JPH07122836B2 - Controller for reactive power compensator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for a reactive power compensator, and in particular, by compensating for reactive power fluctuations accompanying load fluctuations, voltage fluctuations in the system The present invention relates to a control device suitable for suppressing the above.

[Prior art]

Reactive power control is performed to ensure voltage stability at the load end of the power system. Reactive power compensation is
Generally, reactive power compensation capacitors and SVC (Static Var Comp
This is done in combination with a reactive power compensator such as an ensator).

Here, a fourth example of the control device of the conventional reactive power compensating device is described.
Shown in the figure. In FIG. 4, the electric power from the AC system 1 is supplied to the load 3 via the reactance 2 of the AC system. In this power system, the reactive power is compensated by a reactive power compensator 4 that gives delayed reactive power and a power capacitor 5 that gives advanced reactive power. The reactive power compensator 4 is controlled by the controller described below.

That is, the current of the load 3 is detected by the AC current transformer 401, the voltage of the AC system connected to the load 3 is detected by the AC voltage transformer 402, and each detected value is input to the reactive power detection circuit 420. The reactive power detection circuit 420 obtains the reactive power value of the load 3 from the AC current detection value and the AC voltage detection value, and outputs the value to the addition circuit 421. The other input terminal of the adder circuit 241 is given a reactive power setpoint Q _P which is set in advance, obtains a difference between the reactive power setpoint Q _P and the reactive power detected value. The obtained deviation value is given to the arithmetic circuit 422 having input characteristics such as integration and first-order delay. The arithmetic circuit 422 obtains a control voltage corresponding to the deviation value and outputs it to the phase controller 408. The phase control device 408 gives a control pulse whose phase is controlled in proportion to the magnitude of the input control voltage to the thyristor switch of the reactive power compensating device 4 to control the firing angle to control the reactive power compensation. .

In summary, the reactive power compensation control device described above increases the reactor current of the reactive power compensator 4 when the reactive power set value Q _P is larger than the reactive power value of the load, and conversely the reactive power set value Q _P is increased. When it is smaller than the reactive power value of the load, the firing phase of the thyristor switch is controlled so as to reduce the reactor current, and the total reactive power of the load power capacitor 5 and the reactive power compensator 4 is set to the set value Q _P. Control so that the value is constant. As a result, the fluctuation of the reactive power of the grid due to the load fluctuation is suppressed and the grid voltage is kept constant.

An example of a conventionally known reactive power compensating device is, for example, "Principle of SVC and application to power system" (Nissin Electric Technical Report Vol.28, No.3 (September 1983)). .

[Problems to be solved by the invention]

However, when the reactive current is detected from the load current and the system voltage as in the above device, it is usually a half cycle or 1 cycle.
Since a cycle time is required, if the load changes abruptly, an overvoltage or a voltage decrease transiently occurs due to the detection delay, which adversely affects surrounding power devices.

As a countermeasure against this, there is also used a system in which the system voltage is detected and the current flowing through the reactor of the reactive power compensator 4 is controlled so that the system voltage becomes a constant value of the set value. . However, since this one detects the AC voltage and makes the control voltage of the phase control circuit 408 from the difference from the set value, the response can be made faster than the above-mentioned one which detects and controls the reactive power, but other than the load. When the state of the AC system (for example, the system impedance, system configuration, etc.) changes, the AC voltage at the point where the load is connected also changes, so when the reactive power compensator operates due to fluctuations other than the load is there.

Accordingly, the present invention provides a control device of a reactive power compensator capable of suppressing the voltage fluctuation of the system by performing the compensation of the reactive power due to the load fluctuation at high speed, excluding the above-mentioned drawbacks of the conventional technology. The purpose is to do.

[Means for solving problems]

In order to solve the above problems, a delay reactive power compensator for detecting load current and load voltage of the power system to compensate for delay reactive power of the power system, and a power capacitor for compensating the lead reactive power are provided. In the reactive power compensator,
A detection circuit for detecting the amount of change in the reactive power, and a control circuit for feeding back a control signal for correcting the detected change amount to zero to the delayed reactive power compensator, wherein the detection circuit is a load. As a detection value of the variation of the reactive power of, the value obtained from the primary combination of the variation of the AC current of the load, the variation of the AC voltage, and the variation of the power factor angle is used. is there.

That is, the present invention focuses on the fact that the reactive power Q of the load in the power system consists of the steady component Q _O and the transient component (change component) ΔQ, and the steady component Q _O is compensated by the power capacitor and the transient component Only ΔQ is to be compensated by the reactive power compensator.

The reactive power Q of the load is represented by the following equation, where e is the alternating voltage of the load, i is the alternating current, and is the power factor angle.

In the above equation, the changes in reactive power, AC voltage, AC current, and power factor angle when the load changes slightly are ΔQ, Δe, and
Putting Δi, Δ, Then, ignoring the small amount of the second or higher order, ΔQ = KeΔe + KiΔi + KΔ (4) is obtained. Here, Ke, Ki, and K are constants, and are obtained by the following equation.

In the above equation, e _O , i _O , and _O represent steady values and can be obtained from the values so far. On the other hand, Δe, Δi, Δ are given by the following equations.

Here, e and i are respectively instantaneous values. Therefore, the change ΔQ in the reactive power can be easily obtained from Δe, Δi, Δ in the equation (7) by the primary coupling equation (4).

Here, the steady-state value Q _O of the reactive power Q is obtained from the equation (6),
If this compensation is performed by a fixed power capacitor or reactor and only the transient term given by equation (4) is compensated by the reactive power compensator, not only the power fluctuation during the system transient due to ΔQ can be suppressed, but Comparing to the case where the var compensator of No. 1 performs the compensation of Q _O + ΔQ, the compensation amount can be as small as ΔQ, and the voltage fluctuation of the system can be suppressed by the var compensator of low cost.

Note that the constants (coefficients) Ke, Ki, K in the equation (4) are (5)
As shown in the equation, it is a function of i _O , e _O , sin _O ,
It is a value determined from a steady value and does not need to be calculated at high speed.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the first embodiment. In FIG. 1, the same parts as those in FIG. 4 (conventional example) are designated by the same reference numerals, and detailed description thereof will be omitted. The difference between FIG. 1 and FIG. 4 is as follows.

First, regarding the reactive power detection circuit, the Δi detection circuit 403
Detects the load current change amount Δi from the detection value of the AC current transformer 401 and outputs a signal having a value obtained by multiplying the change amount Δi by the gain Ki. The Δ detection circuit 404 detects the amount Δ of change in the power factor angle of the load from the detection values of the AC current transformer 401 and the AC voltage transformer 402, and outputs a signal of a value obtained by multiplying this by Δ. The Δe detection circuit 405 detects the amount of change Δe of the AC voltage from the detection value of the AC voltage transformer 402, and outputs a signal having a value obtained by multiplying this by the gain Ke.

The adder 406 includes a Δi detection circuit 403, a Δ detection circuit 404, and a Δ detection circuit 404.
The outputs of the e detection circuit 405 are added to each other to generate a variation amount ΔQ of the reactive power of the load. Reference numeral 407 denotes an operational amplifier circuit which has a characteristic of gain + low-pass filter, and which processes the reactive power variation ΔQ, and 408 a phase control circuit which outputs a gate pulse whose phase is controlled according to the output of the operational amplifier circuit 407. Is.

Next, in FIG. 2, Δi detection circuit 403, Δ detection circuit 404, Δ
The specific circuit of the e detection circuit 405 is shown, but FIG. 2 does not show any specific circuit among the detection circuits, but shows a common form of each circuit. Will be described in different cases.

In FIG. 2, 411 is an absolute value circuit that takes the absolute value (magnitude) of the input signal, 412 is a steady value detection circuit that has a large delay time constant and outputs the steady value of the input signal, and 413 is 411 and 41.
An adder that takes the difference between 2 and 414 is an amplifier that inputs the output of this adder 413 and the steady value obtained by each of the circuits 403, 404, and 405, and multiplies the adder 413 by a coefficient, and P _O is a steady value output terminal. , P ₁ and P ₂ are other steady value input terminals. With such a configuration, in the case of the Δi detection circuit 403, Ki Δi = Ki (| i | − | i _O |) (8) where Ki: gain, ||: absolute value symbol Δ detection circuit 404 Where KΔ = K (|| − | _O |) (9) where K: Gain Δe detection circuit, KeΔe = Ke (| e | − | e _O |) (10) where Then, Ke: gain is obtained. In the case of the Δ detection circuit 404, the absolute value circuit 4
It is assumed that 11 also includes a circuit (not shown) for obtaining the power factor angle from the detected values of the AC voltage e and the load current i.

Therefore, in 406, the variation amount ΔQ of the reactive power due to the load variation is obtained by the following equation.

ΔQ = KiΔi + KΔ + KeΔe (11) The operational amplifier circuit 407 processes the ΔQ, and the phase control circuit 408 outputs a gate pulse according to the result. As a result, the reactor current of the reactive power compensator is controlled so that the variation ΔQ of the reactive power of the load becomes zero.

Here, the stationary values of i _O , _O , and e _O are obtained from past data up to the present time. Also, the coefficients Ki, K, Ke of the equation (11) are
It is a value obtained from the above equation (5) using this steady value,
Each is calculated in the amplifier 414.

In the above embodiment, the change in the power factor angle of the load may be detected by a circuit that detects only the phase change in the load current. This is because, in general, when the voltage phase is large, it can be considered that the voltage is always constant regardless of load fluctuations.

Next, FIG. 3 shows a second embodiment in the case where the load includes a converter such as DC power transmission. In this case, the amount of change in the power factor angle of the load can be detected by the amount of change Δα in the control angle of the converter. Therefore, it can be easily obtained from the output of the control circuit of the converter (= input of the phase control circuit = command value of control angle) by the configuration shown in FIG.

In FIG. 3, the same reference numerals as those in the previous figure indicate the same elements, so only different new elements will be described. 301 is an input transformer of a load, and 302 is an AC to DC (or DC to AC) conversion. Converter, 303 is a DC reactor, 304 is a DC line, 305 is a control circuit of the converter 302, 306
Is a phase control circuit, 431 is a DC current transformer that detects the current of the DC circuit, and 432 is the same as the above-mentioned Δi, Δe detection circuits 403 and 405. From the output voltage of the control circuit of the load converter to the control angle α of the converter. This is a Δα detection circuit for detecting the change amount Δα of
The reason why the control angle change amount Δα can be substituted for the load power factor angle change amount Δ is that the control angle α and the power factor angle can be set equal if the reactance of the input transformer 301 of the load is ignored. Therefore, even with this configuration, the variation amount ΔQ of the reactive power of the load including the converter is ΔQ = KiΔi + KαΔα + KeΔe (12) where Kα: gain can be detected at high speed, and the operational amplifier circuit 407, High-speed reactive power control can be performed by the phase control circuit 408 and the reactive power compensator 4.

〔The invention's effect〕

As described above, according to the present invention, the steady component of the reactive power is compensated by the power capacitor, and only the transient component (change component) is feedback-back compensated based on the detected value. Since the reactive power of the load can be detected and the reactive power can be compensated at high speed, it is possible to suppress overvoltage and voltage drop in the system due to load fluctuation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the control device of the reactive power compensating device of the present invention, and FIG. 2 is Δi, Δ and Δe.
FIG. 3 is a block diagram showing a concrete example of each detection circuit of FIG. 3, FIG. 3 is a block diagram showing a control device of the reactive power compensator of the second embodiment when the present invention is applied to a load including a converter, and FIG.
FIG. 1 is a block diagram showing a control device of a reactive power compensating device showing a conventional example of the present invention. 1 ... AC system, 2 ... AC system reactance, 3 ...
... load, 4 ... reactive power compensator, 5 ... power capacitor, 401 ... AC current transformer, 402 ... AC voltage transformer, 403 ... Δi detection circuit, 404 ... Δ detection circuit, 405
...... Δe detection circuit, 406 ... Adder, 407 ... Operational amplifier circuit, 408 ... Phase control circuit, 411 ... Absolute value circuit, 412 ...
… Steady value detection circuit, 413 …… Adder, 414 …… Amplifier, 43
1 …… DC current transformer, 432 …… Δα detection circuit.

Claims (2)

[Claims] 1. A reactive power compensator comprising a delay reactive power compensator for detecting load current and load voltage of the power system to compensate for delayed reactive power of the power system, and a power capacitor for compensating the lead reactive power. In, a detection circuit that detects the amount of change in the reactive power, and a control circuit that feeds back a control signal that corrects and controls the detected change amount to zero to the delayed reactive power compensator, the detection circuit, As a detection value of the variation of the reactive power of the load, a value obtained from a primary combination of the variation of the AC current of the load, the variation of the AC voltage, and the variation of the power factor angle is used. Control device of reactive power compensator. 2. The detection circuit uses the AC current, AC voltage, and power factor angle of the load as reference values when detecting the amount of change of the AC current of the load, the amount of change of the AC voltage, and the amount of change of the power factor angle. 2. The control device for the reactive power compensator according to claim 1, wherein each of the steady values is used.