JPH0630033B2 - Reactive power compensator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive power compensator, and more particularly to a reactive power compensator suitable for application to a power system in which the short-circuit capacity fluctuates greatly.

[Background of the Invention]

This kind of reactive power compensator (Static Var Compensator,
Hereinafter, it may be referred to as "SVC". ) 1 is a typical one, as shown in FIG. 2, a capacitor 2 is provided with a thyristor 3 and a reactive power generator 6 in which a series circuit including a thyristor 3, a reactor 4 and a transformer 5 is connected in parallel. It is composed of a control device 7 that can perform phase control based on a signal from a power source. By controlling the thyristor 3 with a control signal from the control device 7 to control the current I _LS flowing through the reactor 4, the power is consumed by the equipment. Reactive current I _qS = I _CS −
It is a device that can control _ILS continuously.

This SVC 1 is very effective in suppressing power fluctuations in the system due to load fluctuations.

By the way, as shown in FIG. 3 (a), a load 9 is connected to a transmission line 8 composed of a resistance component R and a reactor component jX so that power is supplied from a power source 10 having a voltage V _S to the load 9. when installed the SVC1 in lines and formed by a voltage variation V _d of the installation point of SVC1, as shown in FIG. (b), the current I _p flowing through the transmission _line, I _q and the transmission line impedance R
What is defined as + jX will be described in more detail. That is, assuming that the power supply voltage is _{S 1} , the voltage drop at the power transmission line 8 is ΔV, and the voltage at the power receiving end (load 9) is V _t , the relationship between the power supply voltage _S and other things is _S = _t + Δ. It will be given in (1).

Further, when the load current is I _p −jI _q , the voltage drop Δ
Is, delta = the _{(R + jX) (I p} -jI q) (I R R + I q X) + j (XI p -RI q) ...... (2). Therefore, the relationship between the equations (1) and (2) is shown in FIG. 3 (b). It can be understood that the voltage fluctuation is regulated by the currents I _p and I _q given as V _d and the transmission line impedance (R + jX).

By the way, generally, the impedance of the power transmission line has a relation of R << X, and therefore, the voltage fluctuation V _d is almost dominated by the product of the reactance X of the power transmission line and the reactive current I _q. .

Therefore, as shown in FIG. 3 (a), if the reactance of the transmission line, that is, the back short-circuit impedance X is given, the reactive current I _qL of the load 9 is changed to the reactive current I from the SVC 1.
The thyristor 3 of the _SVC 1 is phase-controlled so that it can be compensated by _qS , whereby the voltage fluctuation V _d can be kept constant and the voltage fluctuation can be suppressed.

FIG. 4 shows the control as described above (this is the constant voltage control "AV
FIG. 3 is a system diagram showing a system including a control device capable of “R”).

In FIG. 4, the SVC 1 includes a reactive power generator 6 and
It is composed of a control device 7.

The reactive power generator 6 is different from the configuration shown in FIG. 2 mainly in that switches 11 and 12 are provided.
There is no other essential difference.

The control device 7 controls the voltage at the power receiving end to the transformer for instrument (PT) 1
3 is taken in and is compared with the voltage setting value V _ref by the subtracter 14 to output its deviation εV, which is given to the constant voltage control (AVR) element 15 and the deviation εV is given from the AVR element 15 The control signal E _C is an automatic pulse phase shifter (A
The control ignition pulse is supplied to the thyristor 3 from the APPS 16 by applying the control ignition pulse to the thyristor 3.

The operation of the SVC 1 having such a configuration will be described. The system (received voltage of the load 9) V _L is taken into the control device 7. The control device 7 detects the power reception voltage V _L via the instrument transformer 13, compares it with the voltage setting value V _ref by the subtractor 14, and outputs the deviation εV. The AVR element 15 which takes in the deviation εV receives the deviation εV as an input, and when the deviation εV becomes large, the output current from the SVC 1 becomes large.
On the contrary, when the deviation εV decreases, the SVC1
A control output E _C is output to reduce the output current from the. The control output E _C is converted into an ignition pulse by the APPS 16, and the phase control of the thyristor valve 3 of the reactive power generator 6 is performed.

With the above operation, when the received voltage V _L becomes large, SV
The output current from C1 increases and acts to decrease the power reception voltage V _L , while when the power reception voltage V _L decreases, the current from SVC1 decreases and acts to increase the power reception voltage V _L. It will be. Therefore, this S
The power receiving point voltage V _L can be kept constant by VC1.

From the above, it can be understood that the loop gain of the AVR system depends on the product of the gain K _f of the AVR element 15 and the short-circuit impedance X.

By the way, the short-circuit impedance X of the system may change depending on the operation. Therefore, in order to optimally operate the SVC, it is necessary to adjust the control system gain K _f according to the state of the system.

As a method of this kind, J. Reported by Belanger et al. "Gain Superviser
for Thyristor Controlled Shunt Compensators) -C
IGRE1984 ”. This method, since that summer to adjust the gain K _f while detecting the vibrating state of the control system, always will be operated in a stable limits, depending on the system condition while a short circuit impedance is large ,
There was a problem that compensation could not be completed even with the installed SVC capacity.

[Object of the Invention]

An object of the present invention is to provide a reactive power compensator (SVC) that can always obtain effective control characteristics even in a system in which the back short-circuit capacity changes due to system operation.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the SVC 1 according to the present invention.

Constant SVC1 shown in FIG. 1 is different at those of FIG. 4, the control device 70, to the constant voltage control means 17 to control the amount of the bus voltage V _L, and control the amount of the receiving end reactive power Q _L Two control loops with the reactive power control means 20 are provided,
And the output Q _V from these two control means 17, 20
Select either one of Q _R A as output Q _C
The point is that the control output selection circuit 30 to be supplied to the PPS 16 is provided and configured.

The constant voltage control means 17 includes a PT 13, a subtractor 14,
It is made of AVR15. Constant reactive power control means 20
Is a current transformer (CT) 2 that detects the current flowing through the load.
1, PT13 and the reactive power detection circuit 22 for detecting the reactive power _{Q f} based on the detection signal from CT21, reactive power _{Q f} from the reactive power detection circuit 22 and compared with a set value Q _ref deviation epsilon _Q a subtracter 23 for outputting, and a reactive power control element 24 for outputting a control output Q _R from the deviation epsilon _Q from the subtractor 23.

Next, the operation of this embodiment will be described.

The constant voltage control means 17 inputs the voltage V _L at the power receiving end as a detection value V _f via the transformer 7 for a meter and, on the other hand, a difference from the set value V _{ref of the} voltage which is set in advance by another means. Is calculated by the subtractor 14, and an output of ε _V = V _f −V _ref (3) is output. The AVR element 15 calculates the control amount Q _V so that this ε _V becomes smaller. Although various methods are conceivable for the calculation algorithm, for example, it can be realized by the following first-order lag element.

Here, K _f is a forward gain, and T _f is a control delay time constant.

Therefore, since Q _V is constantly Q _V = K _f · ε _V (5), the received voltage V _L increases, and when ε _V increases, Q _V also increases and SVC1 Operates so that Q becomes large. Therefore, as described above, the delay reactive current I _q flowing through the power transmission line is increased, the voltage drop ΔV is increased, and the power reception voltage V _L is reduced.

On the contrary, when the power reception voltage V _L is lowered, the operation opposite to the above operation is performed to obtain the effect of increasing the power reception voltage V _L.

Next, the operation of the constant reactive power control means 20 will be described.

The power receiving current is detected by CT21, and the power receiving end voltage V _L is
The PT13 detects them, and inputs these detected amounts to the reactive power detector 22 to detect the reactive power amount Q _f at the power receiving point.
On the other hand, the difference ε _Q between the reactive power set value Q _ref given in advance by another means and the Q _f is obtained by the subtractor 23, and this is used as the input of the reactive power control element 24.

Reactive power control element 24, so that the deviation epsilon _Q is reduced it the larger, calculates the control output Q _R. The calculation algorithm of the control element 24 is, for example, the following 1
It can be realized by the next delay element.

Here, K _Q is a forward gain and T _Q is a delay time constant. It was but connexion, Q _R is the _{constant, Q R = K Q · ε} Q ...... , and therefore (7), wherein when taking the code as in Figure 1, the receiving end reactive power Q _L is increased Then, the deviation epsilon _Q becomes small, the output _{Q R} is a small connexion, the receiving end reactive power _{Q L} is reduced, the deviation epsilon _Q increases output _{Q R} is large Do connexion, increase soot so the reactive power _{Q L} SVC1 Works. In this way, the reactive power control means 20 controls the receiving end reactive power Q.
_The SVC 1 is controlled so that _L becomes close to the set value Q _ref .

Next, select the two control outputs _Q V, the _{Q R} circuit 30
In selecting, the actual control output Q _C. The operation of selection is
The smaller the Q _V and _{Q R} and _{Q C.} In other _{words, Q C = Q R ← Q} R <Q V ...... (8) Q C = Q V ← Q R> Q V ...... and (8). By doing this, for example, Q _{ref is set} to SVC1
If you adjust to a value that can support about 80% of the capacity of
When the output of the backward impedance X is large SVC1 is, for example, that can be controlled system voltage at 50% or _{less, Q} R>
Q _V and Q _C = Q _{V and} AVR works.

Now, if the back impedance becomes small due to system operation, for example, the addition of a generator unit, etc., even if the output of the SVC 1 is set to 100% for the above-mentioned reason, the power receiving end voltage V
It is considered that _L cannot be controlled. In such a case, the output _{Q V} of the constant voltage control means 6 is _{saturated, Q} V> Q
_{R next,} since the Q C = _{Q R,} the constant reactive power control means 20 to function. Even if the back impedance X is large, if the fluctuation of the power receiving end voltage V _L is small, Q _V <
Q _R, and the constant voltage control means 17 to function.

The output Q _C selected in this way is input to the APPS 16, converted into an ignition pulse, and the thyristor valve 3 is phase-controlled, whereby a required reactive current is passed through the reactor 4.

Here, regarding the method of setting Q _ref , for example, when the power factor of the load is constant, the power consumption of the load is detected and Q _ref is set at a certain ratio.

In order to set the power reception rate to 1, Q _ref = 0. Etc. may be adopted.

〔The invention's effect〕

As described above, according to the present invention, even if an SVC having a limited equipment capacity is used, it is possible to cope with a variation in the short-circuit impedance of the system, and the operating state is not saturated, so that the SV
There is an effect that C can be effectively functioned.

Further, according to the present invention, since the operation mode can be changed autonomously without taking in new conditions from the outside, there is an effect that it is possible to flexibly cope with changes in system conditions. In addition, according to the present invention for the same reason as described above, there is an effect that the restriction of the installation point is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing the basic configuration of an SVC, and FIGS. 3 (a) and 3 (b) show the relationship between the voltage control function of the SVC and the rear impedance. FIG. 4 is an equivalent circuit and voltage vector diagram, and FIG. 4 is a block diagram showing a configuration of a general voltage fluctuation suppressing SVC. DESCRIPTION OF SYMBOLS 1 ... SVC, 2 ... Phase adjusting capacitor, 3 ... Thyristor valve, 4 ... Reactor, 5 ... Step-down transformer, 6 ... Reactive power generator, 7 ... Control device, 14 ... Subtractor, 15 ... AVR control element, 16 ... Automatic pulse phase shifter, 17 ... Constant voltage control means, 20 ... Constant reactive power control means, 22 ... Reactive power detector, 23 ... Subtractor, 24 ... Reactive power control element, 30 ... Output selection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-157223 (JP, A) JP-A-58-212328 (JP, A) JP-A-49-121154 (JP, A)

Claims (1)

[Claims] 1. A reactive power generator comprising a phasing capacitor connected to a power system, and a circuit including a phasing reactor and a switching element capable of controlling a current flowing through the phasing reactor in parallel connection. And a reactive power detection means for detecting reactive power from the voltage and current detected from the power system, and a control signal for driving the switching element based on a signal from the detected voltage or reactive power detection means. In the reactive power compensator including a controller for controlling the reactive power generator, the controller calculates a voltage control amount so that a deviation between the detected voltage and the set reference voltage becomes small. Constant voltage control means and constant reactive power control for calculating a reactive power control amount so that a deviation between the detected reactive power and the set reference reactive power becomes small. A reactive power compensating apparatus comprising: a means and a selecting means for selecting a smaller value of the voltage control amount and the reactive power control amount as a control signal of the switching element.