JPH03210613A - Controller for reactive power compensator - Google Patents

Abstract

PURPOSE:To obtain the optimum responsiveness by calculating the estimated value of a power impedance from a changed variable of the system voltage produced by the ON/OFF of a static capacitor and a current changed variable, and adjusting the control gain based on the estimated power impedance. CONSTITUTION:A power impedance estimating circuit 18 receives the ON/OFF switch signal of a capacitor 7 and calculates a changed variable DELTAV of the system voltage V and a changed variable DELTAI of a current I and then estimates a power impedance Z as Z = DELTAV/DELTAI. A gain adjusting circuit 19 adjusts the gain Kp of a reactive power deciding circuit 15 in adverse proportion to the estimated impedance value Z. Therefore the transient response of a control circuit 9 is delayed when the value Z is reduced. Thus the gain Kp of the circuit 15 is increased. On the contrary, the transient response of the circuit 9 is accelerated and the hunting is produced with increase of the value Z. In this respect, the gain Kp of the circuit 15 is reduced for stabilization of a system. Thus the reactive power is controlled in a fast and stable way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a control device for a reactive power compensator that suppresses voltage fluctuations in an electric power system.

(Prior Art) FIG. 2 is a block diagram showing an example of a conventional reactive power compensator.

In the figure, a main circuit 3 of a reactive power compensator connected to a power system equivalently represented by an AC power supply 1 and a power supply impedance 2 is constructed by connecting an anti-parallel circuit of thyristors 5 and 6 in series to a reactor 4. has been done.

Further, a static capacitor 7 is usually connected to this power system via a switching circuit 8.

On the other hand, the control circuit 9 detects the voltage of the power system using the voltage detection circuit l.
This detected value V and the reference voltage setting circuit 11
A deviation detection circuit 12 detects a deviation from a voltage reference value vref set to . On the other hand, the current from the power system is detected by the current detection circuit 13, and this detected value I is converted into a value of several % to several 10% by the slope reactance circuit 14 and input to the deviation detection circuit 12. Deviation detection circuit 12
are two voltage input signals V, V,. A deviation output obtained according to the difference in r and the current input signal I is provided to a reactive power determining circuit 15 comprising an amplifier circuit, a phase compensation circuit, and the like. The reactive power determining circuit 15 supplies the reactive power signal to be compensated determined according to the voltage deviation to the Cyrisk firing angle control circuit 1B, and the firing pulse of Cyrisk 5.6 of the main circuit 3 is determined according to the reactive power signal. Generate in phase. This ignition pulse is applied via a pulse amplifier 17 to the gate of the thyristor 5.6.

In such a configuration, when the voltage of the power system decreases, the voltage detection circuit 10 detects the system voltage V, and the deviation between this voltage (■) and the reference value vref is detected by the deviation detection circuit 12.

This deviation may be corrected by the output I of the output current detector I3. The output signal of the deviation detection circuit 12 is further amplified by a reactive power determination circuit 15 to become a reactive power signal, and the firing angle control circuit 16 outputs a firing pulse with a phase corresponding to this signal. This firing pulse output is amplified by pulse amplification 817 to fire thyristor 5.6.

As a result, the delayed current flowing through the reactor 4 is reduced, and a drop in system voltage is suppressed.

Conversely, when the grid voltage increases, thyristors 5 and 6
Feedback control is implemented to control the phase of the ignition pulse to increase the current flowing through the reactor 4 and to suppress the rise in system voltage.

(Problem to be Solved by the Invention) In this conventional reactive power compensator, the gain KP of the reactive power determining circuit 15 is optimized in advance according to the value of the power source impedance Z in order to stabilize and speed up the transient response of the control system. It has established. However, the value of the power supply impedance Z is not constant and varies greatly depending on the operation status of the power system.

For example, the value of power source impedance Z changes due to differences between day and night, seasonal differences, and fluctuations due to expansion of power plants. Therefore, when the power supply impedance 2 becomes small, the gain of the control loop decreases and the transient response becomes slow. Conversely, when the power supply impedance Z becomes large, the gain of the control loop increases, making the response unstable and causing hunting.

The present invention solves the above-mentioned problems associated with variations in power supply impedance, and by estimating the power supply impedance and automatically adjusting the gain of the reactive power determining circuit to a value commensurate with the power supply impedance, the present invention always maintains power even when the power supply impedance changes. An object of the present invention is to provide a reactive power compensator that can obtain optimal responsiveness.

Arrangement 1 of the Invention (Means for Solving the Problems) The present invention provides a means for solving the problems of a static capacitor installed in a power system together with a reactive power compensator, and receiving a signal to turn off the static capacitor, and detecting a system voltage generated by turning on or turning off the static capacitor. The control circuit is equipped with a gain adjustment means that calculates an estimated value of the power supply impedance from the change m in the current and the amount of change in the current, and adjusts the control gain based on this estimated value.

(Function) In the present invention, the estimated value of the power source impedance Z-(-ΔV/Δ1) is calculated by dividing the amount of change ΔV in the system voltage caused by the disconnection of the static capacitor by the current change ΔI at this time. can be calculated. By adjusting the gain of the control means in inverse proportion to this estimated value, a reactive power control device with high speed response and high stability can be realized.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

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

In the same figure, when the power source impedance estimating circuit 18 receives a switching signal to turn on or off the capacitor 7, the power source impedance estimation circuit 18
The change ΔV in the current l and the change ΔI in the current l are calculated, and the power source impedance Z is estimated by calculating Z-ΔV/ΔI.

The gain adjustment circuit 19 adjusts the gain of the reactive power determining circuit 15 in inverse proportion to this estimated impedance value 2.

As a result, when the estimated value 2 of the source impedance becomes smaller, the transient response of the control circuit 9 becomes slower, so the gain KP of the reactive power determining circuit 15 is increased, and conversely, when the estimated value Z of the source impedance becomes larger. is the control circuit 9
Since the transient response becomes faster and hunting occurs, the gain of the reactive power determining circuit 15 is lowered to stabilize the system.

In Fig. 1, the capacitor 7 is replaced with a reactive power compensator (TSC) that is turned off by a syris switch, and the power supply impedance is calculated from the change in the system voltage and current when the TSC is turned off. It is also possible to adjust the gain in the same way.

[Effects of the Invention] As described above, according to the present invention, even if the power source impedance changes depending on the operational status of the power system, the gain is automatically adjusted in the control system, so that fast and stable reactive power control can be achieved. This makes it possible to obtain a highly reliable reactive power compensator.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional reactive power compensator. 1... AC power supply, 2... Power source impedance, 3... Main circuit, 4
...Reactor, 5...Thyristor, 6.
... Cyrisk, 7... Static capacitor, 8... Switching circuit, 9... Control circuit, lO... Voltage detection circuit, 11... Reference voltage setting circuit, 12... Deviation detection circuit, 13... Output current detection circuit, 14... Slope reactance circuit, 15... Reactive power determination circuit, 1G... Firing angle control circuit, 17... Pulse amplifier, 18... Source impedance estimation Circuit, 19...gain adjustment circuit.

Claims (1)

[Claims] A reactive power compensator comprising a main circuit in which a reactor and an anti-parallel connected switching element are connected in series to a power system, and a means for controlling the phase of the switching element so as to maintain the voltage of the power system at a voltage reference value. Receive a signal to turn on or cut off a static capacitor installed in parallel to the device, and divide the change in system voltage that is determined to be due to turning on or cutting off a static capacitor by the change in output current to estimate the source impedance. A control device for a reactive power compensator, characterized in that the control device calculates the estimated value and adjusts the gain of the control means based on the estimated value.