JPS63157617A - Control system of reactive power compensator - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to control of a reactive power compensator that compensates for reactive power generated by a load connected to a power system and thereby suppresses voltage fluctuations in the power system. Regarding the method.

[Conventional technology]

An example of this type of reactive power compensator is shown in FIG.

In the figure, 2 is a load connected to the power system via a transformer 1, 3 is a reactive power compensator that adjusts the reactive power by controlling the phase of the reactor current with a thyristor, and 4 is the load 2 and the compensator 3. This is a harmonic filter that removes harmonics generated by Further, 5 is a control device,
This detects the reactive power generated by the load 2 from the system voltage e detected by PT7 and the load current LL detected by C70, and controls the compensation device 3 to compensate for it.

As shown in FIG. 6, this control device 5 includes a reactive power detection circuit 8 that detects the reactive power QL of the load from the system voltage e and the load current iL, and the value of the reactive power QL detected by the detection circuit 8. and a pulse generator 9 that determines the firing phase of the thyristor of the reactive power compensator 3 based on this and outputs a firing signal.

[Problem that the invention seeks to solve]

In this way, the system voltage e detected by PT7 and C
The detection circuit 8 calculates the reactive power QL of the load 2 based on the load power iL detected by the compensator 70, and as a result, the pulse generator 9 controls the firing phase of the thyristor of the compensator 3.
In particular, if load 2 is a load that fluctuates rapidly, such as a steelmaking arc furnace or a welding machine, the reactive power detection value QL will pulsate due to waveform distortion and high-frequency waves of the load current, making it impossible to accurately compensate for reactive power. The problem arises that it cannot be done.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for controlling a reactive power compensator that eliminates the disadvantages of the conventional example and allows accurate compensation even in the case of a rapidly changing load.

[Means for solving problems]

In order to achieve the above object, the present invention controls the firing phase of the thyristor every half cycle based on the detected value of the reactive power of the load, adjusts the reactive power, and suppresses voltage fluctuations in the power system. In the compensation device, an amount proportional to the difference between the average reactive power value of a half cycle and the reactive power detection value at the time when the thyristor is controlled to fire within that half cycle is added as a detection error to the reactive power detection value. The gist of this is to

[Effect]

According to the present invention, the average value of reactive power is calculated every half cycle of the power supply frequency, and the difference between that value and the reactive power detected value at the time when the thyristor is controlled to fire within the half cycle is invalidated as a detection error. By adding it to the power detection value, detection errors can be corrected and detection errors that continuously occur due to waveform distortion and harmonics of the load current can be reduced.

〔Example〕

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

FIG. 1 is a block diagram showing the method of the present invention. As a configuration of the control device shown in FIG. From the reactive power detection value QL detected by the power detection circuit 8,
The error detection circuit 10 calculates the detection error QE, the detection error QE is added to QL in the adder 11, and the added value QL' is input to the pulse generator 9.

A specific circuit example of such an error detection circuit 10 is shown in FIG. 2. The reactive power detection value QL is inputted to an integrator 12 that integrates the half cycle period every half cycle, and It is input to a sample hold circuit 13a that samples the QLO value.

Then, in the subtracter 14, the output QLT of the sample and hold circuit 13a is subtracted from the output QLi of the integrator 12, and the value of the difference ΔQ is inputted to the sample and hold circuit 13h, and the value at the final point of the integration performed every half cycle is input to the sample and hold circuit 13h. The value ΔQSH of ΔQ is siped and further smoothed by a filter 15 to obtain a detection error QB.

In this calculation, the final value of integration for each half cycle is a value proportional to the average value of half cycles of QL, so if the difference ΔQ between QLi and QLT is sampled at the final point of integration, the detection error of reactive power can be obtained. It turns out.

Figure 3 shows the operation of the circuit in Figure 2, and the detection error Q
By adding B as a correction amount to the reactive power detection value QL, detection errors that continuously occur due to waveform distortion and harmonic components of iL are corrected, and reactive power compensation performance is improved.

In another embodiment of the present invention, two sets of error detection circuits 10a and 10b are provided as shown in FIG. 4, and the detection error QEP in the positive half cycle and the detection error QEN in the negative half cycle are separately detected. The changeover circuit 16 selects QEP for the positive half cycle and QEN for the negative half cycle, and adds them as correction amounts in the adder 11.

In this way, when detection errors occur unevenly in each of the positive and negative half cycles, it is possible to appropriately correct the errors.

[Effects of the Invention] As described above, the method for controlling a reactive power compensator of the present invention corrects detection errors using waveform distortion and harmonics contained in the load current, and improves the compensation performance of the reactive power compensator. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the control method for the reactive power compensator of the present invention, FIG. 2 is a block diagram showing an example of the error detection circuit same as the above, and FIG. 3 is an explanatory diagram of the operation of the circuit shown in FIG. 2. FIG. 4 is a block diagram showing another embodiment of the present invention, FIG. 5 is an explanatory diagram of a reactive power compensator, and FIG. 6 is a block diagram showing a conventional method. 1... Transformer 2... Load 3... Reactive power compensator 4... Harmonic filter 5... Control device
6...CT7...PT 8...
・Reactive power detection circuit 9...Pulse generator 10...
・Error detection circuit 10a, 10b...Error detection circuit 11...Adder 12...Integrator 13a,
13b...Sample hold circuit 14...Subtractor 15...Filter 16...Switching circuit

Claims (1)

[Claims] In a reactive power compensator that controls the firing phase of a thyristor every half cycle based on the detected value of the reactive power of the load to adjust the reactive power and suppress voltage fluctuations in the power system, the half-cycle reactive power Reactive power compensation characterized in that an amount proportional to the difference between the average value and the reactive power detection value at the time when the thyristor is controlled to fire within the half cycle is added to the reactive power detection value as a detection error. How to control the device.