JP2581459Y2 - Control method of voltage fluctuation suppression device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a voltage fluctuation suppressing device of a voltage control system for controlling a reactive power compensator (hereinafter referred to as SVC) installed in an AC power system by detecting only a system voltage. About.

[0002]

2. Description of the Related Art An SVC controls the phase of a thyristor control reactor (hereinafter, referred to as TCR) connected to a power system, supplies reactive power to the system to offset the reactive power fluctuation of a load, and supplies the system with voltage fluctuation. Suppress. In the control of the SVC, generally, a reactive power Q of a load is calculated from a system voltage and a load current, and the calculated reactive power Q is used as an open-loop control signal.
It is performed by control.

However, as shown in FIG. 4, when this SVC is installed at the receiving point from the substation 0 and is operated for the purpose of suppressing the fluctuation of the receiving voltage Vl, the above-mentioned Q control cannot be performed for the following reasons. is there.

[0004] As shown in FIG. 1, the load A of another customer is placed on the power receiving line (substation bus) 01 of the substation 0.
B,... Are connected, and the reactive power of this load fluctuates steeply and irregularly like an arc furnace, causing voltage fluctuation. In this case, the customer who has installed the SVC cannot easily obtain the load current of another customer and cannot detect the reactive power of the load required for Q control.
It suppresses only the voltage fluctuation on the basis of the _l voltage control method (AV
R control).

Next, the equipment configuration of the above-mentioned voltage control system,
The operation will be described. In power system of FIG 4, 0 is the substation power E _s, expressed as an infinite bus. 01
The substation supply E _S and the power supply side Inpi - a connected substation Buss through dance X _L0, other consumer loads A, B, ... are connected through the power receiving transformer T _R.

[0006] The part surrounded by the dashed line N is the equipment of the customer who has installed the SVC. The customer is the line from the substation Buss 01 Inpi - receiving power at the receiving transformer 1 (T _R) through dance X _L1, feeding the customer load 3 which is connected to the customer load ugly 2. X _L2 is the line impedance of the consumer load bus 2.

[0007] The SVC adds TC load to the customer load bus 2.
R and a filter (hereinafter referred to as FC) are connected in parallel. TCR is composed of an inverse-parallel connected thyristors 4 high impedance transformers, etc. of the reactor X _L3 Prefecture,
The FC comprises a harmonic filter capacitor 5 and a small-capacity reactor 6 that absorbs harmonics by a series circuit of the capacitor 5.

The voltage control of the SVC is performed by a voltage transformer PT
By, taken out the system voltage Vl from the primary side of the power receiving transformer 1 (T _R), it is performed as a reference.

[0009] 7 is a voltage detection circuit, and converts the system voltage V _l to a DC detection value V _in effective value corresponding. Reference numeral 8 denotes a PLL circuit that generates a power supply synchronization signal from the system voltage _Vl . Reference _numeral 9 denotes a reference voltage generator that outputs a target reference voltage _Vref . 1
0 by the subtractor outputs a difference between the DC detection value V _in and the target reference voltage _{V ref (V ref -V in)} . Reference numeral 11 denotes a voltage controller that adjusts the response speed and sensitivity of AVR control, and has K ₁ / (1 + ST ₁ ) as a transfer function. Numeral 12 denotes a function circuit, which linearly converts the control signal so as to correspond to the relationship between the firing phase angle β of the _TCR and the generated reactive power Q _TCR .
A pulse generator 13 generates positive and negative trigger pulses from the output of the function circuit 12 based on the power supply synchronizing signal, and outputs the pulses to the gates G ₁ and G ₂ of the TCR.

[0010] The above-mentioned SVC control device has a DC detection value V
_in (system voltage _Vl ) with respect to the target reference voltage _Vref
It is input to the voltage controller 11 and its proportional integral output
_Is determined. by this,
DC detection value V _in the (system voltage V _l) to follow the target reference voltage V _ref, customer load Buss 2 voltage variation [Delta] V (%) ≒%
suppress z.

[0011]

The above-mentioned AVR control is feedback control for controlling the phase of the TCR with the integrated output of the voltage controller 11 having a first-order lag element. Therefore,
It is necessary to increase the first-order lag element (time constant) for control stabilization, and sharp voltage fluctuations (several cycle fluctuations)
Cannot be reflected on the control signal to be suppressed. Therefore, it is impossible to suppress steep and irregular voltage fluctuations as in the above-described arc furnace.

This will be further described with reference to a transfer function. The transfer function G (S ₁ ) of the voltage controller 11 that determines the response speed of the AVR control is

(Equation 2)

Hereinafter, a specific example will be described. Since% Z of the system is now equal to ΔV, if a normally required voltage control constant (AVR) steady-state deviation (ε) = ΔV / _GL (%) is targeted,

Loop GAIN ( _GL ) = ΔV / ε ≒ 10 times Loop time constant (τ _L ) = T ₁ / _GL ≦ 50 msec (about 3 cycles / 60 Hz).

As described above, the response time (τ _L ) of the normal AVR control system loop is about 50 msec (the system becomes unstable if a response speed less than this is required), and can be understood from FIG. As described above, the effect of improving steep and irregular voltage fluctuation (flicker) of an arc furnace or the like cannot be expected.

Therefore, the present invention provides a control method of SVC which can also obtain such an effect of reducing flicker.
An object of the present invention is to provide the above-described condition, that is, in a case where a current of another consumer load is not obtained and compensation is performed only by detecting a voltage signal.

[0017]

According to the voltage detection type SVC control system provided by the present invention, only the system voltage is used as an input signal, and the reactive power supplied from the thyristor control reactor to the system is increased or decreased to control the system voltage fluctuation. In the voltage fluctuation suppression device that suppresses the above, the difference between the detected system voltage and the reference voltage is passed through a voltage controller represented by a transfer function G ₁ (S) = K ₁ / (1 + ST ₁ ), and the output is relatively compared. As a control signal to suppress slow voltage fluctuations, the detected system voltage is applied to the thyristor control reactor at the same time.

(Equation 3) However, ST ₀ <ST ₂ <ST ₃ <ST ₁ , K ₂ << K ₁ ST ₀ : A flicker is suppressed by passing the output through a ΔV control circuit expressed by a response speed of a voltage detection circuit for detecting a system voltage. The control signal to be added is added to the output of the voltage controller and supplied to the thyristor control reactor.

[0018]

In the above configuration, since the .DELTA.V control circuit can detect only the flicker component at high speed, the voltage fluctuation of the flicker level remaining after suppressing the slow voltage fluctuation can be suppressed by the AVR control with the same responsiveness as an open loop. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is to compensate for a sharp voltage fluctuation by using an AVR control circuit together with a .DELTA.V control circuit. That is, as shown in FIG. 1, in a conventional voltage control type SVC provided with only a conventional AVR control circuit, a .DELTA.V detection circuit capable of extracting only a steep voltage fluctuation component as a control signal as a .DELTA.V control circuit 14. Fifteen
And an adder 16 for adding the ΔV detection signal to the conventional AVR control signal.

The other parts of the ΔV control circuit 14 surrounded by the dotted line have already been described, and thus are denoted by the same reference numerals and will not be described. The ΔV detection circuit 15 for extracting the ΔV control signal is provided by the first
, A second integrating circuit 18 and a subtractor 19.

The first integrating circuit 17 is intended to take out the flicker components from the DC detection value V _in of the system voltage in response speed ST ₂ with a predetermined amplification factor K _2, the transfer function K ₂ / (1 + ST
₂ ). This circuit takes out flicker that cannot be detected by the voltage controller 11, so that its response speed is faster than that of the voltage controller (ST ₂ <ST ₁ ). Since the integration output includes a component whose cycle is longer than the flicker, the second integration circuit 18 and the subtractor 19 apply negative feedback to extract only the flicker component. For this purpose,
The response speed of the transfer function 1 / (1 + ST ₃ ) of the second integration circuit 18 is set to (ST ₃ > ST ₂ ).

The response of the entire control system obtained by adding the ΔV control circuit 14 is represented by a transfer function as shown in FIG. 2, the transfer function of the voltage detecting circuit 7 for taking out the direct-current detection value V _in the system voltage V _l 1 / ST _0,
The transfer function of the voltage controller 11 is G as described above.
₁ (S) = K ₁ / (1 + ST ₁ ).

The transfer function G ₂ (S) of the ΔV detection circuit 15
Is that the transfer function of the first integration circuit 17 is K ₂ / (1 + S
T ₂ ), since the transfer function of the second integration circuit 18 that performs negative feedback by the subtractor 19 is 1 / (1 + ST ₃ ),

(Equation 4) It is.

The equation of the transfer function G ₂ (S) indicates that the ΔV detection circuit 15 is a secondary band-pass filter. Therefore, now, the loop GAIN of the system
When operated at ( _GL ) = 1, .DELTA.Q / .DELTA.V is controlled in an open loop, and a high-speed response is possible. That is, it can be expected that the output ΔQ of the ΔV detection circuit 15 compensates for voltage fluctuation due to voltage flicker.

Therefore, the conventional AVR control circuit compensates for relatively slow voltage fluctuations, and the ΔV control circuit 14 compensates for steep and irregular voltage fluctuations.

The respective circuit constants need to satisfy the relationship of (ST ₀ <ST ₂ <ST ₃ <ST ₁ , K ₂ << K ₁ ) in consideration of the stability of the system.

Next, as an example in which the .DELTA.V detection circuit 15 of the present invention can take out a steep voltage fluctuation as a control signal, the .DELTA.V control circuit 14 is connected to an actual system in which an SVC is installed. FIG. 3 shows the ΔV control signal thus obtained and a ΔQ detection signal obtained by connecting a general reactive power detection circuit (not shown) for Q control. Note that the control constant of the ΔV detection circuit 15 used in this measurement example is τ _L
≒ About 15 msec, G _L Ｇ1 time.

As can be seen from the comparison of the data in FIG.
The control signal follows the ΔQ detection signal. This means that voltage fluctuations caused by voltage flicker can be compensated only by ΔV control.

[0029]

According to the present invention, the AVR control circuit that suppresses a slow voltage fluctuation has a ΔΔ that enables high-speed detection.
By combining the V detection circuit, it is also possible to compensate for the steep voltage fluctuation (flicker) remaining only by the AVR control.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a voltage detection type SVC controller showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a portion related to a response speed of the circuit of FIG. 1 in a transfer function.

FIG. 3 is a diagram showing a comparison between a ΔV control signal output from the ΔV control circuit of the present invention and a ΔQ detection signal detected by a reactive power detection circuit for Q control in an actual power system.

FIG. 4 is a conventional voltage detection type SVC that performs only AVR control.
Circuit diagram showing control device

FIG. 5 is a diagram showing a correlation between a reactive power compensation rate and a flicker improvement rate with respect to response times t of different system loops when only AVR control is performed.

[Explanation of symbols]

 0 Infinity bus 01 Substation bus 1 Receiving transformer 2 Customer load bus 7 Voltage detection circuit 8 Power supply synchronization circuit 9 Reference voltage generation circuit 10 Subtractor 11 Voltage controller 12 Function circuit 13 Thyristor gate pulse generator 14 ΔV control circuit 15 ΔV detection circuit 16 adder 17 first integration circuit 18 second integration circuit 19 subtractor SVC reactive power compensator TCR thyristor control reactor FC filter

Claims (1)

(57) [Scope of request for utility model registration] As claimed in claim 1 reference only system voltage V _l, increase or decrease control the reactive power to be supplied from the thyristor controlled reactor to the system, in suppressing voltage fluctuation suppressing device voltage fluctuations in the system, the DC detection value of the system voltage V _l The difference between V _in and the target reference voltage V _ref is input to a voltage controller represented by a transfer function G ₁ (S) = K ₁ / (1 + ST ₁ ), and its output is suppressed to a relatively slow voltage fluctuation. as a control signal to, and at the same time given to the thyristor controlled reactor, the DC detection value V _in system voltage V _l, Equation 1] However, ST ₀ <ST ₂ <ST ₃ <ST ₁ , K ₂ << K ₁ ST ₀ : Input to the ΔV control circuit expressed by the response speed of the voltage detection circuit for converting the system voltage _Vl to DC, and output As a control signal for suppressing flicker, which is added to the output of the voltage controller and given to the thyristor control reactor.