JPS6399728A - Reactive power compensating controller - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention compensates for reactive power generated from fluctuating loads connected to a power grid, such as arc furnaces, welders, steel rolling equipment, etc., and reduces the grid voltage. The present invention relates to a control device for controlling a thyristor phase control reactor type reactive power compensator (hereinafter also simply abbreviated as TCR) that suppresses fluctuations in

[Conventional technology]

Figure @4 is a block diagram showing this type of compensation system. In the same figure, 1 is a TCR control device, 2IdTCR13
is a filter capacitor, and 4 is a load. In this system, each reactive power (var) of the system, load, TCR, and filter capacitor is expressed as QSr QL r
QTCR and Q. When, QS=QL+QTCR+QC? .

The TCR is controlled to fully compensate for the reactive power so as to satisfy the following relationship, and the voltage drop due to the system impedance Xs is suppressed. At this time, especially for a load such as an arc furnace that produces a sharply fluctuating noise, it is necessary to predict the reactive power of the load every half cycle and control the TCR at high speed.

5 is a block diagram showing a conventional example of the reactive power compensation control device JR, and FIG. 6 is an explanatory diagram of its operation.

In the 1aVi sample hold circuit of Fig. 5, Fig. 6 (
The system voltage e at the zero point of the load current IL as shown in a).

This value is as shown in Figure 6 (b).
si port Cp (B: Effective value of system voltage.

ψ: power factor angle). 12 is an integrator, and the current IL in FIG.
When is close to a sine wave, it is proportional to its effective unity. Therefore,
When these brushes are multiplied by the multiplier 13, it becomes (see Fig. 6 (d)), and by sampling this value at the time of θi in the sample and hold circuit 1b as shown in Fig. 6 (e), The reactive power of the load can be obtained in advance. Reference numeral 14 denotes a compensation characteristic adjustment circuit, which is a circuit for determining compensation characteristics such as compensation sensitivity with respect to the obtained predicted value of reactive power QL, and according to its output, the pulse generator 1
5, the ignition signal g of the desired control phase (see Fig. 6 (f))
is configured to obtain.

[Problem that the invention seeks to solve]

However, according to this type of control device, the prediction accuracy is high when the load current is close to a sinusoidal waveform, but the prediction error becomes large when the load current contains many harmonics, such as in an arc furnace. There are drawbacks. Figure 7 is for explaining this.If the waveform distortion near zero current (period of θi) is large, the prediction error will be large, and in this example, the current integral value will be detected large, so the actual IL From the fundamental wave effective value, it is predicted that This shows a case where the l value becomes large. It goes without saying that the opposite case may occur depending on the way the waveform is distorted.

Therefore, it is an object of the present invention to reduce prediction errors of load reactive power due to such waveform distortion and to provide a control device with high prediction accuracy.

[Means for solving problems]

A multiplier that multiplies the load by current and grid voltage to obtain instantaneous reactive power and instantaneous active power, respectively, and load 'ai! t
It is obtained by dividing the total sum of the integral value of the instantaneous value of reactive power from the zero point and 1/2 of the instantaneous value of active power by a function θ proportional to the time from the zero point of the load current, and further integrating the value from the zero point of the current. A calculation circuit that calculates the first function and a function generator that generates a second function related to the phase control angle that determines the reactive power generated by the reactive power compensator are provided, The function obtained by dividing by θ is compared with the second function, and when the two become equal, a firing signal for firing the thyristor of the reactive power compensator is generated.

[Effect]

Load number one! The instantaneous value p of active power obtained by multiplying the current IL and the grid voltage e□, and the voltage e delayed by 90 degrees from the load current IL and the grid voltage. The reactive current (θ is the angle from the zero point of the load current) obtained by By performing control using the value obtained by integrating the instantaneous reactive power value q,
The harmonic components contained in the load current are averaged to improve the prediction accuracy of reactive power. The method to obtain the ignition signal is as follows:
There is a method of obtaining pulses under the condition that the phase control that determines the reactive power generated by the compensator is equal, and a method of performing all pulses under the condition.

[Embodiments of the invention]

The TCR control relational expression for compensating the reactive power of the load is expressed as follows.

KF (QL-QLO)+QTcR=K (constant)...
... (1) Here, KF is the compensation sensitivity, QL is the reactive power of the load, and QLO is the non-variable component (base portion) of QL.
, QTCR is the reactive power generated by TCR. Usually, the CRR is selected as -Q (rated reactive power of TCR), and the above equation (1) becomes... (2). Here, if it is expressed as a control angle β starting at a phase of 90° from the zero point of the QTCR system voltage,...
(3) It becomes like this. Here, βm10 is the minimum control phase angle, and at this phase TCR generates the rated reactive power QTCRR.

Substituting equation (3) into equation (2), we get KF(QL-QLo)-f(β) -old
-(4).

10,000, considering the fundamental wave component of load 'iii flow iL, 1L=
i engineering Lsiflθ ・・・・・・ (
5) (θ is the electrical angle from the zero load current point) If expressed as, the instantaneous active power p and the instantaneous reactive power fm
q is expressed as shown in the following equation.

p−J”j Eo sin (ψ+θ) X J”i
IL sinθ"'BOIL(cO59'"(9'
+20) ・・−・−(6)q = Ji E
□ sin (ψ+θ−90°) X (2I, sin
θ−golL(siaψ−5in (ψ+2θmonth)
...... (For example, Eo is the effective value of the system voltage, and ψ is the power factor angle. Also, the integral value of q from the current zero point is 1.1 = EoIt(θ5illψ1−ωS( ψ+2θ72 c
osψ)... (8)

(8) Samurai T
tsin ψ×θ ・−・−・−(9) is obtained. Since the load reactive power QL is QL-EQIL sin ψ, the following relationship holds: fqdo p - QI, Xθ. Therefore, it is expressed as . This negative value has a pulsating component due to harmonics contained in the load current, so if it is further integrated and averaged by dividing by θ, it becomes αυ. When the predicted value of this Q'kQL is substituted into Q in equation (4), it becomes . . . α2. Therefore, by creating two functions on the left side and the right side and finding their intersection, the control phase for TC that satisfies Equation 13 will be obtained.

FIG. 1 is a block diagram showing an example of the present invention, and is for concretely realizing the above-mentioned functions. Also, the second
The figure is a waveform diagram of each part for explaining the entire operation.

In Fig. 1, the multipliers 13a and 13b are shown in Fig. 2 (A).
A voltage e that is in phase with the first load current and the grid voltage shown in . ,
From the voltages e and o whose phase is delayed by 90 degrees, the instantaneous reactive power value q and the instantaneous active power value p as shown in Fig. 2 (b) are obtained.
It is used to calculate.

Then, the output q of the multiplier 13a is input to the integrator 12a to obtain a signal f-fqdθ (see FIG. 2 (c)), and the output p of the multiplier 13b is input to the proportional amplifier 16a to adjust the gain. After obtaining the signal h=”p (see FIG. 2 (c)), the adder 17a adds them together to obtain the signal 1−fqdθ+
2p (see FIG. 2 (c)) is calculated. On the other hand, integrator 1
2b and the voltage setting device 19a are circuits for obtaining a time function θ from the zero point of the load current, and create θ by integrating the voltage set by the setting device 19a from the zero point of the current. This signal θ
The signal i (/qdθ+2 p ) is divided by the divider 18a, and QL
is integrated by an integrator 12C and divided by θ by a divider 18b to calculate QL' as shown in FIG. 2(E).

After that, the adder/subtracter 17b subtracts the value of QLO set by the voltage setter 19b, and the proportional amplifier 16b subtracts the value of QLO set by the voltage setter 19b.
After multiplying by F, input it to the comparator 21. The function f(β) generated by the function generator 20 is input to the other input of the comparator 21, and the configuration is such that a firing signal is obtained at the point where both inputs become equal.
The firing signal q of the control phase that satisfies the relational expression of Eq.
) can be obtained.

FIG. 3 is a block diagram showing another embodiment of the present invention.

This is calculated by adding the first θ to both sides of the above formula 02,...
The ignition signal is obtained by transforming the equation into αJ, creating two functions on both sides of this equation, and comparing the two. The basic idea is exactly the same as that shown in FIG. 1, and the calculation of formula 03 is simply replaced with a specific circuit, so detailed explanation will be omitted.

〔Effect of the invention〕

According to this invention, the prediction based on the integral value of the load current IL for a certain period is stopped, and the reactive power QIJ of the load is calculated from the continuous integral value of the reactive power q and the active power p, and it is further divided into shares to calculate the average f. = and obtains an ignition signal that satisfies the TCR control conditions based on the value immediately before thyristorlar control, reducing the influence of harmonics contained in the load current and reducing load invalidation. The advantage is that the prediction accuracy can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of this invention, Fig. 2 is a waveform diagram of each part to explain its operation, Fig. 3 is a block diagram showing another embodiment of this invention, and Fig. 4 is invalid. FIG. 5 is a block diagram showing a conventional example of a reactive power compensation control device, FIG. 6 is a waveform diagram of each part to explain its operation, and FIG. 7 is a block diagram showing a general example of a power compensation system. FIG. 3 is an explanatory diagram for explaining a prediction error of reactive power due to waveform distortion. Code explanation 1... Control device for reactive power compensation, 2...
- Reactive power compensator 1 (TCR), 3...Filter capacitor, 4...Load, 1st a #1b
...Sample and hold circuit, 112a#12
b, 12C...Integrator, 13, 13a, 13b
, 13c, 13d... Multiplier, 14... Compensation characteristic adjustment circuit, 15... Pulse generator, 16a
, 16b...proportional amplifier, 17a, 17
b--Adder/subtractor, 18a, 18b...
・Divider, 19a, 19b... Voltage setting device, 2
0...Mi generator, 21...Comparator. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyota Matsuzaki 12 1 [Figure 3 Figure 2 Figure 4 Figure 4 5r! J

Claims (1)

[Scope of Claims] 1) A control device for controlling a thyristor phase control type reactive power compensator provided to compensate for reactive power generated by a fluctuating load connected to an electric power system and suppress its voltage fluctuation. A multiplier that multiplies the load current and the grid voltage to obtain the instantaneous value of reactive power and instantaneous active power, respectively, and a multiplier that multiplies the instantaneous value of reactive power and the instantaneous value of active power from the zero point of the load current, and
an arithmetic circuit that calculates a first function obtained by dividing the sum of 2 and 2 by a function θ proportional to the time from the zero point of the load current and further integrating this from the zero point of the current; a function generator that generates a second function related to a phase control angle that determines reactive power; and a function that is obtained by dividing the first function by a function θ and the second function are compared. A control device for reactive power compensation, characterized in that when the two become equal, a firing signal for firing the thyristor is generated. 2) In the reactive power compensation control device according to claim 1, when the first function and the function obtained by multiplying the second function by a function θ are compared and the two become equal. A control device for reactive power compensation, characterized in that it emits an ignition signal. 3) In the reactive power compensation control device according to claim 1, the load reactive power is calculated from a function obtained by dividing the first function by a function θ to be compared with the second function. A control device for reactive power compensation, characterized in that a predetermined value corresponding to a non-variable component (base component) is subtracted. 4) In the reactive power compensation control device according to claim 2, the function to be compared with the function obtained by multiplying the second function by a function θ is calculated from the first function. A control device for reactive power compensation, characterized in that a value obtained by multiplying a predetermined value corresponding to a non-variable component (base component) by a function θ is subtracted.