating means. A gate pulse correction unit that corrects the width in accordance with the value calculated by the deviation calculation unit and outputs other gate pulses as it is, and a gate pulse from the gate pulse correction unit is sequentially applied to each switching element to control the driving of each switching element. And a switching device control means for controlling the power converter.

As a twelfth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing, a voltage pulse detecting means for detecting a voltage pulse applied from the power converter to the transformer, Timing signal generating means for generating a timing signal in response to a positive voltage pulse and a negative voltage pulse predicted to have affected the occurrence of DC bias of the transformer among the detection pulses of the pulse detection means, and an exciting current Multiplication that multiplies the detection current of the detection means by a specified gain only for a certain period from the generation of each timing signal, and multiplies by zero gain in other periods A step, an integrating means for integrating the exciting current multiplied by the gain by the multiplying means, and a gate pulse generated in the next cycle of the gate pulse which has received the gate pulse from the gate pulse generating means and contributed to the integration operation of the integrating means. Gate pulse correcting means for correcting each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer in accordance with the integrated value of the integrating means, and outputting other gate pulses as they are, And a switching element control means for controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correcting means to each switching element.

As a thirteenth device including any one of the first to third devices, the gate pulse correction means includes a means for correcting a pulse width of a positive gate pulse, and an input signal indicating a calculation value. When the polarity of is positive, the operation value is multiplied by the negative gain, and when the polarity of the input signal indicating the operation value is negative, the gain element multiplies the operation value by the positive gain. A pulse width corrector that corrects the pulse width of the gate pulse wide when the polarity of the multiplication value of the receiving gain element is positive, and narrows the pulse width of the gate pulse when the polarity of the multiplication value of the gain element is negative; As a means for correcting the pulse width of the gate pulse, the operation value is multiplied by a positive gain when the polarity of the input signal indicating the operation value is positive, and the negative gain is applied when the polarity of the input signal indicating the operation value is negative. A gain element for multiplying the operation value by the operation value and a gate pulse from the gate pulse generation means, the pulse width of the gate pulse is widened when the polarity of the multiplication value of the gain element is positive, and the polarity of the multiplication value of the gain element is negative. Sometimes, a control device for a power converter includes a pulse width corrector for correcting the pulse width of the gate pulse to be narrow.

As a fourteenth device, exciting current detecting means for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing based on a gate pulse generated by the gate pulse generating means. Timing signal generating means for generating a timing signal in response to the predicted positive gate pulse and negative gate pulse, respectively, and integrating means for integrating the detection current of the exciting current detection means only for a certain period from the time of generation of each timing signal. Deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse; And gate pulse correcting means for outputting the correction in accordance with the calculated value of the deviation calculating means each pulse width of the gate pulse generated in the next cycle of the gate pulse that has contributed to the calculation operation of the deviation calculation means receives a gate pulse from,
A control device for a power converter, comprising: switching element control means for controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correction means to each switching element.

As a fifteenth device, exciting current detecting means for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing based on a gate pulse generated by the gate pulse generating means. Timing signal generating means for generating a timing signal in response to the predicted positive gate pulse and negative gate pulse, respectively, and the detected current of the exciting current detecting means multiplied by a specified gain only for a certain period from the generation of each timing signal. In other periods, the multiplication means for multiplying the gain by zero and the exciting current multiplied by the gain by the multiplication means are integrated. Integrating means, deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse, and a gate pulse which receives a gate pulse from the gate pulse generating means and contributes to the calculation operation of the deviation calculating means. A gate pulse correcting means for correcting and outputting each pulse width of each gate pulse generated in the cycle in accordance with a value calculated by the deviation calculating means; and applying a gate pulse from the gate pulse correcting means to each switching element sequentially to each switching element. And a switching device control means for controlling the driving of the power converter.

As a sixteenth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements, and a command for defining an output signal of the power converter. A gate pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the power converter at a specified timing based on a gate pulse generated by the gate pulse generating means. Timing signal generating means for generating a timing signal in response to the predicted positive gate pulse and negative gate pulse, respectively, and the detected current of the exciting current detecting means multiplied by a specified gain only for a certain period from the generation of each timing signal. In other periods, the multiplication means for multiplying the gain by zero and the exciting current multiplied by the gain by the multiplication means are integrated. Integrating means, and a gate which receives the gate pulse from the gate pulse generating means, corrects each pulse width of each gate pulse generated in the next cycle of the gate pulse which has contributed to the integration operation of the integrating means according to the integrated value of the integrating means, and outputs the corrected signal. A power converter control device comprising: a pulse correction means; and a switching element control means for sequentially applying a gate pulse from the gate pulse correction means to each switching element and controlling the driving of each switching element. is there.

As a seventeenth device, an exciting current detecting means for detecting an exciting current of a transformer connected to a power converter composed of a group of switching elements, and an AC modulated wave corresponding to a voltage command value of the power converter A modulating wave signal generating means for outputting a signal, a modulating wave signal adjusting means for receiving the ac modulating wave signal, adjusting a dc component of the ac modulating wave signal to a specified gain, and outputting the signal, and an output signal of the modulating wave signal adjusting means Pulse signal generating means for sequentially generating positive and negative gate pulses according to the comparison result and the amplitude of the carrier signal, and among the gate pulses generated from the gate pulse generating means, the influence of the DC bias on the transformer. Then, a timing signal generating means for generating a timing signal in response to the predicted positive gate pulse and the predicted negative gate pulse, respectively, and a detection current of the excitation current detection means. An integrating means for integrating only a certain period from the time of the timing signal generator, a deviation calculating means for calculating a deviation of each integral value of the integrating means at every generation cycle of the gate pulse,
Driving the switching elements by sequentially applying a gate pulse from the gate pulse generating means to each switching element, and a gain specifying means for specifying a gain in accordance with the value calculated by the deviation calculating means for the modulated wave signal adjusting means; And a switching device control means for controlling the power converter.

As an eighteenth device, a transformer connected to a power supply system, a power converter connected to the power supply system via the transformer, and a capacitor connected to a DC input side of the power converter are provided. In the self-excited reactive power compensating device comprising: a self-excited reactive power compensating device using any one of the first to eighteenth devices as a device for controlling the driving of the switching element group constituting the power converter. This constitutes a reactive power compensator.

As a nineteenth device, a power converter connected to a power supply system via a transformer and a power converter connected to a load via a transformer are connected via a DC transmission line. In the DC power transmission system, a DC power transmission system using any one of the first to seventeenth devices as a device for controlling the driving of the switching element group forming the power converter. It is.

[0026]

According to the above-mentioned means, when a command for defining the output signal of the power converter is generated, a positive / negative gate pulse is supplied to each switching element of the power converter at a designated timing based on the command. It is applied sequentially. When each switching element is on / off controlled by the gate pulse, the output voltage of the power converter is controlled according to the gate pulse, and the transformer is excited by the output current of the power converter. At this time, the primary current and secondary current of the transformer are detected,
Only the exciting current can be detected from the difference between the ampere turn of the primary current and the ampere turn of the secondary current. Then, the generation of a gate pulse is monitored, and a timing signal is generated in response to a positive gate pulse and a negative gate pulse that are predicted to affect the occurrence of DC bias of the transformer among the gate pulses. If the timing signal is generated twice when the positive and negative gate pulses are generated over one cycle, the exciting current is integrated only for a certain period from the generation of each timing signal. Then, the deviation of the integral value of each excitation current is obtained as the amount of magnetization. When the amount of magnetization is calculated, the pulse widths of the positive gate pulse and the negative gate pulse, which are predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle, are determined according to the amount of magnetization. The correction is performed, and the other gate pulses are output as they are. For example, when the amount of magnetization increases in the positive direction, the pulse width of the gate pulse is adjusted so that the DC component of the voltage becomes negative. Conversely, when the amount of magnetization increases in the negative direction, the DC component of the voltage increases. The pulse width of the gate pulse is adjusted to be positive. As described above, by adjusting the DC component of the voltage, it is possible to suppress the bias current from flowing through the transformer.

[0027]

An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the power converter is applied to a self-excited var compensator, and the specific configuration of the controller is shown in FIG.
FIG. 2 shows the waveform of each part of the control device, and FIG. 3 shows the entire configuration of the self-excited var compensator. FIG.
In the self-excited var compensator, the capacitor 10,
Power converters 12, 14, 16, 18 and transformers 20, 2
2, 24, 26, etc., and each transformer 20, 2,
The primary sides of 2, 24 and 26 are connected to a power supply system 30 via a circuit breaker 28. The capacitor 10 is connected to the DC input side of each of the power converters 12, 14, 16, 18 and the AC output side of each of the power converters 12, 14, 16, 18 is connected to each of the transformers 20, 22, 24, 26. Is connected to the secondary side. Each of the power converters 12, 14, 16, and 18 includes a thyristor that is a self-extinguishing type switching element. When each of the switching elements is turned on / off by a gate pulse from the control device 32, each of the power converters 12, 14, 16, and 18 receives power. Depending on the magnitude of the output voltage of the converters 12, 14, 16, and 18, reactive power can be supplied to the power supply system 30 or can be absorbed from the power supply system 30. The capacitor 10 is charged and discharged with the power supply system 30 via the power converters 12 to 18 and the transformers 20 to 26 so that the terminal voltage is maintained at a constant voltage.

The control device 32 includes current detectors 34, 36, 3
8, 40, 42, voltage detector 44, reactive power control circuit 4
6, a pulse generation circuit 48 and a demagnetization suppression control circuit 50. The primary current, the primary voltage, the secondary current, the voltage across the capacitor 10 and the reactive power command of the transformers 20 to 26 are provided. The output power of each of the power converters 12 to 18 can be controlled based on Q. Therefore, each transformer 2
Current detectors 34, 36, 38, and 40 for detecting the current on the secondary side are provided on the secondary side of the transformers 0 to 26, and the current detector 42 and the voltage detector are provided on the primary side of the transformers 20 to 26. Detector 4
4 are provided. The detection currents of the current detectors 34 to 42 are input to the demagnetization suppression control circuit 50, and the detection current of the current detector 42 and the detection voltage of the voltage detector 44 are input to the reactive power control circuit 46. Reactive power control circuit 4
6 is a command for defining the output voltage of each of the power converters 12 to 18 based on the detection current of the current detector 42, the detection voltage of the voltage detector 44, the terminal voltage of the capacitor 10, and the reactive power command Q, A phase difference command φ indicating the phase difference between the modulation rate command K and the system voltage is output to the pulse generation circuit 48. The pulse generating circuit 48 sequentially generates positive and negative gate pulses for each switching element at specified timings based on the modulation rate command K and the phase difference command φ, and uses the generated gate pulse as a reference gate pulse as a demagnetization suppression control circuit 50. And a signal relating to the switching angle θp1 defining the output timing of the positive gate pulse and the switching angle θn1 defining the generation timing of the negative gate pulse are output to the demagnetization suppression control circuit 50. Further, a signal relating to the switching angles θp2 and θn2 is received from the demagnetization suppression control circuit 50, a reference gate pulse is corrected according to the signal, and the corrected gate pulse is output to each switching element of each of the power converters 12 to 18. Has become. That is, the pulse generation circuit 48 constitutes a gate pulse generation means and a switching element control means.

As shown in FIG. 1, the magnetization suppression control circuit 50 includes an excitation current detector 52, a phase detector 54, a gain adjuster 56, a reset signal generator 58, a sample and hold signal generator 60, a multiplier 62, 64, reset integrators 66 and 68, an adder 70, a sample holder 72, gain elements 74 and 76, and adders 78 and 80.

The excitation current detector 52 is connected to each of the current detectors 34.
40 and the detected current i1 of the current detector 42.
, And is configured as exciting current detecting means for detecting only the exciting current i0 from the difference between the ampere turns of the primary current i1 and the secondary current i2 of each of the transformers 20 to 26. That is, the secondary conversion current i1 'of the exciting current i0 and the primary current i0 flows on the secondary side of each of the transformers 20 to 26 (i2 = i
0 + i1 ′), i1 ′ is subtracted from the current i2, so that only the exciting current i0 can be obtained. This exciting current i0 is obtained by integrating this voltage when a voltage waveform V as shown in FIG. 2A is applied to the windings of the transformers 20 to 26 as shown in FIG. And a waveform similar to the waveform of the applied magnetic flux density B. This exciting current is
When the magnetic flux is generated in any of the transformers, the magnetic flux density B becomes excessively large at the first portion where the peak value is obtained, and the current waveform becomes as shown in FIG. The exciting current i0 is divided into two systems and input to resetting integrators 66 and 68 via multipliers 62 and 64. Each of the multipliers 62 and 64 receives the pulse signal Pk from the gain controller 56.
The excitation current i0 is multiplied according to p and Pkn, and the multiplied signal is output to the integrators 66 and 68. The timing of the pulse output from the gain adjuster 56 is determined by the detection signal from the phase detector 54. It is controlled.

The phase detector 54 detects the phase of the gate pulse generated from the pulse generator 48, and outputs a detection output to the gain controller 56, the reset signal generator 58, and the sample and hold signal generator 60. ing. The pulse generation circuit 48 outputs two positive gate pulses and two negative gate pulses between 0 degree and 360 degrees, and the phase according to the generation timing of each gate pulse is adjusted by gain. The signal is input to the device 56. The gain adjuster 56 is connected to the phase detector 5
4, the pulse signals Pkp and Pkn are output to the multipliers 62 and 64. That is,
The phase detector 54 and the gain adjuster 56 are configured as timing signal generating means, and the gate pulses P1 to P1
0, the timing t in response to the positive gate pulses P2, P6, P10 and the negative gate pulses P4, P8 predicted to affect the occurrence of the DC bias of the transformers 20 to 26.
At 1, t3, t5, t7 and t9, pulse signals Pkp and Pkn are output as timing signals. The generation timing of these pulses is such that when a positive gate pulse and a negative gate pulse are output continuously, respectively, the magnetic field is demagnetized in response to the last positive or negative gate pulse that occurs in each cycle. The setting is made in consideration of the occurrence of current. This timing corresponds to the timing at which the absolute value of the magnetic flux density of the iron core of each of the transformers 20 to 26 becomes maximum. Gain adjuster 56
Output pulse signals Pkp and Pkn whose gains have been adjusted are input to the integrators 66 and 68 only during a certain period of time, and to zero in other periods. Is input to the integrators 66 and 68. Each of the integrators 66 and 68 corresponds to (f) in FIG.
As shown in (g) and (h), the output signals of the multipliers 62 and 64 are integrated until the reset signals R1 and R2 are output from the reset signal generator 58, and the respective integrated values Sp and Sn are integrated.
Is output to the adder 70. The adder 70 is configured as a deviation calculating unit that adds the positive integral value Sp and the negative integral value Sn to calculate a deviation ΔS between the two. As shown in FIG. 2C, Δs is obtained as a signal corresponding to the difference between the area of the positive-side hatched portion and the area of the negative-side hatched portion of the exciting current i0, and is input to the sample holder 72. Is done. Sample holder 72
Is configured to sample and hold the output signal of the adder 70 in response to a hold signal H1 generated near the time when the integral value Sn indicates the final value, and output the difference signal ΔSh to the gain elements 74 and 76.

The gain elements 74 and 76 multiply the difference signal ΔSh by a gain corresponding to the polarity and magnitude of the difference signal ΔSh to generate a signal relating to a correction width Δθp for correcting the pulse width of the gate pulse. It is configured.
The gain element 74 multiplies the negative gain when the polarity of the difference signal ΔSh is positive, and multiplies the positive gain when the polarity of the difference signal ΔSh is negative. The gain element 76 sets the positive gain when the polarity of the difference signal ΔSh is positive. Is configured to multiply the difference signal ΔSh by a negative gain when is negative. The gain element 74 outputs a signal relating to the correction width Δθp for correcting the pulse width of the positive gate pulse, and the gain element 76 outputs a signal relating to the correction width Δθn for correcting the pulse width of the negative gate pulse. These signals are output to the adders 78 and 80, respectively. Signals relating to the switching angles θp1 and θn1 are input from the pulse generation circuit 48 to the adders 78 and 80, respectively. The adders 78 and 80 provide the switching angles θp1 and θn1 and the correction widths Δθp and Δθn, respectively.
And the switching angles θp2, θn2
Is output to the pulse generation circuit 48. This switching angle θp2 has a correction width Δθ
When p is positive, the pulse width of the gate pulse is widened, and when negative, the pulse width of the gate pulse is corrected to be narrow. The switching angle θn2 is determined by the pulse width of the gate pulse when the polarity of the correction width Δθn is positive. Is widened, and when negative, the pulse width of the gate pulse is corrected to be narrow. That is, each adder 78,
Numeral 80 is configured as a pulse width corrector, and gain elements 74 and 76 and adders 78 and 80 are each configured as gate pulse correcting means. In the case of the present embodiment, of the gate pulses P1 to P10, the gate pulse P
Only the pulse widths of P2, P4, P6, P8, and P10 are corrected, and the other gate pulses are output as they are.

In the above configuration, the reactive power control circuit 4
When the reactive power command Q is input to 6, a gate pulse based on the reactive power command is applied to each thyristor of each of the power converters 12 to 18. When gate pulses P1 to P10 as shown in FIG. 2A are sequentially applied to each thyristor, a voltage having a waveform corresponding to each gate pulse is applied to each winding of each of the transformers 20 to 26. . At this time, an exciting current i0 according to the gate pulse flows through each transformer.
The exciting current i0 is detected by the exciting current detector 52, and the detected exciting current i0 is input to the multipliers 62 and 64. On the other hand, in response to the generation of the gate pulse, timings t1, t3, t5, t7,
At t9, pulse signals Pkp and Pkn are sequentially output. When the multipliers 62 and 64 multiply the exciting current i0 by the pulse signal in response to the pulse signals Pkp and Pkn, the multiplied values are input to the integrators 66 and 68, respectively. When the multiplied values are integrated by the integrators 66 and 68, the integrated values Sp and Sn are held until the reset signal R1 is generated, and these integrated values are added by the adder 70. When the respective integrated values are added by the adder 70, a deviation ΔS of each integrated value is obtained. The deviation ΔS is obtained as a signal corresponding to the difference between the area of the positive side hatched portion and the area of the negative side hatched portion of the exciting current i0. And the gate pulse P
When the deviation ΔS is sampled and held by the sample holder 72 when any of the transformers generates a demagnetizing current in response to step 2, the difference signal Δh corresponding to the positive amplitude h is obtained. The difference signal ΔSh is applied to gain elements 74 and 76, respectively.
, The difference signal ΔSh is multiplied by a gain corresponding to the polarity and the level of the difference signal ΔSh, and correction widths Δθp and Δθn corresponding to the multiplied value are obtained. In this case, a correction width Δθp of the negative polarity and a correction width Δθn of the positive polarity are obtained,
Each switching angle θp is obtained by the signals of these correction widths.
1, θn1 is corrected. That is, the gate pulse P2
Is corrected when the gate pulse P6 corresponding to the gate pulse P6 is generated, and the pulse width of the gate pulse P8 is widened when the gate pulse P8 corresponding to the gate pulse P4 is generated. Correction is performed. Thus, when the magnetizing current flows through the transformer in response to the positive gate pulse, the pulse width of the positive gate pulse among the gate pulses generated in the next cycle is reduced, and the pulse width of the negative gate pulse is reduced. Is widened to suppress the imbalance between the positive component and the negative component of the exciting current, so that the occurrence of the demagnetizing current can be suppressed. In this case, the exciting current i0 of only the exciting current generation period of the exciting current i0 is integrated, and the occurrence of the exciting current is suppressed according to the integrated value. Without consideration, and even when noise is superimposed on the exciting current, it is possible to reliably detect the amount of magnetic transformation accompanying the DC bias of the transformer.

Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the exciting current detector 52
The variable gain integrator 82 is provided between the adder 62 and the sample holder 72. The pulse signal Pk in response to the gate pulses P2 and P4 is sequentially input from the gain adjuster 56 to the adder 62. When the multiplied value obtained by multiplying each pulse signal Pk by the exciting current i0 is integrated by the variable gain integrator 82, a signal corresponding to the deviation of each integrated value is input to the sample holder 72. For this reason, in the present embodiment, the output side of the exciting current detector 52 can be a single system, and the adder 70 can be omitted.

Next, a third embodiment of the present invention will be described with reference to FIGS. In this embodiment, the sample holder 7 is used.
The output side of No. 2 is divided into four systems according to the number of gate pulses. A gain element 84 and an adder 88 are added to correct the positive gate pulse, and correct the pulse width of the negative gate pulse. Element 86 and adder 9
0 has been added. Also, from the pulse generation circuit 48,
The signal related to the switching angle θp2 defining the generation timing of the first gate pulse among the positive gate pulses and the signal related to the switching angle θn2 defining the generation timing of the first gate pulse among the negative gate pulses are added to the adder 88, respectively. The data is input to the device 90. The gain element 84 has a characteristic reverse to that of the gain element 74, and the gain element 86 has a characteristic reverse to that of the gain element 76. The gain of each of the gain elements 74, 76, 84, 86 is set to の of the gain elements 74, 76 shown in FIG. Then, as shown in FIG. 2, the gate pulse P2
When the DC bias is generated in the transformer in response to the difference signal ΔSh from the sample holder 72, each gain element 7
4,76,84,86, and each correction width Δ
θp1, Δθp2, Δθn1, and Δθn2 are added to adders 78, 88, 80, and 90, respectively. Then, the angles of the switching angles θp2 and θn1 are corrected to be large, and the angles of the switching angles θp1 and θn2 are corrected to be small. Therefore, of the gate pulses generated in the next cycle, the pulse width of the gate pulse P5 is narrow, and the gate pulse P6
Are corrected to be narrow, and the pulse widths of the gate pulses P7 and P8 are respectively widened. In the present embodiment, the correction width of the pulse width for each of the gate pulses P5, P6, P7, and P8 is smaller than that of the first embodiment, but the pulse width of all the gate pulses is corrected. As a whole, the imbalance between the positive and negative parts of the exciting current can be suppressed.

In this embodiment, each gate pulse P5, P5
When correcting the pulse widths of P6, P7 and P8, FIG.
The pulse width is corrected to a symmetrical pulse width based on the positive peak value or the negative peak value of the fundamental wave voltage indicated by the dashed line. Therefore, the phase change of the fundamental wave voltage due to the correction can be made theoretically zero.

In each of the above embodiments, the case where the gate pulse is generated from the pulse generation circuit 48 in accordance with the modulation rate command K and the phase difference command φ has been described, but as shown in FIG. A gate pulse can be generated by a control method. The gate pulse generator to which this method is applied includes a sine wave generation circuit 92,
Carrier generation circuit 94, gain adjustment circuit 96, adder 9
8. It comprises a comparator 100. The sine wave generating circuit 92 outputs an AC modulated wave signal according to the voltage command V to the adder 98. The signal of the gain Δe that specifies the gain of the DC component is input from the gain adjustment circuit 96 to the adder 98. The difference signal ΔSh from the sample holder 72 is input to the gain adjustment circuit 96, and the gain adjustment circuit 96 is configured as a gain designating unit that designates a gain Δe according to the difference signal ΔSh. The gain Δe is set to zero when no DC bias occurs in the transformer, and is set to a positive or negative value according to the value of the bias current when a bias current flows through the transformer. It has become. The AC modulated wave signal added by the adder 98 is input to the comparator 100. The carrier signal from the carrier generation circuit 94 is input to the comparator 100, the amplitude of the AC modulated wave signal is compared with the amplitude of the carrier signal, and a gate pulse according to the comparison result is output from the comparator 100. ing. in this case,
When DC bias occurs in the transformer due to the gate pulse,
The difference signal ΔSh corresponding to the magnitude of the bias current is input to the gain adjustment circuit 96, the gain Δe is set according to the magnitude and the polarity of the bias current, and the DC component of the AC modulated wave signal becomes positive or negative. The shift is performed and the pulse width of each gate pulse is adjusted.

Next, a fifth embodiment of the present invention will be described with reference to FIG. This embodiment is one in which the power converter is applied to a DC power transmission system. (A) and (b) show embodiments in which voltage-type power converters 200 to 222 are used at both ends of a DC transmission line. (C) shows an embodiment using current-type power converters 224 to 230 at both ends of a DC transmission line. Each of the power converters 200 to 230 is connected to a load or an AC power supply via transformers 1001 to 1010.

In each DC power transmission system, transformers 1001 to 1010 are used in order to reduce harmonics by performing multiplex operation while shifting the operation phase difference for each unit converter. In such a DC power transmission system, since the DC voltage is often used at a high level, each transformer is often used in a severe condition, and a highly accurate control of demagnetization is required. Therefore, even when controlling the power converter used in such a system, if the control device used in each of the above embodiments is used, the detection accuracy of the amount of demagnetization becomes high, so that high-precision demagnetization suppression control can be performed. It becomes possible.

Each of the above embodiments can be realized by software processing using a microcomputer. In this case, the hardware for the demagnetization suppression control becomes unnecessary.

[0041]

As described above, according to the present invention,
The exciting current of the exciting current only during the period of occurrence of the magnetizing current is integrated, and the amount of magnetizing is suppressed according to the integrated value, so that noise is superimposed on the exciting current without being affected by the offset of the current detecting means. Even so, the magnetizing current can be detected with high accuracy, and the magnetizing of the transformer can be effectively suppressed. Therefore, the overcurrent due to the magnetic bias can be suppressed, so that the semiconductor switching element used in the power converter can be protected from the overcurrent, and the density of the magnetic flux of the iron core of the transformer is increased to reduce the size and weight of the transformer. It can contribute to the conversion.

[Brief description of the drawings]

FIG. 1 is a specific configuration diagram of a control device according to a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the first embodiment.

FIG. 3 is an overall configuration diagram of a self-excited var compensator.

FIG. 4 is a main part configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a waveform chart for explaining the operation of FIG. 4;

FIG. 6 is a main part configuration diagram showing a third embodiment of the present invention.

FIG. 7 is a waveform chart for explaining the operation of FIG. 6;

FIG. 8 is a main part configuration diagram showing a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram of a DC power transmission system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Capacitor 12, 14, 16, 18 Power converter 20, 22, 24, 26 Transformer 30 Power supply system 32 Control device 34, 36, 38, 40, 42 Current detector 46 Reactive power control circuit 48 Pulse generation circuit 50 Polarization Magnetic suppression control circuit 52 Excitation current detector 54 Phase detector 56 Gain adjuster 58 Reset signal generator 60 Sample hold signal generator 62, 64 Multiplier 66, 68 Integrator with reset 70 Adder 72 Sample holder 74, 76 Gain Element 78, 80 Adder

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeta Ueda 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. Inside the research laboratory (72) Inventor Hidetoshi Aizawa 3-1-1, Sakaimachi, Hitachi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (56) References JP-A-64-5365 (JP, A) JP-A-5-305453 (JP, A) JP-A-4-359680 (JP, A) JP-A-3-103076 (JP, A) JP-A-2-155436 (JP, A) JP-A-1-171591 (JP, U) ( 58) Surveyed field (Int.Cl. ⁷ , DB name) H02M ⁷ /42-7/98

Claims (19)

(57) [Claims] An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, and positive gate pulses generated from the gate pulse generating means which are predicted to affect the occurrence of DC bias of the transformer. A timing signal generating means for generating a timing signal in response to each of the gate pulse and the negative gate pulse; an integrating means for integrating the detection current of the exciting current detection means only for a certain period from the generation of each timing signal; A deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle; and a gate pulse from the gate pulse generating means. Each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that contributed to the calculation of the receiving deviation calculating means. Is corrected in accordance with the value calculated by the deviation calculating means, and the other gate pulses are output as they are, and the gate pulse from the gate pulse correcting means is sequentially applied to each switching element to control the driving of each switching element. A control device for a power converter, comprising: a switching element control unit. 2. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, and positive gate pulses generated from the gate pulse generating means which are predicted to affect the occurrence of DC bias of the transformer. Signal generating means for generating a timing signal in response to each of the gate pulse and the negative gate pulse, and the detection current of the exciting current detection means is multiplied by a specified gain only for a certain period from the generation of each timing signal for other periods. Is multiplication means for multiplying by zero gain,
An integrating means for integrating the exciting current multiplied by the gain by the multiplying means, a deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse, and a deviation receiving the gate pulse from the gate pulse generating means. The deviation of each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that contributed to the calculation operation of the calculation means. A gate pulse correction unit that corrects according to a value calculated by the calculation unit and outputs other gate pulses as it is, and a switching element that controls driving of each switching element by sequentially applying a gate pulse from the gate pulse correction unit to each switching element. A control device for a power converter, comprising: a control unit. 3. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, and positive gate pulses generated from the gate pulse generating means which are predicted to affect the occurrence of DC bias of the transformer. Signal generating means for generating a timing signal in response to each of the gate pulse and the negative gate pulse, and the detection current of the exciting current detection means is multiplied by a specified gain only for a certain period from the generation of each timing signal for other periods. Is multiplication means for multiplying by zero gain,
An integrating means for integrating the exciting current multiplied by the gain by the multiplying means; and a gate pulse generated in the next cycle of the gate pulse receiving the gate pulse from the gate pulse generating means and contributing to the integration operation of the integrating means. A gate pulse correction unit that corrects each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of the DC bias according to the integration value of the integration unit, and outputs the other gate pulses as they are; A switching element control means for sequentially applying a gate pulse from the correction means to each switching element to control the driving of each switching element. 4. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a designated timing, and a period in which the absolute value of the magnetic flux density of the transformer core becomes maximum among the gate pulses generated from the gate pulse generating means. Timing signal generating means for respectively generating a timing signal in response to the generated positive gate pulse and negative gate pulse, integration means for integrating the detection current of the exciting current detection means only for a certain period from the time of generation of each timing signal, A deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse; Of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that received the pulse and contributed to the calculation operation of the deviation calculating means. A gate pulse correction unit that corrects the pulse width according to the value calculated by the deviation calculation unit and outputs other gate pulses as it is, and a gate pulse from the gate pulse correction unit is sequentially applied to each switching element to drive each switching element. A control device for a power converter, comprising: a switching element control unit for controlling. 5. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a designated timing, and a period in which the absolute value of the magnetic flux density of the transformer core becomes maximum among the gate pulses generated from the gate pulse generating means. A timing signal generating means for generating a timing signal in response to the generated positive gate pulse and negative gate pulse, respectively, and a detection gain of the exciting current detection means multiplied by a designated gain only for a certain period from the time of generation of each timing signal. In other periods, multiplication means for multiplying the gain by zero and integration means for integrating the exciting current multiplied by the gain by the multiplication means A deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle of the gate pulse; and a gate pulse received from the gate pulse generating means, and a next cycle of the gate pulse which has contributed to the calculation operation of the deviation calculating means. Among the generated gate pulses, the pulse widths of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer are corrected in accordance with the value calculated by the deviation calculating means, and the other gate pulses are left as they are. A control device for a power converter, comprising: a gate pulse correcting means for outputting; and a switching element control means for controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correcting means to each switching element. 6. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a designated timing, and a period in which the absolute value of the magnetic flux density of the transformer core becomes maximum among the gate pulses generated from the gate pulse generating means. A timing signal generating means for generating a timing signal in response to the generated positive gate pulse and negative gate pulse, respectively, and a detection gain of the exciting current detection means multiplied by a designated gain only for a certain period from the time of generation of each timing signal. In other periods, multiplication means for multiplying the gain by zero and integration means for integrating the exciting current multiplied by the gain by the multiplication means And a positive gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that received the gate pulse from the gate pulse generating means and contributed to the integration operation of the integrating means Gate pulse correction means for correcting each pulse width of the negative gate pulse according to the integration value of the integration means and outputting the other gate pulses as they are, and applying the gate pulse from the gate pulse correction means to each switching element sequentially. A control device for a power converter, comprising: switching element control means for controlling driving of each switching element. 7. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the switch at a specified timing, and a positive and negative gate pulse generated at the end of the same polarity among positive and negative gate pulses generated from the gate pulse generating means. Timing signal generating means for respectively generating a timing signal in response to a gate pulse, integrating means for integrating the detection current of the exciting current detecting means only for a certain period from generation of each timing signal, and integrating means for each generation cycle of the gate pulse Deviation calculating means for calculating a deviation of each integrated value of the above, and deviation calculating means receiving a gate pulse from the gate pulse generating means Deviation calculating means for calculating the pulse width of each of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse contributing to the calculation of And a switching element control means for controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correction means to each switching element and outputting the other gate pulses as they are. A control device for a power converter, comprising: 8. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the switch at a specified timing, and a positive and negative gate pulse generated at the end of the same polarity among positive and negative gate pulses generated from the gate pulse generating means. A timing signal generating means for generating a timing signal in response to a gate pulse, and a detection current of the excitation current detecting means are multiplied by a specified gain only for a certain period from the timing of generation of each timing signal, and multiplied by a zero gain during other periods. Multiplying means, an integrating means for integrating the exciting current multiplied by the gain by the multiplying means, and a gate pulse generation period. A deviation calculating means for calculating a deviation of each integral value of the integrating means, and a voltage change of a gate pulse generated in the next cycle of the gate pulse which has received a gate pulse from the gate pulse generating means and contributed to the calculation operation of the deviation calculating means. A gate pulse correcting unit that corrects each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of the DC bias of the device according to the value calculated by the deviation calculating unit, and outputs the other gate pulses as they are. And a switching element control means for sequentially applying a gate pulse from the gate pulse correction means to each switching element to control the driving of each switching element. 9. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the switch at a specified timing, and a positive and negative gate pulse generated at the end of the same polarity among positive and negative gate pulses generated from the gate pulse generating means. A timing signal generating means for generating a timing signal in response to a gate pulse, and a detection current of the excitation current detecting means are multiplied by a specified gain only for a certain period from the timing of generation of each timing signal, and multiplied by a zero gain during other periods. Multiplication means, integration means for integrating the exciting current multiplied by the gain by the multiplication means, and gate pulse generation means. Of the positive and negative gate pulses predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse that received the gate pulse and contributed to the integration operation of the integration means. Gate pulse correction means for correcting each pulse width according to the integration value of the integration means and outputting the other gate pulses as they are, and driving each switching element by sequentially applying a gate pulse from the gate pulse correction means to each switching element. A control device for a power converter, comprising: a switching element control unit for controlling. 10. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, voltage pulse detecting means for detecting a voltage pulse applied from a power converter to a transformer, and voltage pulse detecting means. Timing signal generating means for generating a timing signal in response to a positive voltage pulse and a negative voltage pulse predicted to have influenced the occurrence of DC bias of the transformer among the detection pulses, and detection of the exciting current detecting means Integrator that integrates current only for a certain period of time after each timing signal is generated, and deviation of each integrated value of integrator is calculated every gate pulse generation cycle The deviation calculating means, and the gate pulse generated in the next cycle of the gate pulse which has received the gate pulse from the gate pulse generating means and contributed to the calculation operation of the deviation calculating means is expected to affect the occurrence of DC bias of the transformer. Gate pulse correction means for correcting the respective pulse widths of the positive gate pulse and the negative gate pulse in accordance with the value calculated by the deviation calculation means, and outputting the other gate pulses as they are, and switching the gate pulse from the gate pulse correction means for each switching. A switching element control means for controlling the driving of each switching element by sequentially applying the switching elements to the elements. 11. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse pulse generating means for sequentially generating positive and negative gate pulses for each switching element of a transformer at a specified timing, voltage pulse detecting means for detecting a voltage pulse applied from a power converter to a transformer, and voltage pulse detecting means. Timing signal generating means for generating a timing signal in response to a positive voltage pulse and a negative voltage pulse predicted to have influenced the occurrence of DC bias of the transformer among the detection pulses, and detection of the exciting current detecting means Multiplying means that multiplies the current by a specified gain only for a certain period from the time of generation of each timing signal and multiplies by zero gain in other periods, Integrating means for integrating the exciting current multiplied by the gain, deviation calculating means for calculating a deviation of each integrated value of the integrating means for each generation cycle of the gate pulse, and deviation calculating means for receiving the gate pulse from the gate pulse generating means Deviation calculating means for calculating the pulse width of each of the positive gate pulse and the negative gate pulse predicted to affect the occurrence of DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse contributing to the calculation of And a switching element control means for controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correction means to each switching element and outputting the other gate pulses as they are. A control device for a power converter, comprising: 12. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter constituted by a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, voltage pulse detecting means for detecting a voltage pulse applied from a power converter to a transformer, and voltage pulse detecting means. Timing signal generating means for generating a timing signal in response to a positive voltage pulse and a negative voltage pulse predicted to have influenced the occurrence of DC bias of the transformer among the detection pulses, and detection of the exciting current detecting means Multiplying means that multiplies the current by a specified gain only for a certain period from the time of generation of each timing signal and multiplies by zero gain in other periods, An integrating means for integrating the exciting current multiplied by the gain, and a DC bias of the transformer among the gate pulses generated in the next cycle of the gate pulse receiving the gate pulse from the gate pulse generating means and contributing to the integration operation of the integrating means. A gate pulse correction unit that corrects each pulse width of the positive gate pulse and the negative gate pulse predicted to affect the generation of magnetism according to the integration value of the integration unit, and outputs other gate pulses as they are, and a gate pulse correction unit And a switching element control means for controlling the driving of each switching element by sequentially applying the gate pulse from the switching element to each switching element. 13. The gate pulse correcting means, as means for correcting the pulse width of a positive gate pulse, multiplies the calculated value by a negative gain when the polarity of an input signal indicating the calculated value is positive, and calculates the calculated value. When the polarity of the input signal shown is negative, a gain element for multiplying the operation value by a positive gain when the polarity of the input signal is negative, and the pulse width of the gate pulse is widened when the polarity of the multiplied value of the gain element is positive when the gate pulse is received from the gate pulse generation means. A pulse width corrector for correcting the pulse width of the gate pulse to be narrower when the polarity of the multiplied value of the gain element is negative, and as a means for correcting the pulse width of the negative gate pulse, the polarity of the input signal indicating the operation value is provided. A gain element that multiplies the operation value by a positive gain when is positive, and a gain element that multiplies the operation value by a negative gain when the polarity of the input signal indicating the operation value is negative; A pulse width corrector that corrects the pulse width of the gate pulse when the polarity of the multiplied value of the gain element is positive, and narrows the pulse width of the gate pulse when the polarity of the multiplied value of the gain element is negative. The control device for a power converter according to any one of claims 1 to 12, wherein: 14. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, and positive gate pulses generated from the gate pulse generating means which are predicted to affect the occurrence of DC bias of the transformer. A timing signal generating means for generating a timing signal in response to each of the gate pulse and the negative gate pulse; an integrating means for integrating the detection current of the exciting current detection means only for a certain period from the generation of each timing signal; A deviation calculating means for calculating a deviation of each integral value of the integrating means for each generation cycle; and a gate pulse from the gate pulse generating means. Gate pulse correcting means for receiving and correcting each pulse width of each gate pulse generated in the next cycle of the gate pulse contributing to the calculation operation of the deviation calculating means in accordance with the value calculated by the deviation calculating means; And a switching element control means for controlling the driving of each switching element by sequentially applying the gate pulse from the switching element to each switching element. 15. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, and positive gate pulses generated from the gate pulse generating means which are predicted to affect the occurrence of DC bias of the transformer. Signal generating means for generating a timing signal in response to each of the gate pulse and the negative gate pulse, and the detection current of the exciting current detection means is multiplied by a specified gain only for a certain period from the generation of each timing signal for other periods. Is multiplication means for multiplying the gain by zero, integration means for integrating the exciting current multiplied by the gain by the multiplication means, Deviation calculating means for calculating the deviation of each integral value of the integrating means for each pulse generation cycle; and each of the gate pulses generated in the next cycle of the gate pulse which has received a gate pulse from the gate pulse generation means and contributed to the calculation operation of the deviation calculation means. A gate pulse correcting means for correcting and outputting each pulse width of the gate pulse according to a value calculated by the deviation calculating means, and controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correcting means to each switching element. A control device for a power converter, comprising: a switching element control unit. 16. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and power conversion based on a command for defining an output signal of the power converter. Pulse generating means for sequentially generating positive and negative gate pulses for each switching element of the transformer at a specified timing, and positive gate pulses generated from the gate pulse generating means which are predicted to affect the occurrence of DC bias of the transformer. Signal generating means for generating a timing signal in response to each of the gate pulse and the negative gate pulse, and the detection current of the exciting current detection means is multiplied by a specified gain only for a certain period from the generation of each timing signal for other periods. Is multiplication means for multiplying the gain by zero, integration means for integrating the exciting current multiplied by the gain by the multiplication means, Gate pulse correction means for receiving the gate pulse from the pulse generation means, correcting each pulse width of each gate pulse generated in the next cycle of the gate pulse contributing to the integration operation of the integration means in accordance with the integration value of the integration means, and outputting the corrected pulse width; A control device for a power converter, comprising: switching element control means for controlling the driving of each switching element by sequentially applying a gate pulse from the gate pulse correction means to each switching element. 17. An exciting current detecting means for detecting an exciting current of a transformer connected to a power converter comprising a group of switching elements, and outputting an AC modulated wave signal corresponding to a voltage command value of the power converter. A modulating wave signal generating means, a modulating wave signal adjusting means for receiving an ac modulating wave signal, adjusting a dc component of the ac modulating wave signal to a specified gain, and outputting the adjusted gain, and an output signal of the modulating wave signal adjusting means and a carrier signal. It is predicted that the gate pulse generating means for sequentially generating positive and negative gate pulses according to the comparison result of the amplitude and the gate pulse generated from the gate pulse generating means will affect the occurrence of DC bias of the transformer. A timing signal generating means for generating a timing signal in response to each of the positive gate pulse and the negative gate pulse; Integrating means for integrating only for a fixed period from birth, deviation calculating means for calculating a deviation of each integrated value of the integrating means for each generation cycle of the gate pulse, and a calculated value of the deviation calculating means for the modulated wave signal adjusting means And a switching element control means for sequentially applying a gate pulse from the gate pulse generation means to each switching element to control the driving of each switching element. Control device. 18. A power supply system comprising: a transformer connected to a power supply system; a power converter connected to the power supply system via the transformer; and a capacitor connected to a DC input side of the power converter. 18. A self-excited var compensator using the device according to any one of claims 1 to 17 as a device for controlling driving of a group of switching elements constituting the power converter. apparatus. 19. A DC power transmission system comprising a power converter connected to a power supply system via a transformer and a power converter connected to a load via a transformer via a DC transmission line. And a device for controlling the driving of a group of switching elements constituting the power converter.
7. A DC power transmission system using any one of the items 7.