JPH10243563A - Reactive power compensator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to steplessly improve the load power factor of a power system by causing an inverter connected to the secondary winding of a transformer to output a desired voltage in phase with or in opposite phase to the fundamental-wave voltage of the power system. SOLUTION: An inverter 24 uses six sets of bridge-connected semiconductor switch circuits wherein a gate turn-off thyristor and a diode are inverse-parallel- connected and contains a smoothing capacitor on the direct current side. The output of the inverter 24 is connected with one end of the secondary winding of each transformer 23, and the other end of the secondary winding of each transformer 23 are parallel-connected. Because of this circuitry, the load power factor of a power system 1 can be steplessly improved at high speed by adjusting voltage applied to a capacitor or reactor through the transformer 23 and the inverter 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive power compensator for improving a load power factor of a power system.

[0002]

2. Description of the Related Art FIG. 5 is a main circuit configuration diagram showing a conventional example of this type of reactive power compensator, wherein 1 is a power system, 2 is a load of the power system 1, and 3 is a load from the power system 1 to the load 2. This is a reactive power compensator for improving the power factor of supplied power. FIG.
The reactive power compensating device 3 shown in FIG. 1 detects a circuit breaker 11 to 13, a capacitor 14 to 16, and a load power factor of a power system 1 (not shown) to switch on and release each of the circuit breakers 11 to 13. It is composed of

[0003] The operation of the reactive power compensator 3 is performed by using a known technique, and a description thereof will be omitted.

[0004]

According to the conventional reactive power compensator 3, the load power factor of the power system 1 is detected and one or more of the circuit breakers 11 to 13 are turned on and released. Therefore, there is a problem that the load power factor is only improved stepwise, the switching frequency of switching on and off of each of the circuit breakers 11 to 13 is restricted, and the switching speed is slow.

[0005] An object of the present invention is to solve the above-mentioned problems, and further to convert the existing reactive power compensator to a conventional technique.
An object of the present invention is to provide a reactive power compensator that can perform an additional operation to improve a load power factor of a power system in a stepless manner.

[0006]

According to a first aspect of the present invention, a primary circuit of a transformer and a series circuit of a capacitor are connected in parallel to a power system, and an output of an inverter is connected to a secondary winding of the transformer. The inverter is a reactive power compensator that outputs a desired voltage in phase or opposite phase to the fundamental voltage of the power system.

According to a second aspect of the present invention, a primary circuit of a transformer and a series circuit of a reactor are connected in parallel to a power system, and an output of an inverter is connected to a secondary winding of the transformer. A reactive power compensator that outputs a desired voltage that is in phase or opposite to the fundamental voltage of the system. According to this invention, the voltage applied to the capacitor or the reactor is adjusted by the transformer and the inverter, so that the load power factor of the power system can be improved steplessly and at high speed.

[0008]

FIG. 1 is a block diagram of a main circuit of a reactive power compensator according to a first embodiment of the present invention, wherein 1 is a power system, 2 is a load of a power system 1, and 4 is a power system. 1 is a reactive power compensator that improves the power factor of power supplied from 1 to the load 2. The reactive power compensator 4 shown in FIG.
, Capacitor 22, transformer 23, inverter 24
And an inverter control for detecting the load power factor of the power system 1 (not shown) and outputting the desired output voltage in the same or opposite phase as the fundamental wave voltage of the power system 1 based on the detected value. And a circuit.

FIG. 2 shows a detailed main circuit configuration diagram of the transformer 23 and the inverter 24 shown in FIG.
4 is, for example, a gate turn-off (GTO) as shown in the figure.
Six sets of semiconductor switch circuits in which a thyristor and a diode are connected in anti-parallel are used in a bridge connection, and a smoothing capacitor is provided on the DC side. The output of the inverter 24 is connected, for example, to one end of a secondary winding of each transformer 23, and the other end of each secondary winding of the transformer 23 is connected in parallel.

FIG. 3 shows the reactive power compensator 4 shown in FIG.
3 is an equivalent circuit and a vector diagram for explaining the operation of FIG. FIG. 3A shows the voltage vector of the power system 1 as V _L , the voltage vector as viewed from the primary side of the transformer 23 of the inverter 24 as V _INV, and the voltage and current vectors of the capacitor 22 as V _C and i. ₇ is an equivalent circuit of the reactive power compensating device 4 denoted by _C.

[0011] In FIG. 3 (b), in the opposite phase to V _INV against V _L by adjusting the output voltage of the inverter 24, the operation state of the V _C has been smaller than the V _L to reduce the i _C Is shown. Similarly, in FIG. 3 (c), in the same phase of the V _INV against V _L by adjusting the output voltage of the inverter 24, the operation state of the V _C increased i with greater than V _{L C} Is shown.

As is clear from the vector diagram of FIG. 3 (b, c), V _INV and i _C are orthogonalized and the inverter 24
From now on, by operating to always supply only the reactive power, the inverter 24 does not need a DC power supply,
As shown in FIG. 2, only a smoothing capacitor is required. Or
Instead of the smoothing capacitor, a rectified power supply small enough to compensate for the circuit loss of the inverter 24 may be used.

The reactive power compensator 4 is useful when the load 2 has a delayed power factor. FIG. 4 is a diagram showing a main circuit configuration of a reactive power compensator according to a second embodiment of the present invention.
Reference numeral 2 denotes a power system, reference numeral 2 denotes a load of the power system 1, and reference numeral 5 denotes a reactive power compensator for improving the power factor of power supplied from the power system 1 to the load 2. The reactive power compensator 5 shown in FIG. 4 detects a breaker 31, a reactor 32, a transformer 33, an inverter 34, and a load power factor of the power system 1 (not shown). The output voltage includes an inverter control circuit that outputs a desired voltage having the same or opposite phase as the fundamental wave voltage of the power system 1.

The transformer 33 and the inverter 34 of the reactive power compensator 5 shown in FIG. 4 have the same configuration as the transformer 23 and the inverter 24 of the circuit of the first embodiment shown in FIG.
This reactive power compensator 5 is useful when the load 2 has a leading power factor.

[0015]

According to the present invention, by connecting a series circuit of a capacitor or a reactor and a transformer in parallel to a power system and adjusting the voltage applied to the capacitor or the reactor by the transformer and the inverter, the power The load power factor of the system can be improved steplessly and at high speed.

In particular, it is possible to provide a new reactive power compensator capable of improving the load power factor of a power system in a stepless manner by modifying or adding an existing reactive power compensator according to the prior art.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main circuit of a reactive power compensator according to a first embodiment of the present invention;

FIG. 2 is a partial detailed circuit configuration diagram of FIG. 1;

FIG. 3 is a view for explaining the operation of FIG. 1;

FIG. 4 is a configuration diagram of a main circuit of a reactive power compensator according to a second embodiment of the present invention;

FIG. 5 is a main circuit configuration diagram of a reactive power compensator showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power system, 2 ... Load, 3-5 ... Reactive power compensator,
11-13: Circuit breaker, 14-16: Condenser, 21 ...
Circuit breaker, 22: condenser, 23: transformer, 24: inverter, 31: circuit breaker, 32: reactor, 33: transformer, 34: inverter.

Claims (2)

[Claims] 1. A series circuit of a primary winding of a transformer and a capacitor is connected in parallel to a power system, and an output of an inverter is connected to a secondary winding of the transformer. A reactive voltage compensating device that outputs a desired voltage having the same phase or opposite phase. 2. A series circuit of a primary winding of a transformer and a reactor is connected in parallel to a power system, and an output of an inverter is connected to a secondary winding of the transformer. A reactive voltage compensating device that outputs a desired voltage having the same phase or opposite phase.