JPH0614455A - Control device for AC / DC converter - Google Patents

Abstract

(57) [Abstract] [Purpose] A failure occurs in the communication system in the controller of the AC / DC converter that transmits and receives signals between a pair of converters that are interconnected via the DC transmission line via the communication system. However, make sure that the control does not become abnormal. [Configuration] A constant voltage control circuit, a constant current control circuit, and a constant margin angle control circuit for controlling the margin angle of the converter to be constant in order to control the converters provided at both ends of the DC power transmission line, Further, in the AC / DC converter for transmitting / receiving the control signal via a communication system, each of the converters has a DC voltage detection value at its own end, a signal corresponding to a DC current flowing in the DC transmission line, and the DC transmission line. A means for adding a voltage signal obtained by multiplying a signal according to the impedance, and using the added signal as a control signal for voltage control of the converter when the communication system is abnormal. Control device for AC / DC converter.

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 an AC / DC converter, in which a DC power transmission line is provided with a forward converter at one end and an inverse converter at the other end, and both converters are connected by a communication line.

[0002]

2. Description of the Related Art FIG. 2 shows a block diagram of a control device for an AC / DC converter provided at both ends of a conventional DC transmission system.

The DC sides of the converters 1A and 1B are connected by a DC transmission line 3 via DC reactors 2A and 2B, respectively, and the AC side of the converters 1A and 1B via converter transformers 4A and 4B and circuit breakers 5A and 5B, respectively. It is connected to AC systems 6A and 6B.

The conventional converters 1A and 1B are provided with constant margin angle control circuits 12A and 12B, constant voltage control circuits 11A and 11B, and constant current control circuits 13A and 13B, and the constant margin angle control circuits 12A and 12B are provided. The margin angle setting device 18A,
The margin angles of the converters 1A and 1B operate so as to follow the margin angle reference value that is the output of 18B.

In such equipment, the DC transmission line 3
In consideration of the voltage drop due to the constant voltage control circuit 11A, 11
Generally, B is controlled to be constant at the transmission end voltage or constant at the reception end voltage. A voltage / voltage conversion circuit 16 for detecting the detected DC voltage by the DC voltage detectors 15A and 15B, respectively, and converting the detected DC voltage into a value that can be easily handled by the control circuit.
The output value is sent to the other end via the communication line 19 via A and 16B, and the voltage of the self end /
Match the output value of the voltage conversion circuit with the output value of the voltage / voltage conversion circuit at the other end sent via the communication line 19,
A value used for control is selected and input to the summing circuits 17A and 17B depending on whether the voltage is controlled to be constant on the power transmission end side or the voltage is controlled on the power reception end side.
In the summing circuits 17A and 17B, the DC voltage setting device 14
The voltage reference value which is the output of A and 14B and the selection circuit 4
The difference between the DC voltage detection value that is the output value of 0A, 40B is obtained, and the difference value is input to the constant voltage control circuits 11A and 11B, so that the DC voltage of the DC power transmission line 3 follows the voltage reference. Will be controlled to do so.

The current reference value output from the transmission control circuits 26A and 26B and the direct current are converted into direct current detectors 21A and 21A.
The DC current detection value detected by 21B and converted into a value that can be easily handled as a control circuit by the current / voltage conversion circuits 22A and 22B is input to the summing circuits 23A and 23B. By inputting the value of the difference to the constant current control circuits 13A and 13B, the direct current flowing through the direct current transmission line 3 is controlled so as to follow the current reference value.

The switches 24A and 24B are closed only in the converter for operating the reverse converter, and the current margin output from the current margin setting devices 25A and 25B is applied to the summing circuits 23A and 23B. Is entered. This current marker
The function of the gin and the constant margin angle control circuits 12A, 12B,
Of the outputs of the constant voltage control circuits 11A and 11B and the constant current control circuits 13A and 13B, the control lead angle priority circuits 28A and 28B that output only the one with the most advanced control angle of the converter as its output. Assuming that the switch 24B is closed and the switch 24A is opened by the function, the output of the constant current control circuit 13A is output to the control advance angle priority circuit 28A, and the control advance angle priority circuit 28A is output. The output of the constant margin angle control circuit 12B or the output of the constant voltage control circuit 11B which is advancing as the control angle, generally the output of the constant voltage control circuit 11B is output to the circuit 28B. Each of the control lead angle priority circuits 28
The outputs of A and 28B are input to the phase control circuits 29A and 29B, where they are converted into pulse signals that determine the firing timing of the converters, and are output to the respective converters 1A and 1B via the pulse amplifier circuits 30A and 30B. Pulse signal. It is a known technique to configure the control circuit as described above.

[0008]

The conventional control device for the AC / DC converter of FIG. 2 has the following problems.

Generally, when an error occurs in a communication system when data is transmitted and received via communication, the output is held at a previous value and protected when the abnormal state continues for a certain arbitrary time or longer. The operation is performed. However, since communication system abnormalities are often recovered due to burst noise depending on the line, the communication abnormality judgment time is generally much longer than the time taken by the converter control. Is. In such a situation, if the command value such as the DC current command value is maintained at both ends by detecting the abnormality of the communication system, the operation can continue without any abnormality, but the detected value used as the feedback of the control is If the value is retained, it may affect driving.

Generally, the constant voltage control of the DC power transmission converter is performed by detecting the DC voltage at the DC output end of each converter and determining whether the voltage at the power receiving end is constant or the voltage at the power transmitting end is constant. Switches the voltage feedback signal.

If an abnormality occurs in the communication system during the constant voltage control of the power transmission end and the previous value is held, the following problems occur. That is, if the held voltage value is higher than the reference value, the function of constant voltage control (AVR) works in the direction of suppressing the voltage, and as a result, the output voltage decreases. If the held voltage value is lower than the reference value, constant voltage control (AV
The function of R) works in the direction of increasing the voltage, and as a result, the output voltage is high. If the DC voltage is operated at a value different from the rated voltage for several seconds, it will adversely affect the equipment and system.

An object of the present invention is to eliminate the above-mentioned drawbacks, and a forward converter provided at one end of a DC power transmission system and an inverse converter provided at the other end of the DC transmission system are referred to at least a DC voltage. It has a constant voltage control circuit that operates so as to follow the value, a low current control circuit that operates so that the direct current follows the reference value, and a constant margin angle control circuit that controls the margin angle of the converter to be constant. In the control device that transmits and receives the control signal of the other end via the communication system, the constant voltage control is the constant voltage at the transmission end, and an abnormality occurs in the communication system.
An object of the present invention is to provide a control device for an AC / DC converter that can continue constant control of the voltage at the power transmission end without adversely affecting the operation of the converter even when the voltage at the power transmission end cannot be detected normally.

[0013]

In order to achieve the above object, the present invention provides a constant voltage operating to follow a DC voltage reference value in order to control converters provided at both ends of a DC transmission line. It is equipped with a control circuit, a constant current control circuit that operates so as to follow the DC current reference value, and a constant margin angle control circuit that constantly controls the margin angle of the converter, and exchanges control signals via a communication system. In the control device of the AC / DC converter, the respective converters detect a DC voltage detection value at their own end, a signal corresponding to the DC current flowing in the DC transmission line, and the DC transmission line impedance. It is characterized in that it is provided with a means for adding a voltage signal multiplied by a corresponding signal, and the added signal is used as a control signal for voltage control of the converter when the communication system is abnormal.

[0014]

With the above configuration, when the communication system is normal, the DC voltage input value of the constant voltage control circuit is selected by selecting either the voltage detected at the self end or the voltage detected at the other end. Control as. Also, when there is an abnormality in the communication system, in consideration of the voltage drop of the DC transmission line, the detected value of the DC current is multiplied by the impedance of the DC transmission line, and the DC voltage detection value of its own end is added, The value is used as the DC voltage input value of the constant voltage control circuit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention. Elements having the same functions as those in FIGS. 1 and 2 are designated by the same reference numerals and their description is omitted.

The control circuit 100 comprises a constant voltage control circuit 11
A, constant margin angle control circuit 12A, constant current control circuit 13A,
Control lead angle control circuit 28A, DC voltage setting device 14A, summing circuits 17A, 23A, 44A, margin angle setting device 18
A, switches 24A, 46A, current margin setting device 25
A, a current reference value output circuit 27, a DC line impedance setter 42A, a multiplier 43A, a selector 40A, and an AND circuit 45A.

The communication line abnormality detector 41A monitors the communication abnormality state of the transmission control circuit 26A, and when an abnormality occurs, holds the output of the transmission control circuit 26A at the previous value and outputs a communication abnormality signal to the AND circuit 45A. . DC voltage detector 15
The DC voltage detected at A is the voltage / voltage conversion circuit 16A.
The signal is input to the selection circuit 40A via the transmission line and is input to the transmission control circuit 26A and transmitted to the other end. Selection circuit 4
At 0A, the DC voltage detection value of the own end and the DC voltage detection value of the other end input via communication are selected and output depending on whether the voltage control is constant control of the transmission end voltage or constant control of the receiving end voltage. Also, the AND circuit 4 sends a control signal for constant voltage at the transmission end.
Output to 5A. The DC current detected by the DC current detector 21A is input to the summing circuit 23A via the current / voltage conversion circuit 22A and also to the multiplier 43A. The multiplier 43 A multiplies the detected value of the DC current by the output value of the DC line impedance setting unit 42 and outputs the value to the summing circuit 44. In the summing circuit 44A, the output of the multiplier 43A and the DC voltage detection value at its own end are added and output. The AND circuit 45A outputs a switching signal due to the communication abnormality signal from the communication abnormality detection device 41A and the power transmission end voltage constant control signal from the selection circuit 40A. When there is no switching signal at the switch 46A, the selection circuit 40
The output of A is input to the summing circuit 17A, and when there is a switching signal, the output of the summing circuit 44A is input to the summing circuit 17A. The summing circuit 17A takes the difference between the input value and the output of the DC voltage setting unit 14A and inputs the value to the constant voltage control circuit 11A. With the configuration described above, the output value of the DC voltage detector at both ends is selected and used as the input of the constant voltage control circuit when the transmission line voltage is constantly controlled and the communication line is normal. Then
In addition, when there is an abnormality in the communication line, the impedance and DC of the transmission end are considered without considering the DC voltage detection value of the other end, considering the DC voltage detection value of the own end and the voltage drop of the transmission line. The value obtained by multiplying the detected current value is added, and that value is used as the input of the constant voltage control circuit. The operations of the constant margin angle control circuit, the constant current control circuit, and the control advance angle priority circuit are the same as those of the conventional example, and thus the description thereof will be omitted.

[0018]

As described above, according to the present invention, the forward converter provided at one end of the DC transmission system and the inverse converter provided at the other end of the DC power transmission system are made to cause the DC voltage to follow the reference value at least. A constant voltage control circuit that operates, a constant current control circuit that operates so as to make a direct current follow a reference value, and a constant margin angle control circuit that constantly controls the margin angle of the converter,
In the control device that transmits and receives the control signal of the other end via the communication system, even when the constant voltage control is the power transmission end voltage constant control and an abnormality occurs in the communication system, and the voltage of the power transmission end cannot be normally detected, It is possible to continue the constant voltage control at the transmission end without adversely affecting the converter operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a controller of an AC / DC converter according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a control device of a conventional AC / DC converter.

[Explanation of symbols]

1A, 2A ... Conversion device 2A, 2B
... DC reactor 3 ... DC transmission line 4A, 4B
… Transformer transformers 5A, 5B… Breakers 6A, 6B
... AC system 11A, 11B ... Constant voltage control circuit 12A, 12B
... Constant margin angle control circuits 13a, 13b ... Constant current control circuits 14A, 14B
... DC voltage setting device 15A, 15B ... DC voltage detector 16A, 16B
... Voltage / voltage conversion circuits 17A, 17B ... Voltage / voltage conversion circuits 18A, 18B
... Margin setting device 19 ... Communication lines 21A, 21B
... DC current detectors 22A, 22B ... Current / voltage conversion circuits 23A, 23B
... summing circuit 24A, 24B ... switch 25A, 25B
... Current margin setting device 26A, 26B ... Transmission control circuit 27
... current reference value output circuit 28A, 28B ... control advance angle priority circuit 29A, 29B
... Phase control circuit 30A, 30B ... Pulse amplification circuit 40A, 40B
... Selection circuit 41A ... Communication abnormality detection device 43A
… Multiplier 44A… Summing circuit 45A
… And circuit 46… Switch 100A
... Control circuit 42A ... Transmission line impedance setting device

Claims (1)

[Claims] 1. A constant voltage control circuit that operates so as to follow a DC voltage reference value, and an operation that causes a DC current reference value to follow so as to control converters provided at both ends of the DC transmission line. In the controller of the AC / DC converter, which comprises a constant current control circuit for controlling, and a constant margin angle control circuit for controlling the margin angle of the converter to be constant, and transmitting and receiving a control signal through a communication system, The converter comprises means for adding a DC voltage detection value at its own end, a voltage signal obtained by multiplying a signal corresponding to the DC current flowing through the DC transmission line by a signal corresponding to the DC transmission line impedance. A control device for an AC / DC converter, wherein the added signal is used as a control signal for voltage control of the converter when the communication system is abnormal.