JPH0356035A - Voltage fluctuation compensator - Google Patents

Abstract

PURPOSE:To improve a power factor of a power source side by compensating a voltage variation generated by reactance of a power distribution line of a voltage fluctuation generated due to a fluctuation of a load by a reactive power compensator and a voltage variation generated by resistance of the line by a voltage regulator. CONSTITUTION:When a load 5 is connected, a load side reactive power Q is detected in a CT 8 by a detector 21, a load side effective power P is detected in the CT 8 and a PT 9 by a detector 22, and input to a compensating capacity calculator 26. On the other hand, a reactive power Q0 of a power source side is detected from a CT 23 by a detector 24, integrated by a time constant TI to become QI, which is input to the calculator 26. The calculator 26 obtains a current reference signal QM from the data P, Q, Q0, drives a PWM circuit 28 through a current controller 27, its output compensates the reactive power by a compensator 6, and a reactive power -jQC equal to the reference QM is supplied. When the output QI is increased by the constant TI, the signal QM is lowered, the power QC is lowered, a load voltage V is also lowered, but it is compensated by switching the tap of a voltage regulator 20. Thus, the power factor of a power source side is improved, and a loss due to a resistance is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage fluctuation compensator for preventing voltage fluctuations in a power distribution system.

[Conventional technology]

FIG. 5 shows, for example, Mitsubishi Electric Technical Report Vol. 1. 62, interval 6,
1988,? 15-20 is a circuit diagram showing a conventional voltage fluctuation compensator disclosed in the paper "Active filter and its application". In the figure, (1) is the power supply, (2) and (3) are the resistance R and reactance X present in the power supply system, respectively, and (4) is the load side bus, whose voltage V is the load voltage to be compensated. . (5) is a load whose power fluctuates, (6) is a reactive power compensator connected to the load side bus (4) in parallel with load (5), and (7) is a current transformer that is a load detection means. This is a control device that controls the output reactive power -jQc of the reactive power compensator (6) based on the detection outputs from the transformer (8) and the transformer (9).

The reactive power compensator (6) is composed of an active filter using an automatic inverter, as shown in FIG. 6, for example. FIG. 6 is a diagram showing the circuit configuration of the active filter, with beam actors (10a) to (IOC), (11
a) to (llf) are transistor switches, (6) is a capacitor, and (13a) and (13b) are current transformers for detecting the output power of the active filter. Further, the control device 11 (7) is composed of the following circuit. a< is a detection circuit that inputs the voltage detected by the transformer (9) and the current detected by the current transformer (8) to detect the active power P and reactive power Q of the load, and Q5 is the detection circuit A current control circuit uses the output value of a< as a reference signal and uses the current IC detected by the current transformer μs as a feedback signal to control the output current. CIQ is a PWM circuit for modulating the output signal of the current control circuit 4. Yes, the output is from the transistor switch (11a)
(1lf) is applied to the active filter (6) as an ON-OFF signal.

Next, the operation will be explained. In FIG. 6, the DC voltage Ed charged in the capacitor (transistor) is PWM modulated by transistor switches (IXa) to (llf),
v! It is converted into an AC voltage.

This voltage ■ is applied to the load side bus (4) via the reactor ClO.
). Therefore, the operation of the active filter (6) can be expressed by the equivalent circuit shown in FIG.
As shown in a), the output chamber pressure Vx of the active filter is set to the load mother. il91 [If the voltage is greater than V, the leading phase reactive power will flow to the active filter, and as shown in the same figure (b), if the output voltage Vx of the active filter is smaller than the load bus voltage V, the lagging reactive power will flow to the active filter. It works as if it were flowing.

Next, a voltage fluctuation compensation method using the reactive power compensator (6) will be explained. Figure 9 shows load voltage V, compensation reactive power Q
FIG. 2 is a time chart diagram showing the passage of time of O and power supply side reactive power Qo. Now, set the resistance of the power supply system to R (%) (1o
MVA base), reactance as X (%) (1o MVA
It is assumed that a load of active power P (KW) and reactive power Q (KVAR) is applied at time 'r='r, which was unloaded until time T = T1 (base). By applying this load, the load voltage V drops by ΔV expressed by the following equation. (Figure 9(a)) ΔV=CR-P+X-Q)x 10
-'The control device (7) detects this load using the P and Q detection circuit αΦ and immediately adjusts the current control circuit α9 and PWM control circuit QQ, and calculates the above voltage drop △V to zero using the following equation. Phase leading reactive power Qo (KVAR) at time T,
Thereafter, it is passed to the reactive power compensator (6). (in Figure 9)) △V= [R-P+X・(Q-QC)l ×lQ-'=
Q Therefore, R QC=Q1X-P (KVAR) As a result, the reactive power Qo flowing to the power supply side continues to advance in phase. (FIG. 9(C)) This advance increases as the value of R/X increases, and the power factor on the power source side deteriorates.

[Problem to be solved by the invention]

Since the conventional voltage compensator is configured as described above, when trying to keep the load voltage constant, the resistance R on the power supply side
Since it is necessary to also compensate for the voltage drop caused by the power source, it is necessary to overcompensate for the phase-advancing reactive power, which poses a problem of deteriorating the power factor on the power source side and increasing power loss due to power source impedance.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a voltage compensator that can prevent deterioration of the power factor on the power source side and compensate for fluctuations in load voltage. .

[Means to solve the problem]

In addition to the reactive power compensator, the voltage compensator according to the present invention is equipped with a voltage regulator on the distribution line side of the power supply that detects the magnitude of the line voltage and automatically compensates for fluctuations in the load voltage, Among voltage fluctuations due to load power fluctuations, those due to active components are compensated by the voltage regulator, and those due to reactive components are compensated by the reactive power compensator.

[Effect]

The voltage compensator in this invention uses a reactive power compensator to compensate for voltage fluctuations caused by transient changes in the load over the entire range, and when a steady state is reached, the compensation range of the reactive power compensator is gradually increased. In order to induce the operation of the voltage regulator by causing a small voltage fluctuation within a range that does not cause any problems, the voltage fluctuation due to the active component is constantly controlled by the voltage regulator, and the voltage fluctuation due to the reactive component is constantly controlled by the voltage regulator. Voltage fluctuations can be compensated for by a reactive power compensator.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, Q7) is a tap changer, (G) is a voltage transformer, α0 is a tap control circuit, and (1) is a voltage regulator composed of Q7) to α9. In addition, Cυ is a load-side reactive power detection circuit that detects the reactive power of the load (5), @ is a load-side active power detection circuit that detects the active power of the load (5),
(To) is a current transformer that detects the current on the power supply side, (To) is a power supply side reactive power detection circuit that detects reactive power on the power supply side,
(To) is an integration circuit, (E) is a compensation capacitance calculation circuit, (A)
is a current control circuit that uses the output value of the compensation capacitance calculation circuit (to) as a reference signal and controls the output current using the current Ic detected by the current transformer αJ as a feedback signal.

Further, (to) is a PWM circuit for modulating the output signal of the current control circuit, and its output is given to the active filter as ON-OFF signals of the transistor switches (11a) to (11f).

Next, the operation will be explained. In order to explain the difference in operation from the conventional device, explanation will be given with reference to FIG. 2 using a time chart similar to that of FIG. 9. In Fig. 2, time T = T1
The active power P(
KW), reactive power - (KVAR) is turned on, and after time 1゛2, the reactive power q is increased by the reactive power potency υ on the load side.
is detected, and the active power P is detected by the load side active power detection circuit @
Detect.

On the other hand, the power supply side reactive power Q
Find o. The output QO of the example of the power supply side reactive power detection circuit is input to the next stage gradual dividing circuit 4, and after being integrated with a time constant Tt, the integrated output Ql is input to the compensation capacitance calculation circuit (E).

The compensation capacitance calculation circuit (to) calculates the following equation.

The output QM of this compensation capacitance calculation circuit is input as a current reference signal to the current control circuit @ of the next stage, and the current control circuit (4)
This is similar to the conventional reactive power compensator shown in FIG. 5, and the PWM circuit controls the reactive power compensator (6) so that a reactive 1K force jQc equal to QM flows through the reactive power compensator (6).

Immediately after time T2, the output QI of the integrating circuit (to) is still almost O due to the time constant, so the output of compensation capacitance calculation circuit 1 immediately after T2 is R Q M = Q + (x)P, and therefore the output QO of the reactive power compensator will also be as shown in FIG. 2(b). As a result, P and Q of load (5)
It is similar to the conventional reactive power compensator that it operates so as to suppress the voltage drop due to the voltage drop to O.

As shown in Fig. 2 (C), in this case, the reactive power QO on the power supply side becomes .This reactive power Qo is detected by the power supply side reactive power detection circuit @, and is processed by the time constant TI in the integration circuit @. Since it is integrated, the output QI of the integration circuit @ is output by the compensation capacitance calculation circuit (
In (d), subtraction is performed and the following calculation is performed.

Therefore, after time T2, the output QI of the integrating circuit @ is the time constant T.
As x increases, QM gradually decreases, and the output QC of the reactive power compensator (6) gradually decreases. As a result, the load voltage V
also gradually decreases as Qc decreases, but the decrease in load voltage V is detected by the voltage transformer (1) of the voltage regulator and is input to the tap control circuit α.The lower limit value VL of the tap switching When the tap reaches T, the tap control circuit 4 outputs a tap increase signal to the tap changer α, and operates to raise the tap by one step at time T. As a result, the load voltage V increases at the time as shown in FIG. At time T, the load voltage V increases by the tap increase amount ΔVs.After time T3, the output Qo of the reactive power compensator (6) further decreases, and when the load voltage V reaches the lower limit value VL for tap switching at time T4, it increases again. It operates to raise the voltage by ΔVs by raising the tap one step.In this way, the output QO of the reactive power compensator is gradually decreased, and the tap of the voltage regulator (1) is raised to compensate for the resulting voltage drop. As a result, the load voltage is operated to be within a certain range.As the output QO of the reactive power compensator (6) is decreased, the reactive power Qo on the power supply side gradually decreases and becomes steady. Q
When o becomes 0, the integrating circuit (d) stops the integrating operation, so the output QO of the reactive power compensator (6) does not decrease any further, and the reactive power Qo on the Wl source side is set to 0. It will calm down. Therefore, on a steady basis, the output of the reactive power compensator (6) is Qo = Qt. In addition, the reactive power Qo on the power supply side is equal to o. As a result, the voltage drop due to the reactance X out of the voltage drop due to the power source impedance is X. Q is compensated by the reactive power compensation device Qa, and the voltage drop RP due to the resistance R can be compensated by the voltage regulator @4.

In the first embodiment described above, the time constant for reducing the output QO of the reactive power compensator @ (6) is determined by the time constant TX of the integrating circuit @, and if the time delay required for tap switching of the voltage regulator (7) is longer than the above time constant TI, the response time for tap switching cannot catch up with the time constant of the drop in the output QC of the reactive power compensator (6), and as a result, the load voltage ■ There is a possibility that it may be lowered by more than that. A second embodiment of the present invention solves this problem, and a circuit diagram showing the second embodiment is shown in FIG.

In addition to the first embodiment shown in Fig. 1, Fig. 3 shows a voltage fluctuation detection circuit, a conversion circuit (1), a limiter circuit rule, and a subtraction circuit.
and an integration circuit (to) have been added.

This operation will be explained below. When the load is turned on at time T1 in FIG. 4, first the load reactive power detection circuit till
) and the load active power detection circuit operate, and the output Qo of the reactive power compensator becomes immediately after time T2, and operates so as to suppress the voltage drop due to P and Q of the load (5) to zero. Thereafter, the reactive power Qo on the power source side is detected by the power source side reactive power detection circuit and integrated with the time constant Tt in the integrating circuit (to).

What is the output QI of the integrating circuit @ in the compensation capacitance calculation circuit (e)? By performing the calculation, the integral circuit is formed at time T and thereafter.■■■
As the output QI of the var.
It gradually decreases as shown in Figure (b). As a result, the fourth
As shown in Figure (a), the load pressure ■ gradually decreases as the QO decreases, but this decrease in the load voltage V is detected by the voltage fluctuation detection circuit 4, and the detected value VD is used in the next stage. The reactive power QD (
However, it is converted to QD=X-VD). On the other hand, the output Qo of the power supply side reactive power detection circuit (c) is input to the limiter circuit 0υ, and its output QN is QN=+QLIMIT+Q when Qo≧+QLIMIT
LIMIT >QO >QLIMIT (QN = when D
When Qo-QLIMIT>QO, QN:-QLIMI
A limit is given to the upper limit value and lower limit value of Qo so that T.

Here, the Qo limit value QLIMIT is determined as follows.

ΔVtrMtr = X-QLIMIT However, ΔVLI
MIT is the permissible fluctuation width of the load voltage (■), X is the distribution line actance, and the output QN of the limiter circuit No. 6 is subtracted from the output QD of the converter circuit in the next stage subtraction circuit (■), and the output of the subtraction circuit (1) is (QN-QD) is integrated by the time constant Tv in the integrating circuit (to).

The output Qv of the integrating circuit 1 is input to the compensation capacitance calculation circuit (e) and is subjected to the calculation RQM=Q+(X)·P-Ql-Qv. The reactive power compensator (6) outputs reactive power QO corresponding to QM in the above equation, as in the first embodiment described above.

In this way, the voltage fluctuation VD of the load voltage (■) is detected and corresponds to the permissible voltage fluctuation value ΔVLIMIT. QLIMIT
Since the integral calculation is performed after subtracting the reactive power QD corresponding to VD from
When trying to go below LIMIT, the input of the integrating circuit ρ (
QN-QD) becomes negative and the output Qv of the integrating circuit (to) operates so as not to further reduce the compensation capacitance QO, thereby preventing the voltage from dropping beyond the voltage fluctuation tolerance. On the other hand, the tap switching lower limit value of the voltage regulator (7) is V
Since it is set within a range that does not exceed LIMIT, the tap increases and the load voltage V is compensated when the response of the tap control circuit catches up, as in the first embodiment.

In the above embodiment, an active filter is used as the reactive power compensator, but a reactive power compensator using a thyristor switch to control a capacitor or an actuator may also be used. Furthermore, the voltage regulator is not limited to the tap switching type, and may be any other means for controlling voltage, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, among the voltage fluctuations caused by load fluctuations, those caused by the actance of the distribution line are compensated by the reactive power compensator, and the voltage fluctuations caused by the resistance of the distribution line are compensated for by the voltage regulator. Since the structure is configured to compensate for this, it is possible to improve the power factor on the power source side, and there is an effect that the loss consumed by the resistance of the distribution line can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a voltage fluctuation compensator according to a first embodiment of the present invention, and FIGS. 3 is a circuit diagram showing a voltage fluctuation compensator according to a second embodiment of the present invention, FIGS. 4(a), (b), and (C) are operation time charts showing the operation of the second embodiment, and FIG. The figure is a circuit diagram showing a conventional voltage fluctuation compensator, Figure 6 is a waveform diagram showing the output relationship of the filter, and Figure 9 (a), (b), and (C) are operating times showing the operation of a conventional voltage fluctuation compensator. It is a chart. (1) is the power supply, (2) is the resistance, (3) the beam actance,
(4) is the load side bus, (5) is the load, (6) is the reactive power supplementary device, (7) is the control device, (8) is the current transformer, <9)
is a transformer, αO beam actor, aυ is a transistor switch, A is a capacitor, αJ is a current transformer, α◆ is a detection circuit, αi is a current control circuit, Clt9 is a PWM circuit, α is a tap changer, Oen is A voltage transformer, Ql is a tap control circuit, and a voltage regulator consisting of (17) to α0 is C1.
) is the load side reactive power detection circuit, @ is the load side active power detection circuit, 4 is the current transformer, (d) is the power supply side reactive power detection circuit, 4 is the integrating circuit, (7) is the compensation capacity calculation circuit, ( 5)
is a current control circuit, ＠ is a PWM circuit, 翺 is a voltage fluctuation detection circuit, ■ is a conversion circuit, 0υ is a limiter circuit, work is a subtraction circuit, and ■ is an integration circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In a system that supplies power from a power source to a load via a bus, a reactive power compensator that is connected to the bus and compensates for the reactive power of the system, and a connection point between this reactive power compensator and the bus. a voltage regulator connected to a power supply side to compensate for fluctuations in bus voltage; a first control circuit for detecting changes in active and reactive components of the load to control the output of the reactive power compensator; a second control circuit that detects reactive power on the power source side of the power compensator and controls the output of the reactive power compensator so as to maintain the reactive power at a constant value; a voltage control circuit that controls the voltage regulator so as to suppress the voltage regulator, and when the load changes, the first control circuit controls the output of the reactive power compensator so that the bus voltage does not fluctuate; The reactive power on the power source side is controlled to a desired value by the second control circuit, and the voltage fluctuation of the bus bar that occurs as a result of controlling the reactive power on the power source side to the desired value is controlled by the voltage control circuit to control the voltage regulator. A voltage fluctuation compensator characterized in that the voltage fluctuation is controlled and compensated for. (2) The voltage fluctuation compensator of item 1 above includes a bus voltage detection circuit that detects the bus voltage, and a bus voltage detection circuit that acts to limit the operation of the second control circuit when the bus voltage exceeds a certain value. and a reactive power limiting circuit that controls the output of the reactive power compensator by the first control circuit so that the bus voltage does not fluctuate when the load changes, and controls the reactive power on the power supply side to the second control circuit. The second control circuit controls the second control circuit to a desired value, and when the bus voltage fluctuation that occurs exceeds a certain value, the reactive power limiting circuit limits the operation of the second control circuit. voltage fluctuation compensator.