JPH05111162A - Controller for reactive power compensator - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a reactive power compensator that maintains stable control even when the short-circuit capacity of a power system changes and that always has similar transient response characteristics. [Configuration] A signal obtained by multiplying the output of the current detection circuit that detects the current of the reactive power output to the grid by the coefficient of the coefficient circuit, the output of the voltage detection circuit that detects the voltage of the power grid, and the output of the reference voltage setting circuit. A deviation signal and a reactive power compensating apparatus having a reactive power determination arithmetic circuit for determining reactive power output to the grid from the output of a difference circuit for subtracting the difference signal, an adjuster for changing the coefficient of the coefficient circuit, and the adjuster An estimating circuit for estimating a short-circuit capacity of a power system from a voltage and a current caused by changing a coefficient, and a second adjusting circuit for adjusting a coefficient of the coefficient circuit and a constant of the reactive power determination arithmetic circuit from the short-circuit capacity estimated by the estimating circuit. It is a control device of the reactive power compensator having the adjusting circuit of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for a reactive power compensator for suppressing voltage fluctuations in a power system.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional control device for a reactive power compensator. In a reactive power compensator installed in a power source 1 of a power system via an impedance 2 corresponding to a short-circuit capacity of the power system, a voltage detection circuit 4 for detecting a voltage of the power system and an output of the reactive power compensator. The voltage deviation is calculated by the difference circuit 7 from the output of the reference voltage setting circuit 8 for setting the reference value of the system voltage and the output of the voltage detection circuit 4 having the current detection circuit 5 for detecting the current, and the voltage deviation is calculated by the difference circuit 9. And the coefficient circuit 6 subtracts a value obtained by multiplying the output of the current detection circuit 5 by the coefficient Xs, and has a calculation circuit 10 for calculating the reactive power to be output to the power system from this value.

FIG. 7 is a voltage-current characteristic diagram in a steady state of the conventional reactive power compensator constructed as described above. In the figure, the current I is the output current of the reactive power compensator, Vref is the value set by the reference voltage setting device 8, and the current-voltage characteristic between A and B is the control range used for the reactive power control. And its characteristic expression is given by (1). V = Vref + Xs · I (1) where Xs is a coefficient given by the coefficient circuit 6.

FIG. 8 shows a block diagram of a reactive power compensator showing a transient response characteristic. In the figure, X represents the impedance corresponding to the short-circuit capacity of the power system. Further, a simplified version of this figure is shown in FIG. From Fig. 9, the transient response characteristic of the reactive power compensator is the transfer function. It can be seen that the characteristics are changed by X and the characteristics change by X.

[0005]

In the above-mentioned conventional reactive power compensator, since the coefficient Xs of the control device and the constant of the reactive power determining arithmetic circuit are determined in advance for a certain short-circuit capacity of the power system, the short-circuit capacity of the system is determined. If the value changes, the control system may hunt or become unstable.

The present invention has been made in consideration of the above circumstances, and estimates the change in the short-circuit capacity of the system, and according to the change in the short-circuit capacity, the coefficient Xs of the control device and the constant of the reactive power determination arithmetic circuit are set. The adjustment provides a controller for a reactive power compensator that keeps control stable even when the short-circuit capacity of the power system changes and always has the same transient response characteristics.

[0007]

The present invention provides a voltage detection circuit for detecting the voltage of a power system, a current detection circuit for detecting the current of reactive power output to the system, and a coefficient for the output of the current detection circuit. A coefficient circuit for multiplying, a reference voltage setting circuit for setting a reference value of a system voltage, a difference device for calculating a difference between the output of the voltage detection circuit and the output of the reference voltage setting circuit,
In a reactive power compensator having a differential circuit that subtracts the output of the differential circuit and the output of the coefficient circuit, and a reactive power determination arithmetic circuit that determines the reactive power output to the grid from the output of the differential circuit, the coefficient of the coefficient circuit is A regulator to be changed, an estimation circuit for estimating the short-circuit capacity of the power system from the voltage and current resulting from the change of the coefficient by the regulator, a coefficient of the coefficient circuit and the reactive power from the short-circuit capacity estimated by the estimation circuit. A control device for a reactive power compensating device, comprising a second adjusting circuit for adjusting a constant of a decision calculation circuit.

[0008]

With the above means, the control device for the reactive power compensating device of the present invention keeps the gain and phase of the transfer function showing the transient characteristic constant even when the short-circuit capacity of the power system changes, and makes the control system unstable. It is possible to have similar transient characteristics for any power system short-circuit capacity.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, in which a regulator (A) 11 for adjusting a coefficient Xs and a current or a voltage when Xs is changed by the regulator A are short-circuited. Estimator 12 for estimating the impedance X corresponding to the capacity
And a second adjuster (B) 13 for adjusting the coefficient Xs and the constant of the reactive power determination calculation circuit from the estimated impedance.

FIG. 2 shows the voltage-current characteristics and power system characteristics of the reactive power compensator in the steady state. In FIG. 2, (a) is the voltage-current characteristic of the current reactive power compensator, and is represented by equation (3). V = Vref + Xs1 · I (3) where Xs1 is the value of the current coefficient Xs. (B) is a characteristic of the electric power system and is represented by the equation (4). V = Eo−X · I (4)

At this time, the voltage and current of the power system are (c)
It can be detected by the current detection circuit and the voltage detection circuit. Now, let the current and voltage at this equilibrium point (c) be (I1, V1). (D) is X by the adjuster (1)
It represents the characteristics when s is changed, and is expressed by equation (5). V = Vref + Xs2 · I (5) However, the value of the new coefficient Xs is Xs2. Since the voltage-current characteristic of the reactive power compensator becomes (d), the current-voltage equilibrium point moves to (e). If the current and voltage at this point are (I2, V2), this value can also be detected by the current detector and the voltage detector. The estimator 12 estimates the impedance X corresponding to the short-circuit capacitance from the two equilibrium points (I1, V1) and (I2, V2) by the equation (6).

[0013] The transient response characteristic can be represented by the block diagram of FIG. In order not to change the transient characteristics even if the impedance X corresponding to the short-circuit capacity of the power system changes, the transfer function in FIG. It suffices to keep the gain and phase of the constant. For that purpose, for example, the transfer function G (s) of the reactive power determination arithmetic circuit is set to a gain K.
And transfer function GK (s) other than that can be divided into equation (7)
Is expressed by equation (8).

[0014] Therefore, when the impedance X corresponding to the short-circuit capacity of the power system changes, the regulator (B) uses the formulas (9) and (1
It is sufficient to adjust Xs and K so that (0) holds. X · K = constant (9) Xs · K = constant (10)

FIGS. 3, 4 and 5 compare the transient response of the present invention with that of the conventional transient response. V represents the voltage of the power system, and Q represents the output reactive power of the reactive power compensator. FIG. 3 is a result of designing Xs and G (s) with respect to a short-circuit capacity of a certain electric power system. Therefore, even in the case of the present invention, the transient response is as shown in FIG. FIG. 4 shows a transient response when the short-circuit capacity becomes 1/10 in the conventional one. The reactive power compensator is causing hunting. FIG. 5 shows that the system voltage to be controlled has a transient response similar to that before the short circuit capacity is changed as a result of adjusting Xs and G (s) by estimating that the short circuit capacity becomes 1/10 according to the present invention. Has been realized.

[0016]

As described above, according to the present invention, even if the short-circuit capacity of the system changes, the impedance corresponding to the changed short-circuit capacity is estimated and the coefficients Xs and G (s) of the control system are estimated.
Can be adjusted to provide a reactive power compensator having stable and similar transient response.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit of a reactive power compensator according to the present invention.

FIG. 2 is a voltage-current characteristic diagram of a reactive power compensator according to the present invention.

FIG. 3 is a transient response characteristic diagram of the present invention.

FIG. 4 is a transient response characteristic diagram of the present invention.

FIG. 5 is a transient response characteristic diagram of the present invention.

FIG. 6 is a block diagram of a control circuit of a conventional reactive power compensator.

FIG. 7 is a voltage-current characteristic diagram of a conventional reactive power compensator.

FIG. 8 is a transient characteristic block diagram of the reactive power compensator.

FIG. 9 is a transient characteristic block diagram of the reactive power compensator.

[Explanation of symbols]

 1 ... Power system power supply 2 ... Impedance 3 ... Reactive power compensator 4 ... Voltage detection circuit 5 ... Current detection circuit 6 ... Coefficient circuit 7 ... Difference circuit 8 ... Reference voltage setting circuit 9 ... Addition circuit 10 ... Reactive power determination calculation Circuit 11 ... Regulator (A) 12 ... Estimator 13 ... Regulator (B)

Claims (1)

[Claims] 1. A voltage detection circuit for detecting a voltage of a power system, a current detection circuit for detecting a current of reactive power output to the system, a coefficient circuit for multiplying an output of the current detection circuit by a coefficient, and a system voltage A reference voltage setting circuit for setting a reference value, a differencer for calculating a difference between the output of the voltage detection circuit and the output of the reference voltage setting circuit, and a difference circuit for subtracting the output of the differencer and the output of the coefficient circuit. In a reactive power compensator having a reactive power determination arithmetic circuit that determines reactive power output to the grid from the output of a difference circuit, an adjuster that changes the coefficient of the coefficient circuit and a coefficient that is changed by the adjuster And an estimation circuit for estimating the short-circuit capacity of the electric power system from the voltage and the current, and a second circuit for adjusting the coefficient of the coefficient circuit and the constant of the reactive power determination arithmetic circuit from the short-circuit capacity estimated by the estimation circuit. A controller for a reactive power compensator, comprising a regulating circuit.