JPH09201072A - Control device for power converter - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To enable active / reactive current output of a self-excited converter to be effectively controlled within a limit. SOLUTION: A self-excited converter composed of a self-extinguishing element is connected to a power system via a transformer, and changes in active power based on fluctuations in active power flow of a transmission line connected to the power system, etc. In addition to calculating the active / reactive current command to suppress, the active / reactive current reference is calculated by adding a limit based on the current capacity to each command, and the active / reactive current of the power converter is calculated based on these reference. In the controller of the power converter that performs ignition pulse control so as to control the reactive current,
A means for changing the ratio of the limiting active current and reactive current added to the active / reactive current command based on the magnitude of the active power flow of the transmission line was provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-turn-off device (hereinafter, simply referred to as a G-turn, such as a gate turn-off thyristor).
(Hereinafter referred to as "TO"), and relates to a power converter connected to a power system via a transformer, and in particular, a power converter control device that controls active / reactive current of the converter to suppress fluctuations in the power system. Regarding

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. FIG. 3 shows a configuration diagram of a control device of a power converter (hereinafter, referred to as a self-exciting converter) including a GTO.
A self-excited converter 3 is connected to a power system 1 via a transformer 2, and a DC power source 4 such as a superconducting coil is connected to the DC side.

The transformer 5 for instruments, the transformer 6 for instruments, and the active power flow PL of the transmission line 8 measured by the active power detection means 7.
From the stabilization control means 9 for calculating the active / reactive current command so as to suppress the power fluctuation, and the voltage for calculating the reactive current command so as to suppress the voltage fluctuation from the voltage of the power system measured by the voltage detecting means 10. Control means 11, current command limiting means 12 for calculating the active current reference and the reactive current reference by limiting the vector composition of the active current command and the reactive current command within the current capacity, and the active / reactive current detection of the self-excited converter. An effective / reactive current control means 14 for controlling the active / reactive current detected by the means 13 so as to match the active / reactive current reference;
Pulse width modulation (PWM) that determines TO firing timing
It is composed of gate control means 15.

In the current command limiting means 12 shown in FIG. 4, the vector combination of the active current command and the reactive current command is used to limit the current capacity L.
When it exceeds, the reactive current reference is reduced and restricted within the margin (L * L-P0 * PO) ^{1/2 of} the active current reference PO to the current limit L. In this way, the active / reactive current is limited for the purpose of operating within the allowable current withstanding capacity of the semiconductor element.

[0005]

In the above conventional method, the reactive current is reduced so as to limit the magnitude of the combined current of the active and reactive currents within the current capacity. In this method, the active current is given priority and only the reactive current is reduced, so that system voltage control cannot be performed. As a result, if the active power passing through the transmission line is large and the effect of controlling the active power passing through the transmission line by changing the system voltage with the reactive current output of the self-exciting converter is also great, the active power fluctuation suppression capability is inferior. was there.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a control device for a power converter in which the active / reactive current output of a self-excited converter is effectively controlled within a limit. .

[0007]

According to a first aspect of the present invention, there is provided a control device for a power converter, in which a magnitude of a combined current of active and reactive currents exceeds a current capacity limit and is reduced. A means for changing the ratio of the active / reactive current to be reduced according to the amount of active power of the transmission line is provided. As a result, the amount of active power of the power transmission line is detected, and the ratio exceeding the current capacity is reduced and limited by the ratio of the active / reactive current changed in accordance with the amount of active power.

According to a second aspect of the present invention, there is provided a power converter control device according to the first aspect, wherein an active current command and a reactive current command obtained by dividing the detected transmission line passing active power by a coefficient multiplied by a set value are used. It is equipped with means for reducing the same ratio. As a result, the active current command and the reactive current command obtained by dividing the detected active power passing through the transmission line by the coefficient multiplied by the set value are reduced at the same ratio.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Claims 1 and 2 of the present invention shown in FIGS.
The configuration of the self-excited converter according to (1) includes active power detection means 7 for detecting the active power passing through the power transmission line 8 to be stabilized,
Voltage control means for calculating a reactive current command so as to suppress voltage fluctuations from the voltage of the power system measured by the voltage detection means 10.
11, a current command control means 12 for limiting the active / reactive current reference based on the detected passing active power so that the current of the self-exciting converter is within the capacity limit, and a transmission line passing active power detection signal The signal PLO of the magnitude of the passing active power generated through the low-pass filter 16 is multiplied by the short-circuit reactance set value X of the power system viewed from the bus to generate the coefficient A, and the synthesis of the active / reactive current command. Means 18 for dividing the active current command by the coefficient A when the magnitude of the current capacity exceeds the current capacity L, and the vector combined signal B obtained by taking the square root of the sum of the square of the active current command PI and the square of the reactive current command QI.
And the ratio C / of the signal C obtained by adding the current limit L
A means for multiplying the active current command PI by B to calculate the active current reference PO and multiplying the ratio C / B by the reactive current command QI to calculate the reactive current reference QO is provided.

Next, the operation will be described. The active / reactive current command is determined by the stabilization control during active power fluctuation. However, when the combined current of active / reactive current exceeds the current capacity limit value L, the active power line is enabled. The power PLO is detected, and the active / reactive current reference is decreased at a ratio C / B based on the detected active power so that the current of the self-excited converter is within the capacity limit.

When the signal of the magnitude of the passing active power generated by the transmission line passing active power detection signal through the low-pass filter 16 is PLO, and the short-circuit reactance of the power system seen from the bus is X, the reduced reactive power output ΔQ The transmission line active power change ΔPLQ, which should have been changed by

[Equation 1] ΔPLQ = ΔQ * X * PLO

This is the active current ΔP which is likewise reduced.
Change in active power passing through the transmission line that could have been changed by
Adjust the reactive current limiting ratio to be the same as LP.

[Formula 2] ΔPLP = ΔP = ΔPLQ = ΔQ * X * PLO ΔQ = ΔP / (X * PLO)

That is, the active current command is divided by the coefficient A = PLO * X, and this and the reactive current command are limited within the current capacity. (PI * PI + QI * QI) ^1/2 is L or more,

## EQU3 ## B = (PI / A * PI / A + QI * QI) ^1/2 C = L PO = PI / A * C / B QO = QI * C / B

In this way, the reduced effect becomes equal, and it is possible to prevent only the reactive current from being reduced. As a result, voltage control and power control within the current limit are effectively performed, and fluctuations in the power system can be effectively stabilized.

According to the present embodiment, it is possible to provide a highly reliable device having a function of effectively limiting the active / reactive current output of the self-excited converter. Although the transmission line active power has been described as the signal for suppressing the fluctuation of the power system, the present invention can be similarly applied to the configuration using the voltage frequency instead.

[0016]

As described above, according to the present invention, there is provided a highly reliable power converter control device having a function of effectively limiting the active / reactive current output of a self-exciting converter. Can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a control device for a power converter showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a current command limiting device showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a control device for a power converter showing a conventional example.

FIG. 4 is a configuration diagram of a current command limiting device showing a conventional example.

[Explanation of symbols]

 1 Power System 2 Transformer 3 Power Converter 4 DC Power Supply 5 Meter Transformer 6 Meter Current Transformer 7 Active Power Detection Means 8 Transmission Line 9 Stabilization Control Means 10 Voltage Detection Means 11 Voltage Control Means 12 Current Command Limiting Means 13 active / reactive current detection means 14 active / reactive current control means 15 PWM gate control means 16 low-pass filter 17 multiplication means 18 level determination means 19 division means 20 addition means

Claims (2)

[Claims] 1. A self-excited converter composed of a self-extinguishing element is connected to a power system via a transformer, and active power flow fluctuations of a transmission line connected to the power system or frequency fluctuations of the power system. Alternatively, the active / reactive current command is calculated so as to suppress the active power fluctuation based on the voltage fluctuation of the power system, and the active / reactive current reference is calculated by adding the restriction based on the current capacity to each command. In the controller of the power converter that performs ignition pulse control so as to control the active / reactive current of the power converter based on these criteria, the effective power flow of the transmission line is based on the magnitude of the active power flow. A control device for a power converter, which is provided with a means for changing a ratio of a limiting active current and a reactive current applied to a reactive current command. 2. The means for changing the ratio of the active current and the reactive current of the limit applied to the active / reactive current command, when the active / reactive current command exceeds the current capacity limit, detects the transmission line passing active power. 2. The control device for the power converter according to claim 1, wherein the active current command and the reactive current command divided by a coefficient multiplied by the set value are limited so as to be reduced at the same ratio.