JPH10210660A - Current compensator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a current limiting circuit, which limits the compensation of the harmonic current component or the reactive current component of a power system, when a load is less than a rated capacity as a circuit with a low cost and a simple construction. SOLUTION: A load current is detected by a current detector 10. The harmonic compensation object component of a power system is extracted by a compensation object current detection circuit 11 from the detection signal. A coefficient '1' is outputted, when the effective value of the compensation object component is less than a rated command value, and the effective value is outputted as the coefficient when the effective value exceeds the rated command value. The compensation object component is divided by the coefficient in a divider 18, to obtain a compensation current command signal. A current regulator 4 is controlled based on the compensation current command signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current compensator for supplying a compensation current for compensating a harmonic current or a reactive current component of a power system via a current regulator. In particular, the present invention relates to a current compensator to which a current limiting circuit for limiting compensation exceeding a rated capacity is added when a compensation current is large.

[0002]

2. Description of the Related Art This type of current compensator is disclosed in
No. 2621, and a block diagram thereof is shown in FIG. In FIG. 5, reference numeral 1 denotes a power supply of a power system L,
The load 2 is connected to the power system L. The power system L includes a current regulating device 4 and a reactance device 7 including a capacitor and a reactor, which are connected via a transformer 3 having an appropriate transformation ratio as required. The current regulating device 4 is composed of self-turn-off switching elements 5a, 5b... Such as IGBTs, bipolar transistors, MOSFETs, etc., and diodes 6a, 6b. And a bridge inverter.

A compensation current ic flowing through the current adjustment device 4 is detected by a current detector 13, and this detection signal is matched with a compensation current command signal ic 'via a control circuit 14 so that the deviation becomes zero. The device 4, ie the compensation current ic, is PWM controlled.

On the other hand, the current of the power system L is
, And a compensation target current detection circuit 11 extracts a compensation target harmonic or reactive power component current Ih from the detection output. The effective value A of the current to be compensated Ih is obtained, for example, by sampling the effective value detection circuit 15 at predetermined time intervals. The effective value A thus obtained is compared with a predetermined command value IR for commanding the device capacity of the coefficient setting device 30. In the coefficient setting unit 30, the effective value A output from the effective value detection circuit 15 and the rated value setting unit 31
Is input to the divisor terminal of the divider 33, and the high-priority circuit 32 inputs the rated command value IR to the divisor terminal of the divider 33.
The input of the rated command value IR to the dividend terminal 3
A coefficient K is obtained at the output of 3.

According to the coefficient setting device 30, when the effective value A is equal to or less than the rated command value IR, the rated command value IR is input to the divisor terminal of the divider 33, and the coefficient K becomes IR / IR = 1. When the effective value A exceeds the rated command value IR, the divisor terminal of the divider 33 supplies the effective value A of the effective value detection circuit 15 to the divisor terminal.
Is input, and the coefficient K becomes IR / A.

The coefficient K obtained in this manner is multiplied by a multiplier 1
7, and the multiplier 17 multiplies the compensation target current Ih obtained by the auxiliary current detection circuit 11 by the multiplier 17. That is, when the effective value A is equal to or less than the rated command value IR, the output signal I
c ′ is Ih × 1 = Ih, and the effective value A is the rated command value I
R, the output signal Ic ′ of the multiplier 17 becomes Ih
× IR / A. Then, a compensation current command signal ic 'corresponding to the device capacity obtained as the product is formed.

On the other hand, the compensation current ic compensated by the current adjusting device 4 and the reactance device 7
The detection signal is matched with the compensation current command signal ic ′, and the bridge inverter of the current regulator 4 is PWM-controlled via the control circuit 14 so that the deviation becomes zero, and the compensation current ic is controlled. Is done. In this way, even when the compensation capacity exceeds the rating of the device capacity, there is no limitation by the saturation element, so that the linearity is maintained and no extra harmonics are generated.

[0008]

However, the coefficient setting unit 30 needs to be constituted by a dividing circuit of K = IR / A, and there is a problem that the circuit is complicated and the cost is high.

[0009]

In order to solve the above-mentioned problems, the present invention according to claim 1 of the present invention provides a current adjustment for controlling a compensation current for compensating for a harmonic or a reactive power component of a power system. A device, a current detector for detecting a load current,
A compensation target current detection circuit that extracts a compensation target component of a harmonic or a reactive power component of the power system from the detection signal,
An arithmetic circuit for calculating an effective value, an average value, or a peak value of the component to be compensated to obtain an arithmetic value, and a time coefficient 1 which is equal to or less than a rated command value for instructing the rated value of the device capacity. A coefficient setting device that outputs the calculated value as a coefficient when the value exceeds the rated command value; a divider that divides the compensation target component by the coefficient to calculate a compensation current command signal; And a control device for controlling the current adjusting device so as to match the current command signal.

A load current is detected by a current detector, and this detection signal is extracted by a compensation target current detection circuit as a component to be compensated for a harmonic or reactive current component of the power system. An effective value, an average value, or a peak value of the component to be compensated is calculated by an arithmetic circuit to obtain a calculated value,
When the calculated value is equal to or less than a rated command value for instructing the rated value of the device capacity of the calculated value, the coefficient 1 is output. When the calculated value exceeds the rated command value, the calculated value is output as a coefficient. The component to be compensated is divided by the coefficient of the coefficient setting unit by the divider,
A compensation current command signal is calculated. Then, the current adjusting device is controlled such that the compensation current for compensating the harmonics or the reactive power component of the power system matches the compensation current command signal.

According to a second aspect of the present invention, a current output from a current power supply is detected by a current detector, and the detected signal is used to extract a harmonic or reactive power component of the power system by a current detection circuit for compensation. The current adjustment device is controlled based on the compensation target component that has been feedback-controlled so as to cancel the extracted signal.

According to the first aspect of the present invention, the current flowing to the load is detected. However, in the second aspect of the present invention, the current output from the power supply is detected, and the power system is detected by the current detection circuit for compensation. Is extracted, and a compensation target component that is feedback-controlled to cancel out the extracted signal is extracted. The current adjusting device is controlled based on the compensation target component.

According to a third aspect of the present invention, a power supply voltage is detected by a voltage detector, and the detected signal is used to extract a harmonic or reactive power component of a power system by a compensation target voltage detection circuit. The current compensator is controlled based on the compensation target component that is feedback-controlled so as to cancel.

A power supply voltage is detected by a voltage detector, and a harmonic signal or a reactive power component of a power system is extracted from the detected signal by a voltage detection circuit for compensation, and feedback control is performed so as to cancel the extracted signal. Extract the target component. The current adjusting device is controlled based on the compensation target component.

According to a fourth aspect of the present invention, there is provided a rated command value setting device in which the coefficient setting device commands a rated value of the device capacity, a buffer for amplifying the rated command value, an output of the buffer and the calculated value. And an operational amplifier for comparing and amplifying the operational amplifier, and an OR circuit provided at the output of the buffer and the operational amplifier.

When the calculated value is equal to or less than the rated command value, the coefficient 1 is output from the buffer for amplification and is output to the output of the coefficient setting unit. When the calculated value exceeds the rated command value, the output of the buffer is input to the operational amplifier. Then, the calculated value is compared with the calculated value, and the calculated value is output to the output of the coefficient setting device.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a current compensator according to the present invention will be described with reference to FIG. The difference between the current compensating device in the present embodiment and the above-described prior art is that the coefficient 1
When the rated command value IR is exceeded, the coefficient setter 30 that outputs a coefficient for dividing the rated command value by the effective value A is replaced by a coefficient 1 when the effective value is equal to or less than the rated command value IR. When the command value is exceeded, a coefficient setting unit 1 that outputs an effective value
6, and the compensation target current Ih of the compensation target current detection circuit 11 instead of the multiplier 17 is input to the division terminal.
The point is that a divider 18 for inputting the output signal of the coefficient setting unit 16 to the division terminal is provided.

Here, the coefficient setting device 16 is a rated value setting device 2
1 and the buffer 22 for inputting the rated command value IR of the rated value setting device 21, the effective value A output from the effective value detecting circuit 15, and the rated command value IR of the rated value setting device 21 are compared.
An operational amplifier 23 for performing an operation, and an OR circuit 26 including a buffer 22 and diodes 24 and 25 provided at an output of the operational amplifier 23 are provided.

When the effective value A of the effective value detecting circuit 15 is equal to or less than the rated command value IR, the rated command value IR is output to the output of the buffer 22, while the rated command value IR is input to the operational amplifier 23. The output of the operational amplifier 23 becomes zero, and the rated command value IR is output to the output of the coefficient setting unit 16 as shown in FIG. This rated command value IR is
, The compensation target current Ih of the compensation target current detection circuit 11 is divided, and the output signal I
c ′ is Ih / IR. That is, the value is constant during the limiting operation regardless of the magnitude of the effective value A.

Next, when the effective value of the effective value detecting circuit 15 exceeds the rated command value IR, the rated command value IR is output to the output of the buffer 22, while the effective value is output to the output of the operational amplifier 23. A outputs the output signal K of the coefficient setting unit 16
Becomes K = A as shown in FIG. This coefficient setting device 16
Is input to the division terminal of the divider 18, the compensation target current Ih of the compensation target current detection circuit 11 is divided, and the output signal Ic ′ of the divider 18 becomes Ic ′ = Ih / K = Ih / A. Then, a compensation current command signal ic 'is formed.

The compensation current command signal ic 'and the compensation current detection signal detected by the current detector 13 are matched, and the bridge inverter of the current regulator 3 is controlled via the control circuit 14 so that the deviation becomes zero. Are PWM controlled, and the compensation current is controlled.

With this configuration, even if the effective value of the effective value detection circuit exceeds the rated command value with a simple configuration, that is, even if the device is overloaded, no harmonic components not to be compensated are generated. Even in the case of having a value corresponding to an overload of a harmonic component or a reactive power component to be compensated, a continuous operation can be stably performed.

In the present embodiment, the current flowing through the load 2 is detected, but the current flowing through the power supply 1 may be detected by the current detector 10 as shown in FIG. In this case, a compensation target current controller 27 is provided which sets a value subjected to feedback control so as to cancel the harmonic current component extracted by the compensation target current detection circuit 11 as a compensation target current. The current to be compensated by the compensation controller 27 is input to the effective value detection circuit 15 and the division terminal of the divider 18.

Feedback control is performed so as to compensate for and cancel harmonics or a reactive current component of the current flowing through the power supply 1, and an extra harmonic component is generated with a simple configuration even when overloaded, as in FIG. It is compensated stably without doing.

The power supply voltage shown in FIG. 4 is detected by a voltage detector 28, a harmonic voltage component to be compensated is extracted by a compensation voltage detecting circuit 29, and feedback is performed so as to cancel the harmonic voltage component. A current to be compensated is obtained by the compensated current controller 27 for the controlled value. The current to be compensated is input to the effective value detection circuit 15 and the terminal to be divided of the divider 18.

Then, feedback control is performed so that harmonics or an ineffective voltage component of the power supply voltage of the power supply 1 are compensated and canceled, and the generation of an extra harmonic component can be controlled with a simple configuration even when an overload occurs. Can be compensated stably.

In the above embodiment, the compensation target detection circuit 1
The calculated value A is obtained by calculating the effective value of the current 1 to be compensated, but the calculated value A may be provided by calculating the average value and the peak value.

[0028]

According to the first aspect of the present invention, even if the apparatus is overloaded with a simple configuration, it does not generate a harmonic component that is not to be compensated, and the harmonic component to be compensated or Even when the reactive power component has a value corresponding to the overload, the continuous operation can be stably performed.

According to the second aspect of the present invention, with a simple configuration, even if the apparatus is overloaded, the apparatus can be stably compensated without generating extra harmonic components.

According to the third aspect of the present invention, with a simple configuration, even when the apparatus is overloaded, the generation of unnecessary harmonic components can be suppressed, and the apparatus can be stably compensated.

According to the present invention, when the calculated value is equal to or less than the rated command value, the coefficient 1 is output to the output of the coefficient setting unit from the buffer, and the calculated value exceeds the rated command value. When the output of the buffer is input to the operational amplifier and compared with the operation value, the operation value can be output to the output of the coefficient setting device. Based on this, the current regulating device can be controlled. As a result, at the time of an overload for the device, the generation of excess harmonic components can be suppressed, and stable compensation is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a current compensation device according to the present invention.

FIG. 2 is a characteristic diagram of a coefficient setting device in FIG. 1;

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

FIG. 4 is a block diagram showing another embodiment of the current compensator according to the present invention.

FIG. 5 is a block diagram of a conventional current compensator.

FIG. 6 is a diagram showing characteristics of the coefficient setting circuit in FIG. 5;

[Explanation of symbols]

 2 Load 3 Transformer 4 Current Adjuster 7 Reactance Device 10 Current Detector 11 Current Detector for Compensation 13 Current Detector 14 Control Circuit 15 Effective Value Detector 16 Coefficient Setter 18 Divider 21 Rated Value Setter 22 Buffer 23 Calculation Amplifier 24, 25 Diode 26 OR circuit 27 Current controller to be compensated 28 Voltage detector 29 Voltage controller to be compensated 30 Coefficient setting device L Power system

Claims (4)

[Claims] 1. A current regulating device for controlling a compensation current for compensating a harmonic or reactive power component of a power system, a current detector for detecting a load current, and a harmonic or reactive power of the power system from the detection signal. A compensating current detection circuit for extracting a compensating component of the component; a calculating circuit for calculating any one of an effective value, an average value, and a peak value of the compensating component to obtain a calculated value; A coefficient setter for outputting a coefficient 1 when the rated command value is equal to or less than the rated command value, and a coefficient setting device for outputting the calculated value as a coefficient when the rated command value is exceeded, and a compensation current obtained by dividing the component to be compensated for by the coefficient. A current compensator comprising: a divider for calculating a command signal; and a control device for controlling the current regulator so that the compensation current matches the compensation current command signal. 2. A current adjusting device for controlling a compensation current for compensating for a harmonic or a reactive power component of a power system, a current detector for detecting a current output from a power supply, A compensation target current detection circuit that extracts a wave or a reactive power component, a compensation target current controller that is feedback-controlled to cancel the extracted signal, and an effective value, an average value, or an effective value of the compensation target component of the compensation target controller. An arithmetic circuit for calculating one of the peak values to obtain an arithmetic value; a coefficient of 1 when the arithmetic value is equal to or less than a rated command value for instructing a rated value of the device capacity; A coefficient setter that outputs a value as a coefficient, a divider that divides the compensation target component by a coefficient to calculate the compensation current command signal, and a divider that adjusts the compensation current to the compensation current command signal. A current compensator provided with a controller for controlling the current regulator. 3. A current regulating device for controlling a compensation current for compensating for a harmonic or a reactive power component of a power system, a voltage detector for detecting a power supply voltage, and detecting the detection signal with the harmonic or reactive power of the power system. A compensation target voltage detector that extracts a component, a compensation target voltage controller that is feedback-controlled to cancel out the extracted signal, and an effective value, an average value, or a peak value of the compensation target component of the compensation target voltage controller. An arithmetic circuit for calculating any one of them to obtain a calculated value; a coefficient 1 when the calculated value is equal to or less than a rated command value for instructing a rated value of the device capacity; and a calculating coefficient when the calculated value exceeds the rated command value. A coefficient setting device that outputs the compensation current component, the divider that divides the compensation target component by the coefficient to calculate a compensation current command signal, and the current adjustment device so that the compensation current matches the compensation current command signal. A current compensator provided with a controller for controlling the current. 4. A rated command value setting device in which the coefficient setting device commands a rated value of a device capacity; a buffer for amplifying the rated command value; and an operational amplifier for comparing an output of the buffer with the computed value. 4. The current compensator according to claim 1, wherein the current compensator includes an operational amplifier that performs the operation, and an OR circuit provided at an output of the operational amplifier.