JPH0670466A - Controller of harmonic reactive power compensator - Google Patents

Abstract

PURPOSE:To protect a power converter in a harmonic reactive power compensator which compensates the harmonic current and reactive power of a load from an overload quickly without degrading the performance regardless of a load state. CONSTITUTION:A converter capacity is operated by a converter power operator 7 from a system voltage which is the output of a voltage detector 4 which detects the voltage of a power system 1 and a power converter output current which is the output of a current detector 6 which detects the output current of the power converter. If the capacity exceeds a rated capacity, the gain of a detected load current value which is the output of a current detector 5 which detects the load current is varied by a variable gain circuit 8 to avoid the saturation of a signal and, further, a compensation current command Ic* which is the output of a compensation current operator 10 which operates the compensation current command Ic* is limited to a value corresponding to the rated capacity to protect the power converter 3 from an overload.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit of a harmonic reactive power compensator for compensating a harmonic current and a reactive power flowing into a load facility by a power converter.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing the configuration of a conventional harmonic reactive power compensator for compensating for a harmonic current and reactive power. In FIG. 2, 1 is a power system, 2 is a load connected to the power system, 3 is a power converter that outputs a compensation current to compensate the harmonic current and reactive power of the load, and 4 is the voltage of the power system. Is a voltage detector for detecting a load current, 5 is a current detector for detecting a load current, 6 is a current detector for detecting an output current of the power converter 3, and 9 is a load current IL detected by the load current detector. Limiter circuit, 10 is a compensation current calculation circuit that calculates a compensation current command Ic ^* from the system voltage detection value Vs detected by the voltage detector 4 and the load current detection value IL detected by the current detector 5, and 11 is a compensation A limiter circuit for limiting the current command Ic ^* , 12 is an addition circuit, 13 is a current control circuit, and 14 is an ignition circuit.

In this harmonic reactive power compensating device, the harmonic current of the load and the reactive power are detected by the compensation current calculation circuit 10 from the system voltage Vs detected by the voltage detector 4 and the load current detection value IL passing through the limiter circuit 9. Compensation current command Ic ^*
Is calculated, and the control pulse is ignited by the current limiting circuit 13 so that the current Ic of the power converter 3 detected by the current detector 6 follows the compensation current command Ic ^* via the limiter circuit 11.
And a gate signal is given to the power converter 3 by the ignition circuit 14.

[0004]

As described above, in the conventional control circuit of the harmonic reactive power compensator, the protection when the power converter is overloaded is performed by the two limiter circuits 9 and 11. . The limiter circuit 9 limits the peak value when the load current detection value IL is too large to prevent excessive inflow to the compensation current calculation circuit, and the limiter circuit 11 limits the peak value when the compensation current command Ic ^* is too large. The operation is performed by limiting and preventing the power converter 3 from outputting an excessive current. However, with the limiter circuit, the power converter 3
Since the peak value of the output current of is only limited, there is a risk of continuous overload, and a new harmonic current may be generated. Also in the limiter circuit 9, when the peak value of the load current detection value IL is limited and saturated, the power converter 3 still generates a new harmonic current. If the signal level is lowered to avoid saturation, there is a problem that the resolution deteriorates.

The present invention has been made to solve the above problems, and when the capacity of the power converter exceeds the rated capacity, the gain of the load current detection value IL is varied to saturate the load current. It is intended to prevent the harmonic current and the reactive power equivalent to the rated capacity from being generated without generating a new harmonic current and the reactive power.

[0006]

The present invention has been made in view of the above points, and in particular, a converter power calculation circuit for calculating the converter capacity of a harmonic reactive power compensator,
Provide a variable gain circuit that changes the gain of the load current IL,
When the load is large and the converter capacity exceeds the rating, reduce the gain of the load current detection value IL to prevent signal saturation and always compensate only for the reactive power and harmonic current components equivalent to the rated capacity even in the case of overload. It is what More specifically, a converter power calculation circuit that calculates the converter capacity from the system voltage Vs and the compensation current Ic, and if the converter capacity exceeds the rated value, the load current detection value IL It is provided with means for varying the gain.

[0007]

In the present invention, the capacity of the power converter 3 is calculated, and when the capacity exceeds the rated capacity, the gain of the load current detection value IL is reduced, and in order to always compensate the harmonic current and the reactive power corresponding to the rated capacity, any load Even in the state, the power converter can be promptly protected from overload without impairing the performance.

[0008]

1 is a block diagram showing the structure of an embodiment of the present invention, and the same reference numerals as those shown in FIG. 2 denote the same parts.

The converter power calculation circuit 7 calculates the converter capacity from the system voltage detection value Vs which is the output of the voltage detector 4 and the converter current detection value Ic which is the output of the current detector 6. When the converter capacity exceeds the rated capacity, the variable gain circuit 8 lowers the gain of the load current detection value IL so that it corresponds to the rated capacity, outputs it to the compensation current calculation circuit 10 via the limiter circuit 9, and outputs the compensation current command. Ic ^* is calculated. Compensation current command Ic ^*
Is output to the adder 12 via the limiter circuit 11 and added to the output current Ic of the power converter 3 which is the output of the current detector 6,
The current control circuit 13 outputs a signal that follows the compensation current command Ic ^* to the ignition circuit 14, and the ignition circuit 14 gives a gate signal to the power converter 3.

[0010]

As described above, according to the present invention, the capacity of the power converter is calculated by the compensation power calculation circuit, and when the capacity exceeds the rated capacity, the load current is adjusted so that the compensation current command corresponding to the rated capacity is obtained. Signal saturation is prevented by lowering the gain of the detection value IL, and compensation is promptly made for the rated capacity equivalent without generating new harmonic current, so there is no loss of performance even when overloaded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a control circuit of a harmonic reactive power compensator of the present invention.

FIG. 2 is a block diagram showing the configuration of a conventional harmonic reactive power compensator for compensating for harmonic current and reactive power.

[Explanation of symbols]

1 Power system 2 Load connected to power system 3 Power converter that outputs compensation current to compensate harmonic current and reactive power of load 4 Voltage detector that detects voltage of power system 5 Detects current of load Current detector 6 Current detector to detect output current of power converter 7 Converter power calculation circuit 8 Variable gain circuit 9 Limiter circuit to limit load current IL 10 Compensation current calculation circuit to calculate compensation current command Ic ^* 11 Compensation Limiter circuit that limits the current command Ic ^* 12 Addition circuit 13 Current control circuit 14 Firing circuit

Claims (1)

[Claims] 1. A harmonic reactive power compensator for compensating a harmonic current and reactive power of a load by a power converter,
A converter power calculation means for calculating the capacity of the power converter, and means for varying the gain of the load current detection value when the capacity exceeds the rated capacity are provided, prevent saturation of the load current detection value, and compensate the compensation current command value. A control circuit for a harmonic reactive power compensator, which is limited to a rated capacity and protects the power converter promptly from overload.