JPH07250429A - Protective system for ac/dc converter - Google Patents

Abstract

PURPOSE:To suppress increase of DC current at the time of restarting a BPP by delivering a firing phase pulse for suppressing the DC current based on an interruption signal from a phase control pattern generating circuit for intermediate failure upon receiving an intermediate failure signal from the counterpart end. CONSTITUTION:The protective system for AC/DC converter employs interlocking protection (BPP restart) in which a converter is not stopped in the case of a light failure (intermediate failure) in an AC system but bypath pair operation is effected and a normal operation is reset upon release of failure. Upon receiving an intermediate failure signal 29A from the counterpart end, a phase control circuit 19A delivers a firing phase pulse 24A for suppressing the DC current based on an interruption signal from a phase control pattern generating circuit 30A for intermediate failure. Consequently, the DC current can be suppressed below the overcurrent withstanding capacity of the converter at the time of restarting the BPP.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection system for AC / DC converters used in DC interconnection equipment such as frequency converters.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional DC interconnection facility. As shown in the figure, in the converter of the DC interconnection facility, the DC sides of the converters 1A and 1B are connected by the DC transmission line 3 via the DC reactors 2A and 2B, respectively, and the AC sides of the converters 1A and 1B are connected. Is the transformer for converter 4
A, 4B and circuit breakers 5A, 5B are connected to AC systems 6A, 6B, respectively.
The DC voltage signals detected by the DC voltage detectors 7A and 7B are converted by the voltage conversion circuits 8A and 8B into voltage levels that can be taken into the converter control device. The DC current signals detected by the DC current detectors 9A and 9B are the current-voltage conversion circuits 10A and 10B.
Are converted into voltage levels that can be taken into the converter control devices 15A and 15B.

Further, the converter control devices 15A and 15B are
It is composed of a protection interlocking circuit of control circuits 12A, 12B and 13A, 13B. The configuration of the converter control device 15A is shown in FIG.
Shown in. The same applies to the configuration of 15B. The DC voltage detection value from the voltage conversion circuit 8A and the DC current detection value from the current / voltage conversion circuit 10A are input to the control circuit 12A. The output of the selection circuit 16A is the output of the constant current control circuit 17A during the operation of the forward converter, and the constant voltage control circuit 18A during the operation of the inverse converter.
Are configured to be selected. The phase control circuit 19A calculates a pulse signal that determines the ignition timing of the converter according to the output of the selection circuit 16A.

By the way, when a serious accident occurs in which the converter has to be stopped in the AC system or the DC system, the protection device 14A (hereinafter referred to as a major failure) detects the accident and detects the converter control device. A serious failure detection signal 26A is output to 15A according to the content of the accident. Upon receiving the serious failure detection signal, the converter control device 15A outputs a serious failure protection interlocking signal 25A to the phase control circuit 19A according to the accident content by the protection interlocking circuit 13A to perform the protection interlocking operation and at the same time, if necessary. And outputs a serious failure protection interlocking request signal 27A for requesting the protection interlocking circuit 13B of the converter control device 15B at the other end to perform interlocking protection according to the content of the accident.

[0005] Further, there is an increasing demand for the DC interconnection equipment for the purpose of power interchange to continue the operation without stopping as much as possible. Therefore, in the case of a minor failure in the AC system (hereinafter referred to as "medium failure"), bypass pair operation is performed without stopping the converter, and protection interlocking is performed to return to the normal operating state when the accident is eliminated. . (Hereinafter, this protection interlocking is called BPP restart.) At this time, no special protection interlocking operation is requested from the accident end to the sound end, and the operation is left unattended. When the voltage waveform of the AC system is distorted and the commutation margin angle of the converter may be insufficient, the converter advances the ignition phase to secure the commutation margin angle. The control circuit of such a converter is a conventionally known technique.

[0006]

When a medium failure occurs, the accident end B
When it is put into the PP restart operation, it is equivalent to a state in which the DC circuit is short-circuited at the tip of the DC reactor as viewed from the converter at the sound end, and the DC current increases at this time. At this time, the DC current becomes larger as the value of the DC reactor becomes smaller and the response of the constant current control becomes slower. However, it is necessary to suppress the increase in the direct current at the time of restarting the BPP to be equal to or less than the overcurrent withstanding capacity of the converter.

In recent years, a converter system for reducing the value of the DC reactor has been studied for the purpose of reducing the cost of the converter system. Hereinafter, an operation example of the converter at the time of restarting the conventional BPP will be described.

(1) Medium failure occurs in the AC system. (2) The protective device at the accident end detects a medium failure. (3) Protective device-> Protective interlocking circuit-> Switch to BPP via control circuit.

(The response time of the circuit is T1.) (4) The alternating current increases. (The response time of the DC current detection circuit is T2.) (5) Start of DC current suppression by constant current control.

(The response time of the constant current control is T3.) (6) Recovery from medium failure (7) Restart from BPP operation.

When a medium failure occurs in the AC system, the delay time until the sound end starts suppressing the increase in DC current is T
It is the sum of 1, T2 and T3. For this reason, depending on the system, the suppression of the increase in the direct current at the time of restarting the BPP becomes insufficient, and there is a possibility that the converter may be damaged by exceeding the overcurrent withstanding capacity of the converter just by turning on the BPP due to a medium failure. In addition, there is a risk that the system will shift from a medium failure to a severe DC overcurrent failure, resulting in an unnecessary system stoppage.

When the converter advances in beta, the DC voltage drops sharply, and the DC current increases at this time. This DC current becomes larger as the value of the DC reactor is smaller and the response of the constant current control is slower. However, it is necessary to suppress the increase in DC current during beta advancement to the level equal to or less than the overcurrent withstanding capability of the converter.

In recent years, a converter system for reducing the value of the DC reactor has been studied for the purpose of reducing the cost of the converter system. Hereinafter, an operation example of the converter at the time of restarting the beta advance of the conventional method will be shown.

(1) Waveform distortion occurs in the AC system. (2) The protective device at the accident end detects the waveform distortion. (3) Go through beta via protection device-> protection interlocking circuit-> control circuit.

(The response time of the circuit is T4.) (4) The direct current increases. (The response time of the DC current detection circuit is T5.) (5) Start of DC current suppression by constant current control (Response time of constant current control is T6.) (6) Waveform distortion state to normal AC waveform Return to.

(7) Return from beta advancement. When a medium failure occurs in the AC system, the delay time until the healthy end starts suppressing the increase in DC current is T4, T5, T6.
Is the sum of For this reason, depending on the system, the suppression of the increase in the DC current during the beta advancement becomes insufficient, and there is a possibility that the system may go into a serious failure due to the DC overcurrent just by putting it in the beta advancement, resulting in an unnecessary system stoppage.

The present invention has been made in view of the above circumstances. Claim 1 of the present invention is directed to a method of protecting an AC / DC converter of a DC interconnection facility for suppressing an increase in DC current at BPP restart. The purpose is to provide. It is another object of the present invention to provide a protection method for an AC / DC converter of a DC interconnection facility for suppressing an increase in DC current during beta advancement.

[0018]

In order to achieve the above object, the first aspect of the present invention provides a protection system for an AC / DC converter of a DC interconnection facility such as a frequency conversion device, in which a minor failure in an AC system ( (Medium failure), this failure detection signal is transmitted to the converter at the sound end, and a controller for controlling the ignition phase of the converter at the sound end in the direction of suppressing the increase in DC current is provided. Characterize.

A second aspect of the present invention provides a protection system for an AC / DC converter of a DC interconnection facility such as a frequency conversion device,
When advancing the firing angle to secure the commutation margin of the converter due to voltage waveform distortion of the AC system, etc., the firing angle advance detection signal for advancing this firing angle is transmitted to the converter at the sound end, The present invention is characterized in that a control device is provided for controlling the ignition phase of the converter at the sound end so as to suppress an increase in DC current.

[0020]

According to the first aspect of the present invention, when a medium failure occurs in the AC system, the delay time until the sound end starts suppressing the increase of the DC current can be made shorter than the response delay time of the conventional method. When the accident end is put into the BPP operation due to the occurrence of a middle failure, the healthy end reduces the direct current almost at the same time, so that the increase in the direct current can be effectively suppressed. Therefore, B
The increase of the direct current at the time of restarting the PP can be suppressed below the overcurrent withstanding capacity of the converter.

According to the second aspect of the present invention, when a middle failure occurs in the AC system, the delay time until the sound end starts suppressing the increase of the DC current can be made shorter than the response delay time of the conventional method. Therefore, if beta advancement is performed, the healthy end reduces the direct current almost at the same time, so that the increase in the direct current can be effectively suppressed. Therefore, the increase of the direct current at the time of beta advance can be suppressed below the overcurrent withstanding capacity of the converter.

[0022]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention (corresponding to claim 1). The configuration of this embodiment different from that of the prior art example of FIG. 3 which has already been described is a phase control pattern generating circuit for medium failure at the time of receiving a medium failure detection signal 29A from the other end and outputting an ignition phase control pattern to the phase control circuit 19A. Since only the configuration in which 30A is provided and other configurations are the same, the same reference numerals are given to the same components and the description thereof will be omitted.

Next, the operation of this embodiment will be described.
In the present embodiment, when the medium fault detection signal 29A from the other end is received, the interrupt signal from the medium fault phase control pattern generation circuit 30A is received, and the phase control circuit 19A outputs the ignition phase for suppressing the DC current. .

Here, a flow of an operation example of the converter when the BPP is restarted in this embodiment will be shown below. (1) Medium failure occurred in the AC system. (2) The protection circuit at the accident end detects a medium failure.

(3) A medium failure detection signal is transmitted to the sound end. (4) Sound end: The ignition phase pattern generation circuit receives the medium failure detection signal and outputs the ignition phase for controlling the DC current to the phase control circuit.

(The response time of the circuit is T7.) Accident end: Accident end protection circuit-> B via the accident end control circuit
Put into PP. (The response time of the circuit is T1.) (5) Medium failure recovery (6) Restart from BPP operation.

When a medium failure occurs in the AC system, the delay time until the sound end starts suppressing the increase of the DC current is the operation delay time T7 of the electronic circuit. This operation delay time T7
Can be made shorter than the conventional response delays T2 and T3 shown in FIG. Therefore, the accident end is BPP
When it is put into operation, the DC current is reduced at the sound end almost at the same time, so that the increase in DC current can be effectively suppressed.

FIG. 2 is a block diagram of another embodiment of the present invention (corresponding to claim 2). This embodiment is different from the embodiment of FIG. 1 in that a beta advancing phase control pattern generation circuit 30A for receiving a beta advancing signal 29A from the other end and outputting an ignition phase control pattern to the phase control circuit 19A is provided. Only the points are the same, and the other configurations are the same. Therefore, the same reference numerals are given to the same components and the description thereof will be omitted.

Next, the flow of an operation example of the converter at the time of beta advancement of this embodiment will be shown below. (1) Waveform distortion occurs in the AC system. (2) The protective device at the accident end detects the waveform distortion.

(3) Send the beta advance signal to the sound end. (4) Sound end: The firing phase pattern generation circuit receives the beta advance signal and outputs the firing phase for suppressing the direct current to the phase control circuit.

(The response time of the circuit is T8.) Fault end: Fault end protection circuit-> Beta advance is performed via the fault end control circuit. (The response time of the circuit is T4.) (5) Beta advance recovery When a medium failure occurs in the AC system, the delay time until the sound end starts suppressing the increase of the DC current is T8. T8 is an operation delay time of the electronic circuit, and can be shortened as compared with the response delays T5 and T6 of the conventional method shown in FIG. For this reason, when the beta advance is performed, the DC current is reduced at the sound end almost at the same time, so that the increase of the DC current can be effectively suppressed.

According to this embodiment, when the beta advance signal is received from the other end, the phase control circuit receives the interrupt signal from the beta advance phase control pattern generation circuit, and the phase control circuit outputs the ignition phase for suppressing the direct current. .

(Other Embodiments) In each of the above embodiments, an example in which the present invention is applied to a control system of a single system is explained, but the present invention is not limited to this, and a double system, a three system. Needless to say, the same can be applied to a heavy-duty control device.

[0034]

As described above, according to the first aspect of the present invention.
According to the above, when a middle fault occurs in the AC system, the delay time until the sound end starts suppressing the increase of the DC current can be shortened compared to the response delay time of the conventional method. When put into operation, the DC current is reduced at the sound end almost at the same time, so that the increase in DC current can be effectively suppressed. Further, according to claim 2 of the present invention, when a middle failure occurs in the AC system, the delay time until the sound end starts suppressing the increase of the DC current can be shortened compared to the response delay of the conventional method, so the beta advance As a result, the sound end reduces the direct current almost at the same time, so that the increase in the direct current can be effectively suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of another embodiment of the present invention.

FIG. 3 is a block configuration diagram of a conventional DC interconnection facility.

FIG. 4 is a block diagram of the converter control circuit of FIG.

[Explanation of symbols]

1A, 1B ... Converter, 2A, 2B ... DC reactor, 3
… DC transmission lines, 4A, 4B… Transformers for converters, 5A,
5 ... B circuit breaker, 6A, 6B ... AC system, 7A, 7B ...
DC voltage detector, 8A, 8B ... Voltage conversion circuit, 9A, 9
B ... DC current detector, 10A, 10B ... Current-voltage conversion circuit, 11A, 11B ... Pulse generator, 12A, 12B ...
Control circuit, 13A, 13B ... Protection interlocking circuit, 14A, 1
4B ... Protection circuit, 15A, 15B ... Converter control device, 1
6A ... Selection circuit, 17A ... Constant power supply control circuit, 18A ... Constant voltage control circuit, 19A ... Phase control circuit, 20A ... Current reference, 21A ... Voltage reference, 22A ... DC current detection value, 23
A ... DC voltage detection value, 24A ... Firing phase pulse, 25
A, 26A ... Serious failure detection signal, 27A ... Serious failure protection interlock request signal, 28A ... Medium failure detection signal, 29A ... Serious failure protection interlocking signal, 31A ... Beta advance detection signal, 32A ... Opposite end beta advance detection signal, 33A … Phase control pattern generation circuit during beta advance.

Claims (2)

[Claims] 1. In a protection system for an AC / DC converter of a DC interconnection facility such as a frequency converter, when a minor failure (intermediate failure) occurs in the AC system, this failure detection signal is transmitted to the converter at the sound end. A protection system for an AC-DC converter, comprising a control device for controlling the ignition phase of the converter at the sound end so as to suppress an increase in DC current. 2. In a protection system for an AC / DC converter of DC interconnection equipment such as a frequency converter, when advancing the ignition angle to secure a commutation margin angle of the converter due to voltage waveform distortion of an AC system, A control device is provided for transmitting a firing angle advance detection signal for advancing the firing angle to the converter at the sound end, and controlling the ignition phase of the converter at the sound end in a direction to suppress an increase in DC current. Protection system for AC / DC converters.