JP2644590B2 - Voltage fluctuation compensator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage fluctuation compensating device for preventing a voltage fluctuation in a distribution system.

[Conventional technology]

FIG. 5 shows, for example, Mitsubishi Electric Technical Report Vo1.62, No. 6, 1988, p.
FIG. 10 is a circuit diagram showing a conventional voltage fluctuation compensator disclosed in 20 papers “Active filters and their applications”. In the figure, (1) is a power supply, (2) and (3) are resistors R and reactance X existing in the power supply system, and (4) is a load-side bus, whose voltage V is a load voltage to be compensated. . (5) the load whose power fluctuates, and (6)
Is a reactive power compensator connected in parallel with the load (5) to the load-side bus (4), and (7) also detects detection outputs from the current transformer (8) and the transformer (9) as load detecting means. a controller for controlling the output reactive power -JQ _c of the reactive power compensator (6) and.

The reactive power compensator (6) is composed of, for example, an active filter using an automatic inverter as shown in FIG. FIG. 6 is a diagram showing the circuit configuration of the active filter, where (10a) to (10c) are reactors, and (11a) to
(11f) is a transistor switch, (12) is a capacitor, and (13a) and (13b) are current transformers for detecting the output power of the active filter. The control device (7)
Is composed of the following circuits. (14) a detection circuit which receives the voltage VA detected by the transformer (9) and the current IA detected by the current transformer (8), and detects active power P and reactive power Q of the load;
(15) is a current control circuit that controls the output current using the output value of the detection circuit (14) as a reference signal and the current IC detected by the current transformer (13) as a feedback signal, and (16) is a current control circuit ( 15) is a PWM circuit for modulating the output signal, and the output is a transistor switch (11a) to (11f)
Is supplied to the active filter (6) as an ON-OFF signal.

Next, the operation will be described. DC voltage Ed which is charged in the capacitor (12) in Figure 6 is PWM-modulated by the transistor switch (11a) ~ (11f), is converted to V _I becomes the alternating voltage.

The voltage V _I is supplied to the reactor (10) via the load side bus (4). Therefore, the operation of the active filter (6) can be represented by the equivalent circuit of FIG.
When the output voltage V _I of the active filter as shown in FIG. 8 (a) larger than the load bus voltage V phase lead flowing a reactive power to the active filter, The output of the active filter as shown in FIG. (B) the voltage V _I load bus voltage V
If it is smaller, it operates so that the late-phase reactive power flows through the active filter.

Next, a voltage fluctuation compensation method by the reactive power compensator (6) will be described. Fig. 9 shows the load voltage V and the reactive reactive power
Is a time chart showing the time course of Q _C and the power supply-side reactive power Q _O. Now, set the resistance of the power system to R (%) (10MVA
Base), reactance X (%) (those 10MVA base), and was unloaded to a time T = T ₁ is time T = T ₁
Suppose that a load of active power P (KW) and reactive power Q (KVAR) is applied. With this load application, the load voltage V drops by ΔV shown in the following equation. (FIG. 9 (a)) ΔV = (RP + XQ) × 10 ^{-4 The} control device (7) detects the P and Q detection circuits (14) of this load and immediately controls the current control circuit (15) and adjust the PWM control circuit (16), flow to the leading phase reactive power Q _C (KVAR) reactive power compensator to the time T _2, after the which is obtained by the following equation so as to zero the voltage drop [Delta] V (6). (Figure 9 (b)) ΔV = {R · P + X · (Q-Q C)} × 10 -4 = 0 Therefore, As a result, the reactive power Q _O flowing to the power supply side Next power supply power factor continues becomes time advance T = T ₂ later. (FIG. 9 (c)) This progress increases as the value of R / X increases, and the power factor on the power supply side deteriorates.

[Problems to be solved by the invention]

Since the conventional voltage compensator is configured as described above, if the load voltage is to be kept constant, it is necessary to compensate also for the voltage drop due to the resistance R on the power supply side. Therefore, there is a problem that the power factor on the power supply side deteriorates and the power loss due to the power supply impedance increases.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a voltage compensating device capable of preventing a power factor on a power supply from deteriorating and compensating for a change in load voltage. .

[Means for solving the problem]

The voltage compensator according to the present invention includes, in addition to the reactive power compensator, a voltage adjuster that detects the magnitude of the line voltage on the distribution line side of the power supply and automatically compensates for the fluctuation of the load voltage, Among the voltage fluctuations due to the load power fluctuation, those due to the effective component are compensated by the voltage regulator, and those due to the reactive component are compensated by the reactive power compensator.

[Action]

According to the voltage compensator of the present invention, the voltage fluctuation due to the transient change of the load is compensated over the entire area by the reactive power compensator having a quick response, and when the steady state is reached, the compensation area of the reactive power compensator is gradually increased. In order to induce the operation of the voltage regulator by generating a small amount of power supply voltage fluctuation within a range where there is no problem, the voltage fluctuation due to the effective component is normally the voltage regulator, and the voltage fluctuation due to the invalid component is steadily reduced. This can be compensated by a reactive power compensator.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, (17) is a tap changer, (18) is a voltage transformer, (19) is a tap control circuit, and (20) is (17) to (1).
This is a voltage regulator consisting of 9). Also, (21) is a load-side reactive power detection circuit that detects the reactive power of the load (5), (22) is a load-side active power detection circuit that detects the active power of the load (5), and (23) is a power supply side. (24) is a power supply side reactive power detection circuit that detects reactive power on the power supply side, (25) is an integration circuit, (26) is a compensation capacity calculation circuit, and (27) is a compensation capacity. the output value of the arithmetic circuit (26) as a reference signal, a current control circuit for controlling the output current of the current I _C which is detected by the current transformer (13) as a feedback signal. Reference numeral (28) denotes a PWM circuit for modulating an output signal of the current control circuit (27), the output of which is provided to the active filter (6) as ON-OFF signals of the transistor switches (11a) to (11f). Can be

Next, the operation will be described. FIG. 2 is a timing chart similar to FIG. 9 for explaining the difference in operation from the conventional apparatus. Active power P at time T = T ₁ in what was unloaded to a time T = T ₁ in FIG. 2 (KW),
Detecting the reactive power Q by the reactive power Q load reactive power to the load is being the time T _2, after introduction of (KVAR) (21), for detecting the active power P by the load-side active power detection circuit (22).

On the other hand, reactive power compensator (6) power supply side reactive power Q _O a current transformer for detecting the power supply side of the current from the contact power supply side reactive power detection circuit detects the current through (23) as an input (24) of Ask for. Output of the power supply side reactive power detection circuit (24)
Q _O is input to the integration circuit (25) of the next stage, and after being integrated by the time constant T _I , the integrated output Q _I is input to the compensation capacity calculation circuit (26).

 The compensation capacity calculation circuit (26) performs the following calculation.

The output Q _M of the compensation capacity calculation circuit is input as a current reference signal to the next stage of the current control circuit (26), reactive power compensator by PWM circuit and a current control circuit (26) (27) (6)
Is the same as that of the conventional reactive power compensation apparatus shown in FIG. 5 to control such flow of reactive power -JQ _c equal to Q _M in.

Integrating circuit in relation to the time constant immediately after the time T ₂ (2
5) still because the output Q _I becomes almost zero, the output of the compensation capacity calculation circuit immediately after T ₂ (25) is And therefore the output of the reactive power compensator
Q _{C is} also as shown in Fig. 2 (b). Will be output. As a result, P and Q of the load (5)
The operation that suppresses the voltage drop due to the above to zero is the same as the conventional reactive power compensator.

In this case, as shown in FIG. 2 (c), the reactive power Q _O on the power supply side is However, since this reactive power Q _O is detected by the power supply side reactive power detection circuit (23) and integrated by the integration circuit (23) with a time constant T _I , the output Q _I of the integration circuit (23) is compensated. In the capacity calculation circuit (25), the subtraction is performed and the calculation as in the following equation is performed.

Time constant output Q _I of thus time T _2, after the integration circuit (23)
Q _M is reduced gradually as the coming increase in T _I, the output Q _C of the reactive power compensator (6) gradually becomes to come reduced. As a result, as shown in FIG.
Although come down gradually with a decrease in Q _C, reduction of the load voltage V is input to tap control circuit is detected (19) by the voltage regulator the voltage transformer (20) (18). Outputs a tap-up signal to the tap control circuit (19) is tapped switcher (17) when it reaches the lower limit value V _L of the switching taps, operates to increase one step the tap at time T _3. As a result, the load voltage V increases by tapping increment [Delta] V _s at time T ₃ as illustrated in Figure 2. Time T ₃ after further var compensator output Q _C is the voltage raising reduced come again load voltage V the time T ₄ again another stage tap reaches the lower limit value V _L of the switching taps in the (6) further work to lift only [Delta] V _S. Thus, the output of the reactive power compensator
By gradually decreasing Q _C and increasing the tap of the voltage regulator (20) to reduce the voltage drop, the load voltage operates so as to fall within a certain range. Gradually decreases the output Q _C of the reactive power compensator (6) When the reactive power of the power supply side
Q _O gradually decreases, and when Q _O becomes 0 normally, the integration circuit (25) stops the integration operation. Therefore, the output Q _C of the reactive power compensator (6) further decreases. Instead, the power becomes calm when the reactive power Q _O on the power supply side is set to zero. Therefore, the output of the reactive power compensator (6) is normally Q _C = Q _L
And the reactive power Q _O = 0 on the power supply side. As a result, the voltage drop X · Q by reactance X of the voltage drop due to the power source impedance is compensated by the reactive power compensator Q _C, a voltage drop across R · P due to the resistance component R in can be compensated by the voltage regulator (20) Become.

The time constant for reducing the output Q _C of the reactive power compensator in the first embodiment described above (6) is determined by the constant T _I of the integrating circuit (25), if the switching taps of the voltage regulator (20) time delay required is not keep up with the time constant of decrease in the output Q _C response time var compensator (6) for switching the tap when such long compared to the time constant T _I, as a result, There is a possibility that the load voltage V may be reduced more than necessary. The second embodiment of the present invention solves this problem. FIG. 3 is a circuit diagram showing the second embodiment.

In FIG. 3, in addition to the first embodiment of FIG. 1, a voltage fluctuation detection circuit (29), a conversion circuit (30), a limiter circuit (31),
A subtraction circuit (32) and an integration circuit (33) are added.

Hereinafter, this operation will be described. When the load is turned at time T ₁ of the FIG. 4, first, the load reactive power detection circuit (21) and the load active power detection circuit (22) operates, the output Q _C of the reactive power compensator is the time T _2, Immediately after And operates to suppress the voltage drop due to P and Q of the load (5) to zero. After that, the reactive power Q _O on the power supply side is detected by the reactive power detection circuit (24) on the power supply side and integrated by the integration circuit (25) with the time constant T _I.

Output Q _I of the integrator circuit (25) in the compensation capacity calculation circuit (26) Output Q _C of the integrating circuit at time T _2, after by performing the calculation of gradual Q _M decreases, the reactive power compensation device as the output Q _I come increased by the time constant T _I (25) (6) Is FIG. 4 (b)
It gradually decreases like. As a result, FIG.
Load the voltage V is coming down gradually with a decrease in Q _C, decrement the voltage variation detecting circuit of the load voltage V as shown in (2
Detected in 9), the detected value V _D is the next stage of the conversion circuit (31)
Are input to the reactive power was equivalent to V _D amount Q _D Is converted to On the other hand, the output Q _O of the power-supply-side reactive power detection circuit (24) is input to the limiter circuit (31), and the output Q _N is Q _N = + Q _LIMIT + Q _LIMIT > Q _O > Q when Q _O ≧ Q _LIMIT when _lIMIT is given a _{Q N = Q O -Q lIMIT>} Q upper limit of Q _O such that Q _N = -Q _lIMIT when the _O and limiting the lower limit value.

Here, the limit value Q _LIMIT of Q _O is determined as follows.

ΔV _LIMIT = X · Q _LIMIT However, [Delta] V _LIMIT is allowable variation width of the load voltage V, X is the reactance component of the distribution line, the output Q _N conversion circuit in the next stage of the subtracting circuit (32) of the limiter circuit (31) ( attenuated output Q _D of 30), the output of the subtracting circuit (30) (Q _N -Q _D) is integrated in the constant T _V time in the integration circuit (33). Integrator (33)
The output Q _V of the input to the compensation capacity calculation circuit (26) Is performed. Var compensator (6) first to output the reactive power Q _C which corresponds to Q _M of the above formula described above in
This is the same as the embodiment.

Thus to detect a voltage variation V _D of the load voltage V, corresponding to the allowable value [Delta] V _LIMIT of the voltage fluctuation. Accompanied with no load voltage V is lowered to gradually reduce the output Q _C of the reactive power compensator (6) for the Q _LIMIT are integral operation using minus the reactive power Q _D corresponding to V _D Is going to be lower than V _LIMIT, the input ((Q _N −Q _D ) of the integrator (33) becomes negative,
Output Q _V of the integrating circuit (33) decrease in the voltage exceeding the allowable voltage fluctuation to operate so as not to reduce the more compensation capacitor Q _C is prevented. On the other hand, the tap switching lower limit of the voltage regulator (20) is set within the range not exceeding V _LIMIT , so the tap rises and the load voltage V is compensated when the response of the tap control circuit catches up. This is the same as the first embodiment.

In the above embodiment, the case where an active filter is used as the reactive power compensating device has been described. However, a reactive power compensating device in which a thyristor switch controls a capacitor or a reactor may be used. Further, the voltage regulator is not limited to the tap switching method, but may be a unit for controlling another voltage, and has the same effect as the above embodiment.

〔The invention's effect〕

As described above, according to the present invention, of the voltage fluctuations caused by the load fluctuations, those caused by the reactance of the distribution line are compensated by the reactive power compensator, and those caused by the resistance of the distribution line are compensated by the voltage regulator. Therefore, the power factor on the power supply side can be improved, and the loss consumed by the resistance of the distribution line can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a voltage fluctuation compensator according to a first embodiment of the present invention, and FIGS. 2 (a), 2 (b) and 2 (c) show the first embodiment.
FIG. 3 is a circuit diagram showing a voltage fluctuation compensating apparatus according to a second embodiment of the present invention, and FIGS. 4 (a), (b) and (c) show the operation of the second embodiment. FIG. 5 is a circuit diagram showing a conventional voltage fluctuation compensator, FIG. 6 is a block diagram of a reactive power compensator, FIG. 7 is an equivalent circuit of an active filter, FIG.
9A and 9B are waveform diagrams showing the output relationship of the active filter, and FIGS. 9A, 9B and 9C are operation time charts showing the operation of the conventional voltage fluctuation compensator. (1) is power supply, (2) is resistance, (3) is reactance,
(4) load side bus, (5) load, (6) reactive power compensator, (7) controller, (8) current transformer, (9)
Is a transformer, (10) is a reactor, (11) is a transistor switch, (12) is a capacitor, (13) is a current transformer, (1)
4) is a detection circuit, (15) is a current control circuit, (16) is a PWM circuit, (17) is a tap changer, (18) is a voltage transformer, (1)
9) is a tap control circuit, (20) is a voltage regulator composed of (17) to (19), (21) is a load-side reactive power detection circuit,
(22) is a load-side active power detection circuit, (23) is a current transformer, (24) is a power supply-side reactive power detection circuit, (25) is an integration circuit, (26) is a compensation capacity calculation circuit, and (27) is Current control circuit, (28) PWM circuit, (29) voltage fluctuation detection circuit, (3
0) is a conversion circuit, (31) is a limiter circuit, (32) is a subtraction circuit, and (33) is an integration circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Baba 3-21 Nishinowari-cho, Mizuho-ku, Nagoya-shi, Aichi (72) Inventor Masatoshi Takeda 1-1-1, Wadazaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Electric Corporation Kobe Works (72) Inventor Tsuyoshi Kumagai 1-1-2 Wadazakicho, Hyogo-ku, Kobe City, Hyogo Prefecture Mitsubishi Electric Corporation Kobe Works (56) References JP-A-56-159936 (JP, A) JP-A-61-98126 (JP, A)

Claims (2)

(57) [Claims] 1. A system for supplying power from a power source to a load via a bus, the system comprising: a reactive power compensator connected to the bus for compensating reactive power of the system; and connection of the reactive power compensator to the bus. A voltage regulator connected to a power supply side from a point and compensating for a change in bus voltage; a first control circuit that detects a change in an effective component and an invalid component of the load and controls an output of the reactive power compensator; A second control circuit that detects reactive power on the power supply side of the reactive power compensator and controls an output of the reactive power compensator so that the reactive power is set to a constant value; And a voltage control circuit for controlling the voltage regulator so as to suppress the output of the reactive power compensator when the load changes. The reactive power on the power supply side is controlled to a desired value by the second control circuit, and the voltage regulation of the bus resulting from controlling the reactive power on the power supply side to the desired value is controlled by the voltage regulator by the voltage control circuit. A voltage fluctuation compensating device, wherein the voltage fluctuation is compensated by controlling the voltage fluctuation. 2. A voltage fluctuation compensating apparatus according to claim 1, wherein a bus voltage detecting circuit for detecting a bus voltage, and an operation of said second control circuit when the bus voltage exceeds a predetermined value. The first control circuit controls the output of the reactive power compensator so that the bus voltage does not fluctuate when the load changes, and reduces the reactive power on the power supply side. The second control circuit controls the voltage to a desired value, and the reactive power limiting circuit limits the operation of the second control circuit when the resulting voltage fluctuation of the bus exceeds a certain value. Characteristic voltage fluctuation compensator.