JPS619125A - Method of controlling stationary reactive power compensator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for controlling a static var power compensator connected to a power grid and maintaining grid voltage.

[Technical background of the invention and its problems]

In order to suppress voltage fluctuations in power systems, it is necessary to control reactive power, which is the largest cause of voltage fluctuations. For this reason, generally, a static reactive power compensator is supplied with advanced reactive power that is approximately equal to the delayed reactive power of the multi-load.
Voltage fluctuations are suppressed.

FIG. 3 shows a single line diagram and a control block diagram of a conventional static var power compensator. In the figure, 1 is a power system, 2 is a voltage transformer, 3 is a current transformer, 4 is a control device for a static var power compensator, 5 is a compensation reactor, 6 is a compensation capacitor, 7 and 8 are thyristors, and 41 is a Rectifier circuit, 42
43 is a low-pass filter, 43 is a voltage reference circuit, 45 is a summing point, 46 is a transfer function circuit, 47 is a Q-α function generation circuit, 49 is a ignition pulse generation circuit, 49 is a rectifier circuit, 50 is a low-pass filter It is.

Next, the operation will be explained. Static reactive power compensators maintain system voltage by supplying phase leading reactive power or lagging reactive power to the power system.

The voltage transformer 2 detects the υ system voltage, and the rectifier circuit 41 and the low-pass filter 42 convert this voltage into a small syllable DC voltage. Furthermore, the output from the low-pass filter and the output from the voltage reference circuit Okara are input to the addition point material and compared. When the voltage signal from the low-pass filter 42 is lower than the reference voltage from the reference voltage signal, the static reactive power compensator supplies leading phase reactive power, but when it is higher, the static reactive power compensator supplies lagging reactive power. supply,
Maintain grid voltage at reference voltage. The output of the summing point material passes through the summing point 45 and is input to the transfer function circuit 46 .

The transfer function circuit 46 is composed of a proportional-integral circuit, etc., and the circuit configuration is determined so that the static var power compensator is stable and has a high-speed response. The output of the transfer function circuit 46 is Q-α
The signal is input to the function generating circuit 47. Here, thyristor 7
．． The reactive power characteristic Q determined by the phase control (control delay angle α) of 8 is approximated as a function.

The output of the Q-α function generating circuit 47 is input to an ignition pulse generating circuit, which is comprised of a circuit for generating gate pulses to be applied to the thyristors 7 and 8.

Furthermore, the current flowing through the compensation reactor 5 and the compensation capacitor 6 is detected by the current transformer 3 and is inputted to the rectifier circuit 49.

The output of the rectifier circuit 49 is input to a low-pass filter 50, which suppresses ripples in the same manner as the low-pass filter 42. Further, the output of the low-pass filter 5o is input to an addition point 45 to form a feedback loop. In this manner, the static var compensator operates to suppress the deviation of the system voltage from the reference voltage.

Furthermore, the operation of voltage control will be explained using FIG. This figure (a) shows the control characteristics of the static var power compensator.

In FIG. 4(a), between O and A, the compensation reactor 5 is opened by the thyristors 7 and 8, and only the compensation capacitor 6 is connected, and the area where the phase-advanced reactive current changes in proportion to the voltage, A-B. The constant voltage characteristics are maintained by the control of the thyristor 7.8 during the period 1. ,,, B-C Ewi! 1X77
,! :8 yo 2, ah This is the region where the continuous reactive current changes in proportion to the voltage when the current of the Yariakudle 5 is maximized.

The slope between A and B is determined by the deviation signal between the reference voltage signal and the grid voltage and the control gain of the transfer function circuit 46.
Usually, it is selected so that 100% of the capacity of the static var compensator can be controlled with a voltage fluctuation of about 1 to 5 inches. ■. The point is the reference point of the grid voltage. Figure 4 (a) OA-B characteristic equation I:=+(V-v.) ・・・・・・・・・・・・・・・
...When expressed as (1), the slope of this characteristic is given by 1/1. K, is the system voltage ■ and the reference voltage v0 (
This is the amount that determines how many times the output of the static var power compensator should be increased relative to the difference between the set value (set value), that is, the change from the set value, and is called the gain of the control system. Therefore, in the characteristic between A and B of FIG. 4 (al), as the gain is increased by 1, the slope becomes smaller and the characteristic becomes closer to the horizontal, and as the gain is decreased, the slope becomes larger.

Next, a description will be given of the response when a static var compensator having such static characteristics is connected to a grid. If the system is simplified and expressed as shown in Figure 4 (b), the system voltage -
The current characteristics are expressed by equation (2).

V = B, -Z, I ・・・・・・・・・
・・・・・・・・・(2) When this characteristic and the characteristic of the static var compensator are superimposed, it becomes N4 diagram (C), and the system! Understand the response to voltage fluctuations. Figure 4 (C)
, the power supply voltage E. The response of the side-stop type reactive power compensator when the value fluctuates is as follows. Assume that when the power supply voltage is Eo, the terminal voltage of the static var compensator is Vo and the output is zero. From this state, the system voltage increases to +ΔE.

When this changes, the voltage-current characteristics of the system become V = (Eo + Δbo) Z, I, and the intersection with the voltage-current characteristics of the static var compensator moves to the right. Therefore, the static var compensator outputs a delayed current I corresponding to the point of intersection with the voltage-current characteristic of the system, and as a result, the terminal voltage of the static var compensator is lowered to 1. Terminal voltage Hv when there is no static reactive power compensator. V because it is ten△Eo. This means that the voltage is suppressed by 10△E0-V.

When a single-phase load such as a train is connected to the power system, the load is a three-phase unbalanced load, so the static var power compensator needs to control each of the three phases individually. In the case of such a load, points a, b, c or a in Figure 4(d)
As shown by points ', b' and 07, control of one of the three phases may be at the end of the constant voltage region. That is, at point A (referred to as γ limit) in FIG. 4(d), the control of phase a is
The control of the a' phase may reach the end (limit) of the constant voltage control region at a point (referred to as the α limit). In the case of (B), in the conventional system, the a-phase or a' phase has no ability to control constant voltage at all, and has no suppressing effect on small disturbance voltage fluctuations.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a control method for a static var power compensator that can exert a suppressing effect even on small disturbance voltage fluctuations.

[Summary of the invention]

In order to achieve this objective, the present invention monitors the ratio of each phase, changes the control amount of the phase that has reached the end of the constant voltage control region to the arithmetic average value of the control amounts of other phases, and This is characterized by the ability to suppress voltage fluctuations caused by disturbances by drawing into a constant voltage control region.

[Embodiments of the invention]

The implementation of the present invention will be described below.

FIG. 1 is a single line diagram and a control block diagram of a static var power compensator for explaining the control method of the present invention. The same numbers as in FIG. 3 indicate the same things, 411 is the arithmetic mean calculation circuit, 414 is the α seat detection circuit, 41
5 is an r limit detection circuit, 416 is an OR circuit, 417
indicates a changeover switch circuit.

FIG. 1 shows the case of constant voltage control for the line R-8, and the same applies to the other lines. The line voltage VR8 is detected by the voltage transformer 2, and a DC signal voltage is generated by the rectifier circuit 41 and filter 42. ! Pressure reference circuit 4
3.21D calculation point material, 45, and transfer function circuit are similar to those explained in FIG. 3, and can be performed in the same manner between lines of other phases. The partner loop average calculation circuit 411 is (h
A calculation of s+Qsy±9 trigrams is performed and used as a control amount for average value control. In addition, the α limit detection circuit 414 and the γ limit detection circuit 415 determine whether the output value from the transfer function circuit 46 is at the end (limit) of the constant voltage control region, and if it reaches the end, the OR circuit 4]6
via the selector switch 417 from A (individual) to B (
average). Changeover switch 417
is normally input to the individual control side of ordinary people, and when there is an output from the OR circuit 416°, the control is switched to the average value control of B.

Taking the arithmetic mean reduces the control gain to the original gain for the phase that has reached the control limit.

As a result, the voltage-current characteristics of the static var-power compensator have a large slope, and are brought into the constant voltage control region. This will be explained using FIG. Characteristic (a) is an example of the characteristics of the conventional method, and the limit is where it crosses the grid characteristics, so it has no suppressing effect on voltage fluctuations below the limit. The characteristics of υ are those of the embodiment according to the present invention, where the control gain is low and the slope is large.
, it can be seen that the voltage is drawn into the constant voltage region.

〔Effect of the invention〕

As explained above, when an unbalance occurs in the load and the control between each line is about to deviate from the constant voltage control area, the control is switched from individual control to average value control, which increases the control ability against small disturbance voltage fluctuations. remains, so it is possible to improve the control ability.

[Brief explanation of drawings]

Fig. 1 is a control block diagram of a static var compensator showing one embodiment of the present invention, Fig. 2 is a voltage-current characteristic diagram for explaining the present invention in detail, and Fig. 3 is a control block diagram of a static var compensator according to an embodiment of the present invention. FIG. 4 is a control block diagram of the power compensator, and FIG. 4 is a control characteristic diagram of the static var power compensator. 1... Power system 2. Voltage transformer 3... Current transformer 4 - Control device 5 for static var power compensator 6. Compensation reactor 6. Compensation capacitor 7.8 Thyristor 41.49. Rectifier circuit 42 .50...Low pass filter Invitation...Voltage reference circuit material, 45...Additional point
46...Transfer function circuit 47-Q-α function generation circuit 48...Ignition pulse generation circuit 414...α limit detection circuit 415...γ limit detection circuit 416...
・OR circuit 417...changeover switch circuit (7
317) Agent: Kensuke Chika, patent attorney (and 1 other person)
name) shi

Claims (1)

[Claims] In order to stabilize the system voltage, a compensation reactor and a compensation capacitor are installed in parallel between the power system and the load, and in a static var compensator that controls the current flowing through the compensation reactor with a thyristor, The static var power compensator is individually provided to perform reactive power compensation for each line, and the control amount is monitored for each line, and the control amount is within the control area of the static var power compensator. A control method for a static var power compensator, characterized in that when a limit is reached, the control between the lines that has reached the limit is switched to be controlled by the arithmetic average value of the control amount for each line. .