JPS62269213A - Reactive power compensating device - Google Patents

Abstract

PURPOSE:To prevent opening and closing of an opening/closing control capacitor from occurring frequently, by controlling a wider range than a unit bank capacity of the opening/closing control capacitor for constituting the first reactive power compensating circuit, by the second reactive power compensating circuit, which can adjust continuously an output. CONSTITUTION:When the capacity of a reactor 5 and a fixed capacitor 9 is selected, for instance, so as to compensate a variation of reactive power of one set portion of a motor, and the time limit of a delaying circuit 16 is set in advance in cooperation with an interval at which the motor is brought to an on/off control, a variation of one set of motor can be compensated by a reactive power compensating circuit 10-2. In this way, opening/closing devices 8-1-8-n for constituting the first reactive power compensating circuit 10-1 can avoid a frequent operation, and also, an increase and a decrease of the reactive power corresponding to an increase and a decrease of the number of motors which are being operated can be compensated by a capacitor bank.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a device connected to a power system in parallel with a fluctuating load,
The present invention relates to a reactive power compensator that rapidly supplies reactive power that cancels the reactive power consumed by the load.

[Conventional technology]

FIG. 3 is a circuit diagram showing a conventional reactive power compensator disclosed in, for example, Japanese Unexamined Patent Publication No. 53-19550. In the figure, 1 is the power supply of the power system, 2 is the impedance of the power system, and 3 is the fluctuation loads, 4-1 to 4-n are n capacitor banks, 5 is equal to the unit bank capacity of the above capacitors, and 6-1 to 6-n are connected in series to capacitor banks 4-1 to 4-n, respectively. A semiconductor switch means such as a thyristor is connected to the reactor 5, and 7 is a semiconductor switch means connected in series to the reactor 5.

Next, the operation will be explained. In response to fluctuations in the reactive power consumed by the load 3, the capacitor banks 4-1 to 4-n are turned on or off by the semiconductor switch means 6-1 to 6-n, thereby performing rough adjustment and controlling the capacitor banks 4-1 to 4-n. The reactor current is controlled by the semiconductor switch means 7 connected in series to the glue handle 5, which has a size equal to the unit capacity of 4-1 to 4-n. The phase of the current is controlled, thereby making fine adjustments to fluctuations in the reactive power of the load 3 and compensating for the reactive power.

[Problem that the invention seeks to solve]

Conventional reactive power compensators are configured as described above, so the number of capacitor banks that are input for a certain output reactive power is uniquely determined, and the load fluctuates before and after the point at which the capacitor banks switch. In this case, one unit bank is turned on and off even for small fluctuations. As a result, mechanical switchgear cannot be used due to frequent operations.

There is a problem in that it is necessary to use semiconductor switching means that is expensive and has a large loss.

This invention was made in order to solve the above-mentioned problems. By significantly reducing the frequency of opening and closing of the capacitor bank, the capacitor bank is controlled by a mechanical switching device, and an ineffective system that is inexpensive and has low loss can be used. The purpose is to obtain a power compensation device.

[Means for solving problems]

The reactive power compensation device according to the present invention includes a first reactive power compensation circuit comprising a plurality of capacitor banks divided into several banks and a switching means connected in series with the capacitor banks, and a reactor current using a semiconductor switch means. a second reactive power compensation circuit capable of continuously adjusting the output through phase control and having a capacitor having a larger capacity than the unit bank capacity of the capacitor; A control means is provided for controlling the capacitor bank of the power compensation circuit to open or close the capacitor bank after a predetermined time period.

[Effect]

The second reactive power compensation circuit in this invention is as follows.

By continuously controlling a range wider than the unit bank capacity of the capacitor in the first reactive power compensation circuit, opening and closing of the capacitor in the first reactive power compensation circuit is prevented from occurring frequently.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is the power supply of the power system, 2 is the impedance of the power system, 3 is a plurality of variable loads, 4-1 to 4. −
n is a capacitor bank; 5 is a reactor having a capacity larger than the unit bank capacity of the capacitor; 7 is a semiconductor switch means for controlling the phase of the current in the reactor 5; 8-1 to 8-n is the capacitor bank 4-; 1~
A switchgear is connected in series to each of 4-n to turn on and off the grid, 9 is a fixed capacitor, 11 is a CT that detects the current of load 3, and 12 is P that detects the grid voltage.
T, 13 is a reactive power detection circuit that detects the reactive power QL consumed by the load; 14 is an arithmetic circuit that calculates the difference between the reactive power QC and the total of 8 ΣQc of the capacitor banks that are input at the present time; 15 16 is a delay circuit having a predetermined time limit; 17 is a capacitor bank opening/closing control circuit; and 18 is a control circuit for controlling the semiconductor switch means 7.

The above capacitor banks 4-1 to 4-n and the switchgear 8-
1 to 8-n to form the first reactive power compensation circuit 10-1,
The reactor 5, the semiconductor switch means 7, and the fixed capacitor 9 form a second reactive power compensation circuit 10-2, the reactive power detection circuit 13, the calculation circuit 14, and the dead band circuit 1.
5. Control means 20 with delay circuit 16° opening/closing control circuit 17
It consists of

Next, the operation will be explained. Here, capacitor 4-1
Each of the 8 unit banks of ~4-n is Qc, the capacity of the reactor 5 is 3Qc, and the capacity of the fixed capacitor 9 is 1.
The configuration is assumed to be 5Qe.

A second reactive power compensation circuit 10- constituted by a reactor 5, a semiconductor switch means 7, and a fixed capacitor 9.
The output Qsvc of 2 can compensate for any value between ±1.5Qc. (However, 10 represents the leading phase reactive power, and - represents the lagging reactive power.) Now, if the load 3 is, for example, 2 in total,
Consider the case where the reactive power QL of Q, : is being consumed and this is to be compensated for.

As shown by the broken line in FIG. 2(a), the compensating reactive power output outputs a leading phase component of the same capacity in order to compensate for the reactive power 2Qe of the load.

In this case, as shown by the solid line 21 in FIG. 2(b), if two capacitor banks 4 are inserted, the output Qsvc,"Qt,-ΣQe of the arithmetic circuit 14 in FIG. 1 becomes 0. , the reactor 5 outputs a lagging phase component of 1.5Qe, and is controlled so that the sum together with the output of the fixed capacitor 9 becomes 05ve=0 (indicated by operating point A on the solid line).

Consider a case where the reactive power QL of the load increases from this state to QL=2.5Q3.

The output of the arithmetic circuit 13 is Qsve=2, 5 Qe 2
Since Qe=0.5Q, the reactor 5 outputs this lagging phase of IQ, and the sum with the output of the fixed capacitor 9 is Qs
The phase of the semiconductor switch means 7 is controlled so that vc'' 0, 5 Q.

Here, the insensitive fl-circuit 15 has an absolute value I of the input signal Qi.
If Qil is less than 0.5Qc, the output Q. If 1Qil is larger than 0.5Qc, output Q. =±(IQil-0,5Qe) (however, decoding corresponds to the positive/negative of Qi).

Therefore, in this state, the input signal Q i ”Qsvc=0
．． 5Qc, the output Q becomes O, and the delay circuit 16 and capacitor bank opening/closing control circuit 17 do not operate (indicated by operating point B in FIGS. 2(a) to 2(c)).

Here, the reactive power QL of load 3 is further calculated as Q L = 3
If Qc increases, the operating point moves to 0 point in FIGS. 2(a) to 2(c), and the output of the reactive power compensation circuit 10 is controlled so that Qsvc=IQc.

At this time, the output Qo of the dead band circuit 15 = + (I Q
eO,5Qe)=0.5Qe, the delay circuit 5 outputs an output after the set time limit, the capacitor bank opening/closing control circuit 17 operates, and one additional capacitor bank is added. As a result, Qsvc=3Qc 3Qe
=O, and the operating point moves to point D in FIGS. 2(a) to (c). If the load 3 is composed of a variable load such as a plurality of electric motors, each of which is controlled to turn on and off, the reactive power QL of the load changes each time each electric motor is turned on and off. The total reactive power varies depending on the number of motors being operated at the time.

In this case, the capacitances of the reactor 5 and fixed capacitor 9 are selected to compensate for fluctuations in reactive power for one motor, and the time limit of the delay circuit 16 is coordinated with the interval at which the motor is controlled to turn on and off. If this is set, fluctuations in one electric motor will be compensated for by the second reactive power compensation circuit 10-2.
8-1 to 8-n can avoid frequent operations, and can compensate for increases and decreases in reactive power according to increases and decreases in the number of motors being operated using the capacitor bank.

Furthermore, due to the dead band circuit 15 and the delay circuit 16, the operating point of the second reactive power compensation circuit 10-1 is normally ±o, sqe
This means that there is sufficient operating range even if there is a sudden change in the reactive power of the load.

In the above embodiment, the second reactive power compensation circuit 1o has a configuration of a combination of a control reactor and a fixed capacitor, but it may also be a combination of a self-excited inverter and a coupling reactor, and the same effect as in the above embodiment can be obtained. play.

〔Effect of the invention〕

As described above, according to the present invention, the second reactive power compensation circuit that can continuously adjust the output
Since the configuration is configured to control a wider range than the unit bank capacity of the switching control capacitors that make up the reactive power compensation circuit, the switching control capacitors do not open and close frequently, and the mechanical switching device The bank can be controlled, and it has the effect of obtaining a product at low cost and with little loss.

[Brief explanation of the drawing]

FIG. 1 shows a reactive power compensator FL according to an embodiment of the present invention.
2(a) to 2(c) are operation explanatory diagrams for explaining an embodiment of the present invention, and FIG. 3 is a circuit diagram showing a conventional reactive power compensator. 3 is a load, 4-1~4n is a capacitor bank, 8-1~
8-n is a switchgear, 10-1 is a first reactive power compensation circuit, 10-2 is a second reactive power compensation circuit, and 20 is a control means. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Patent applicant Mitsubishi Electric Corporation (C)

Claims (2)

[Claims] (1) A first reactive power compensation circuit consisting of a plurality of capacitors divided into several banks and a switchgear connected in series with each capacitor; a second reactive power compensation circuit whose output can be adjusted; and the second reactive power is calculated by subtracting the reactive power compensated by the first reactive power compensation circuit from the reactive power consumed by the load. When compensation is made from the compensation circuit and the amount subtracted exceeds a certain set level that is 1/2 or more of the unit bank capacity of the capacitor and smaller than the capacity of the second reactive power compensation circuit, a capacity corresponding to the excess amount. a control means for controlling the number of capacitor banks of the first reactive power compensation circuit to open or close after a predetermined time period. (2) The reactive power compensation device according to claim (1), wherein the capacity of the second reactive power compensation circuit is larger than the fluctuation in reactive power for one load.