JPH04193031A - Monitoring circuit for ac/dc conversion controller - Google Patents

Abstract

PURPOSE:To detect abnormality in DC voltage signal by a constitution wherein a comparing means outputs an 'unmatch' signal based on the difference between a value of a product (DC voltage signal)X(current reference signal) and an effective power signal upon abnormal drop of DC voltage signal whereas another comparing means output a 'match' signal based on matching of two effective power signals. CONSTITUTION:An arithmetic unit 80 operates a product of a DC voltage signal Ed and an current reference signal Idp fed from a minimum value selecting circuit 28C thus obtaining a product P'=EdXIdp. A relation (current reference signal Idp) = (actual DC current Id) is normally satisfied and the product P' is substantially equal to output signals PA, PB from effective power detectors 7A, 7B. When the DC voltage signal Ed becomes abnormal, P'not equal to PA, P'not equal to PB and comparators 81A, 81B output ''unmatch'' signals, When any one of the effective power detectors 7A, 7B is abnormal, a comparator 81C outputs an 'unmatch' signal. An abnormality decision unit 82 outputs an abnormal DC voltage detection signal only when the comparators 81A, 81B output 'unmatch' signals and the comparator 81C output a 'match' signal.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is a method for detecting whether the signal of a DC voltage detector of a DC transmission system or DC interconnection equipment such as a frequency converter is normal. This invention relates to a monitoring circuit for monitoring.

(Prior Art) FIG. 2 shows a schematic block diagram of a conventional AC/DC conversion control device for a DC power transmission system.

The DC sides of the converters IA and IB are each connected via a reactor 2, and the AC sides of each converter IA and 4B are connected to converter transformers 4A and 4B, and a circuit breaker 5A.

It is connected to each AC system 6A, 6B via 5B.

Conventional converters IA and IB include a constant power control circuit 26, a voltage-based current limiting circuit (hereinafter abbreviated as VDCL) 27, constant voltage control circuits 12A and 12B, and constant voltage control circuits 11A and I
IB and constant current control circuits 13A and 13B are provided.

The constant power control circuit 26 supplies a current reference signal to the constant current control circuits ]]A, ]]B so that the power handled by the converters IA and IB follows the power reference signal that is the output of the active power setter 19. decide. At this time, the active power signal input to the constant power control circuit 26 is from one of the active power detectors 7A and 7B.
The selection switch 20 selects the output signal of the detector connected to the converter operating as an inverse converter.

VDCL27 is a circuit that inputs the output signal of the DC voltage detector 15 via the voltage/voltage conversion circuit 16B and limits the current reference signal given to the constant current control circuits 11A and IIB according to the magnitude of the DC voltage. It is. Constant power control circuit 2
In order to limit the signal from 6, the highest tJX value selection with the VDCL27 output signal is performed by the highest /J\ value selection circuit 28C.

For example, when VDCL27 detects a drop in DC voltage when commutation fails in the reverse converter, it limits the current reference signal to a value of /h, and as a result, the DC current is reduced by the constant current control circuit on the forward converter side. Therefore, there are effects such as making it easier for the inverter to recover from a commutation failure.

The constant margin angle control circuits 12A and 12B are the margin angle setter 1.
Converter 1' converts the margin angle reference signal which is the output of 8A and 18B.
It operates so that the margin angles of A and IB follow.

A voltage/voltage conversion circuit 1.6A is provided to detect the voltage reference signal which is the output of the DC voltage setter 14A, 14B and the DC voltage with the DC voltage detector]5, and convert it into a value that is easy to handle in the control circuit. A summing circuit 17A is connected through the summing circuit 17A.

The difference with the DC voltage signal input to 17B is determined by summing circuits 17A and 17B, and the value of the difference is input to constant voltage control circuits IA and 11B, so that the DC voltage follows the voltage reference. It will be controlled to do so. Further, the current reference signal which is the output of the R/IX value selection circuit 28C and the DC current are detected by the DC current detector 21A.

The DC current signal detected at 21.8 and converted by current/voltage conversion circuits 22A and 22B to a value that is easy to handle as a control circuit is input to summing circuits 23A and 23B. By inputting the value of the difference to the constant current control circuits 13A and 13B, the DC current flowing through the DC reactor 2 is controlled to follow the current reference signal.

The switches 24A and 24B are closed only for the converter that operates the converter in reverse, and the current margin setter 25A,
The current margin which is the output of 25B is the summing circuit 2.
It is input to 3A and 23B. This current margin function, the constant margin angle control circuits 12A, 12B, the constant voltage control circuits 11A, IIB, the constant current control circuit 13A,
Due to the function of the control advance angle priority circuits 28A and 28B which output only the output of the converter 13B whose control angle is most advanced, the switch 24B is closed and the switch 24A is closed. is open, the output of the constant voltage control circuit 13A is output to the control advance angle priority circuit 28A, and the output of the low margin angle control circuit 12B and the constant voltage control circuit 13A are output to the control advance angle priority circuit 28B. Among the outputs of the voltage control circuit 11B, the output that is leading as a control angle, generally the output of the constant voltage control circuit 11B, is output. Each of the control advance angle priority circuits 28A
, 28B are input to phase control circuits 29A, 29B, where they are converted into pulse signals that determine the firing timing of the converter, and then sent to a pulse amplification circuit 30A.

The signal is configured to be applied as a gate pulse signal to each converter via 30B.

Configuring the control circuit as described above is a known technique.

(Problems to be Solved by the Invention) In the conventional example shown in FIG. 2, when an abnormality occurs in the detection of DC voltage, the following problems occur.

If the DC voltage signal becomes abnormal in the decreasing direction, VD
The CL27 unnecessarily limits the current reference signal, reducing the DC current and reducing the power handled by the converter.

If such a problem occurs during power interchange between AC systems, there is a risk of negative effects such as a decrease in the frequency of the AC systems.

An object of the present invention is to solve the problems of the conventional example, and to provide a monitoring circuit that detects an abnormality when an abnormality occurs in the detection of DC voltage and prevents it from adversely affecting the grid. It is about providing.

[Structure of the invention]

(Means for Solving the Problems) The means for achieving the objects of the present invention are as follows. Means for comparing a signal equivalent to active power obtained by the product of a DC voltage signal and a current reference signal with an actual detection signal of the active power detector; Means for mutually comparing detection signals of two active power detectors; , and means for determining abnormality of the DC voltage detector from the output of each comparing means.

(Function) If the DC voltage signal drops abnormally, the value of the product (DC voltage signal) x (current reference signal) will differ from the active power signal, so the comparison means will output F-RJ. do. Further, since there is no difference between the two active power signals, the comparing means outputs "match". Based on this output result, the abnormality determination circuit determines that the DC voltage signal is abnormal.

(Example) FIG. 1 is a configuration diagram of an embodiment of the present invention.

In FIG. 1, the same elements as in FIG. 2 are given the same reference numerals. The monitoring circuit of the DC voltage detection circuit includes an arithmetic unit 80, comparators 81A, 81B, and 81C, and an abnormality determiner 82.

The calculator 80 calculates the product of the DC voltage signal (%d) input from the DC voltage detector 15 via the voltage/voltage conversion circuit 16B and the current reference signal Idp output from the minimum value selection circuit 28C, Signal P′ equivalent to active power = EdX d
get p. The response of the constant current circuits 13A and 13B is very fast, and normally (current reference signal Idp) ” (actual DC current L+) is established. Therefore, the output signals of the active power detectors 7A and 7B of the converters LA and IB Usually, it is approximately equal to P^+PR.(P' year P A Tp'=pB) However, the DC voltage detector 15 and the voltage/voltage conversion circuit 16
If the DC voltage signal Ed becomes abnormal due to an abnormality in the DC voltage detection circuit consisting of B, etc., the above relationship does not hold and P'≠
PA, P'≠PB. Comparator 81A.

81B compares P′, PA p / and PB and obtains “
−Complete” outputs “Unmatched”.

Comparator 81C compares PA and P8. if,
If either of the active power detectors 7A, 7B is abnormal, PAf-PR is established and the comparator 81G outputs "mismatch".

The abnormality determiner 82 outputs a DC voltage detection abnormality signal only when the outputs of the comparators 81A and 81B are "mismatch" and the output of the comparator 81C is "match". Active power detector 7A
, 7B is abnormal, either the comparator 81A or 81B outputs "mismatch", but in this case, the output of the comparator 81C is "mismatch", so the abnormality determiner 82 detects the abnormality. No signal is output.

In the above description, when comparing P'+PA+p, a range is appropriately set in the determination value in consideration of the loss of the converter. Furthermore, considering the comparison of the amount of active power in a transient state, in order to match the detection delay of the active power detector, a time limit is appropriately set on the DC voltage signal used for calculating the active power.

As explained above, according to the present invention, when an abnormality occurs in the detection of DC voltage, it is determined whether the detection is abnormal, and if the control system is multiplexed, the faulty series is disconnected and control is performed using the healthy series. Doing so will not adversely affect the system.

Further, when the control system is single, processing such as locking the operation of the VDCL 27 is performed, so that it is possible to prevent an adverse effect on the AC system.

〔Effect of the invention〕

As explained above, according to the present invention, when an abnormality occurs in the detection of DC voltage in DC interconnection equipment, the detection abnormality can be determined, so that it can be determined whether the detection abnormality has an adverse effect on the system or the grid. You can prevent it from happening.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention applied to DC interconnection equipment, and FIG. 2 is a block diagram of a conventional device. LA, IB... converter, 2A, 2B... DC reactor, 4A, 4B... converter transformer, 5A, 5B... breaker, 6A, 6B... AC system. 11A, IIB... constant voltage control circuit. 12A, 12B...constant voltage control circuit, 13A, 13
B... Constant voltage control circuit, 14A, 14B... DC voltage setter, 15A, 15B... DC voltage detector, 16A, 16
B...Voltage/voltage conversion circuit, 1.7A, 17B
, 23A, , 23B...Summing circuit, 18A,
18B... Margin angle setting device, 19... Active power setting device, 20... Selection switch,
21A, 21B, 21C, 21D...DC current detector,
22A, 22B, 22C, 22D...Current/voltage conversion circuit, 24A, 24B...Switch, 25A, 25B...Current margin setter, 26...
Constant power control circuit, 27・Voltage-based current limiting circuit (VDCL), 28A,
28B... Control advance angle priority circuit, 28C... Minimum value selection circuit, 29A, 29B... Phase control circuit, 30A, 30B... Pulse amplification circuit, 7A, 7B...
・Active power detector, 80-・Arithmetic unit, 81A, 81B
, 81C... comparator, 82/abnormality determiner, 8A, 8B
...AC current detector, 9A, 9B...voltage detection transformer, Idp/current reference signal, Ed...DC voltage signal, P
'・Signal equivalent to active power, P A + P R... Output signal of active power detection circuit. Agent Patent Attorney Noriyuki ChikaFigure 1Figure 2

Claims (1)

[Claims] In a control device for an AC/DC converter in which one converter operates as a forward converter and the other converter operates as an inverse converter, two sets of active power detectors are provided for detecting the active power of the converter. , an active power comparison means for comparing the outputs of the two sets of active power detectors and determining whether they match, a DC voltage detector for detecting the DC voltage of the converter, and controlling the active power output of the converter. means for calculating the product of the DC current signal and the output signal of the DC voltage detector for the purpose of determining the output signal, and comparing the output signals of the two sets of active power detectors with the product to determine whether they match or differ. Equipped with two sets of comparison means,
A monitoring circuit for an AC/DC conversion control device, characterized in that when the active power comparison means detects a match and the two sets of comparison means detect a mismatch, it is determined that there is an abnormality in the DC voltage detector.