JPH08140267A - Active filter device - Google Patents

Abstract

PURPOSE: To perform power factor improvement compensation other than the compensation of harmonic currents of reactive current compensation by computing the compensating current, based on the power factor improvement compensating current corresponding to the surplus compensation capacity judged with a compensation capacity judger, and outputting a control command to an inverter. CONSTITUTION: An inverter 6 controls the power from a DC power unit 7, and supplies a power system with a harmonic compensating current through an output transformer 8. A compensation capacity judger 11 compares the detected voltage of the DC power unit 7 with reference voltage and the lowest voltage, and if it is over the reference voltage, this judges that the compensation capacity is 100%, and for the range from the lowest voltage to reference voltage, this judges that the compensation capacity is 0-100%, and further, for the voltage under the lowest voltage, this judges that the compensation capacity is 0%. The judgment result by this compensation capacity judger 11 is inputted into the multiplier 10a of a power factor improvement compensation current control circuit 10 so as to automatically adjust the quantity of compensating current other than the harmonics. Accordingly, the compensation of the harmonic currents is performed preferentially, and besides the power factor can be improved, according to surplus compensation capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active filter device which preferentially compensates harmonics in a power system.

[0002]

2. Description of the Related Art Generally, an active filter device is provided to a power system according to a power load connected to the power system.
Compensation current is supplied. For example, for a power load for general industry, the compensating current is supplied to the power system for the purpose of suppressing the voltage drop of the power system, reducing the flicker voltage, or compensating for the equivalent reverse current.

On the other hand, most active filter devices used in power systems such as power distribution and reception are designed to compensate harmonics generated by a harmonic generation load.

FIG. 7 shows an active filter device for compensating for such harmonics, which is usually constructed by using a voltage type inverter which is a static power converter.

Harmonic generation load 2a connected to the power system
Load current is detected by the load current detector 2 and input to the harmonic current detector 1a of the harmonic compensation current control circuit 1. On the other hand, the harmonic current detector 1a includes an instrument transformer 3
System voltage is input from here, and harmonic generation load 2a
The harmonic component included in the load current of is detected. The harmonic component is input to the adder 1c via the phase inverting circuit 1b. On the other hand, the harmonic compensating current from the compensating current detector 4 is also input to the adder 1c, and the difference between them is calculated.
It is input to d.

The control command from the compensation current control circuit 1d is
It is input to a gate pulse oscillator 5 which gives a gate pulse to a voltage type inverter 6 (hereinafter referred to as an inverter 6). The inverter 6 controls a power supply from a DC power supply device 7 for supplying a compensation current, which is connected to the DC side of the inverter 6, and supplies a harmonic compensation current to a power system via an output transformer 8. Here, the DC power supply device 7 is composed of a capacitor or a battery. Further, 9 is a voltage detector for detecting the voltage of the DC power supply device 7.

[0007] Such an active filter device for harmonic compensation is normally not disconnected from the power system and always compensates for harmonics that fluctuate depending on the load condition. That is, the output of the inverter 6 also increases or decreases as the harmonic current generated by the harmonic generation load increases or decreases.

The rated capacity of the inverter 6 is determined in consideration of the maximum harmonic current amount of the harmonics generated by the harmonic generation load 2A, and when the harmonic generation amount is small, that is, the output of the inverter. When the current is smaller than the rated capacity of itself, the inverter 6 has surplus capacity. Therefore, the inverter 6 can generate a compensating current other than the harmonic by the surplus capacity of the inverter output.

[0009]

However, it is necessary to increase the rated capacity of the inverter 6 in order to simultaneously compensate both the harmonic current compensation and the non-harmonic compensation. That is, unless the rated capacity of the inverter 6 is increased, the inverter 6 will be capacitively charged when the amount of generated harmonics is large.
Will exceed the capacity limit of. In that case, the voltage of the DC power supply 7 on the DC side of the inverter 6 is significantly reduced, and the responsibility of the compensator cannot be fulfilled.

In this way, when the harmonic current compensation and other compensation, such as power factor correction compensation and reactive current compensation, are also responsible, it is necessary to select and use the inverter 6 having a relatively large rating. .

The object of the present invention is to give priority to the compensation of harmonic current, which is the main duty at a determined small capacity inverter rating, and when there is surplus capacity, other than compensation of harmonic current within that range. It is an object of the present invention to provide an active filter device adapted to perform power factor correction compensation and reactive current compensation.

[0012]

According to a first aspect of the present invention, there is provided an active filter device for compensating ability determination for determining a surplus compensating ability of a compensating current that can be generated by an inverter, based on a voltage of a DC power supply device connected to a DC side of the inverter. And a power factor correction compensation current control circuit for calculating a power factor correction compensation current commensurate with the surplus compensation capability determined by this compensation capability determination device,
A compensation current control circuit for calculating a compensation current based on the harmonic compensation current and the power factor correction compensation current and issuing a control command to the inverter is provided.

An active filter device according to a second aspect of the invention replaces the power factor correction compensating current control circuit according to the first aspect of the invention and calculates a reactive current compensating current commensurate with the surplus compensating ability determined by the compensating ability determiner. This is a reactive current compensation current control circuit.

An active filter device according to a third aspect of the present invention is provided when a plurality of inverters are installed, and each of the plurality of inverters is based on the voltage of the DC power supply device connected to the DC side of each of the plurality of inverters. Compensation capability determiner for determining the surplus compensation capability of the compensation current that can be generated by the inverter of
A power factor correction compensation current control circuit that calculates a power factor correction compensation current that is commensurate with the surplus compensation capability determined by this compensation capability determiner, and a compensation current control command based on the harmonic compensation current and the power factor correction compensation current. A compensation current control circuit for calculating and a distributor for distributing the compensation current control command according to the capacity ratio of each inverter and outputting each inverter are provided.

An active filter device according to a fourth aspect of the present invention replaces the power factor correction compensating current control circuit according to the third aspect of the invention and calculates a reactive current compensating current commensurate with the surplus compensating ability determined by the compensation ability determining device. This is a reactive current compensation current control circuit.

[0016]

First, the compensating capacity judging device judges the surplus compensating capacity of the compensating current that can be generated in the inverter, based on the voltage of the DC power supply device connected to the DC side of the inverter. Then, the power factor correction compensation current control circuit calculates a power factor correction compensation current commensurate with the surplus compensation capacity determined by the compensation capacity determiner, while the reactive current compensation current control circuit complies with the surplus compensation capacity. Calculate the reactive current compensation current. Compensation current control circuit, based on harmonic compensation current and power factor correction compensation current, or harmonic compensation current and reactive current compensation current,
Compensation current is calculated and control command is issued to the inverter.

Further, when a plurality of inverters are installed, first, the compensation capacity determining device determines each of the plurality of inverters based on the voltage of the DC power supply device connected to the DC side of each of the plurality of inverters. The surplus compensation capability of the compensation current that can be generated by the inverter is determined. Then, the power factor correction compensation current control circuit calculates the power factor correction compensation current commensurate with the surplus compensation capacity determined by the compensation capacity determiner, while the reactive current compensation current control circuit invalidates the excess compensation capacity commensurate with the surplus compensation capacity. Calculate the current compensation current. The compensation current control circuit calculates the compensation current based on the harmonic compensation current and the power factor correction compensation current, or the harmonic compensation current and the reactive current compensation current, and the distributor
The compensation current control command is distributed according to the capacity ratio of each inverter.

[0018]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing the first embodiment of the present invention.

Harmonic generation load 2a connected to the power system
Load current is detected by the load current detector 2 and input to the harmonic current detector 1a of the harmonic compensation current control circuit 1. On the other hand, the harmonic current detector 1a includes an instrument transformer 3
System voltage is input from here, and harmonic generation load 2a
The harmonic component included in the load current of is detected. The harmonic component is input to the adder 1c via the phase inverting circuit 1b. On the other hand, the harmonic compensating current from the compensating current detector 4 and the power factor improving compensating current from the multiplier 10a of the power factor improving compensating current control circuit 10 are also input to the adder 1c. A value obtained by subtracting the harmonic compensation current from the added value of the harmonic component and the power factor correction compensation current is output from the adder 1c and input to the compensation current control circuit 1d.

The control command from the compensation current control circuit 1d is
It is input to a gate pulse oscillator 5 which gives a gate pulse to a voltage type inverter 6 (hereinafter referred to as an inverter 6). The inverter 6 controls a power supply from a DC power supply device 7 for supplying a compensation current, which is connected to the DC side of the inverter 6, and supplies a harmonic compensation current to a power system via an output transformer 8. The DC power supply device 7 is composed of a capacitor or a battery.

Here, the power factor correction compensation current control circuit 10
Detects the fundamental wave load current obtained by removing the harmonic current from the output of the load current detector 2 by the fundamental wave current detection circuit 10b, and detects the power factor of the load current by the operating power factor detection circuit 10c together with the system voltage. Further, the phase difference detection circuit 10d calculates a power factor difference (phase difference) between the preset target power factor and the load current power factor, and the phase shift circuit 10e shifts the phase by the power factor difference (phase difference). The calculated current is calculated. And
A vector difference current obtained by subtracting the fundamental wave load current from the phase shift shift current is obtained by the adder 10f, and the compensation capacity determination unit 1
The compensation coefficient from 1 is multiplied by the multiplier 10a. This current becomes the power factor correction compensation current.

Next, the voltage detection value of the voltage detector 6 which detects the voltage of the DC power supply device 7 is input to the compensation capacity judging device 11. The compensating capacity judging device 11 judges the surplus compensating capacity of the compensating current which the inverter 6 can generate based on the voltage of the DC power supply 7.

FIG. 2 is a characteristic diagram showing the relationship of the compensation capability with respect to the voltage of the DC power supply device 7 in the compensation capability determination unit 11.

The DC power supply 7 of the inverter 6 is consumed by the output current (compensation current) of the inverter 6, that is, the amount of inverter loss. If the consumed amount is larger than the charged amount of the DC power supply device 7, the voltage drops with the passage of time. Therefore, in the present invention, the voltage of the DC power supply device 7 is detected and compared with the reference voltage and the minimum voltage, and the comparison result is judged as the surplus capacity of the inverter.

Regarding the voltage of the DC power supply device 7 of the inverter 6, the reference voltage and the minimum voltage are set as follows. That is, the reference voltage is a value several volts below the rated voltage or rated voltage of itself, and
The minimum voltage is a voltage value obtained by subtracting 10 to 15% or less from the rated voltage of itself. As a result, it is possible to maintain the voltage of the DC power supply device 7 within the voltage range from the reference voltage to the minimum voltage, and to compensate the harmonic current and other compensations.

The compensation capacity judging device 11 compares the detected voltage of the DC power supply device 7 with the reference voltage and the minimum voltage, and if the voltage exceeds the reference voltage, the compensation capacity is set to 100% and the range from the minimum voltage to the reference voltage. The compensation capacity is 0 to 100%,
Further, a voltage equal to or lower than the minimum voltage is determined to have a compensation capacity of 0%.

The result of judgment by the compensating capacity judging device 11 is inputted as a compensation coefficient to the multiplier 10a of the power factor correction compensating current control circuit 10 to automatically adjust the amount of compensating current other than harmonics. That is, if the detected voltage of the DC power supply device 7 has reached the reference value, the compensation capability is 100%, and compensation other than harmonics is maximally performed. %, The reduced current is compensated, and when the voltage is lower than the minimum voltage, control is performed without compensation other than the harmonic current.

Therefore, the inverter 6 controls the injection of a current (harmonic compensating current) whose phase is reversed by 180 degrees for compensating the harmonics generated by the harmonic generating load 2a into the power system via the output transformer 8. Will be given priority.

FIG. 3 is a vector diagram showing the relationship between the fundamental wave load current if, the current if 'phase-shifted according to the target power factor (target), and the target power factor improvement compensating current ic.

As described above, when compensating for the power factor improvement other than the harmonic compensation, the presence or absence of the compensation capability of the inverter 6 is
The compensation capacity determiner 11 compares the DC voltage signal output from the voltage detector 9 for detecting the voltage of the DC power supply device 7 of the inverter 6 with the reference voltage and the minimum voltage to make a determination.

In the power factor correction compensation current control circuit 10, the target power factor correction compensation current ic obtained from the target power factor and the output of the compensation judgment unit 11, that is, the compensation coefficient 0 to 100% are multiplied by the multiplier 1.
It is calculated at 0a. This signal is further added to the harmonic compensation current by the harmonic compensation current control circuit 1 by the adder 1c and input to the compensation current control circuit 1d as a compensation current.

As described above, in the first embodiment, the harmonic current compensation is always prioritized, and the power factor can be improved according to the surplus compensation capability. As a result, it is possible to fulfill the compensation duty regarding the harmonic compensation and to improve the power factor with the surplus capacity.

FIG. 4 is a block diagram showing a second embodiment of the present invention. In the second embodiment, a reactive current compensation current control circuit 12 is provided instead of the power factor correction compensation current control circuit 10 of the first embodiment.

Harmonic generation load 2a connected to the power system
Load current is detected by the load current detector 2 and input to the harmonic current detector 1a of the harmonic compensation current control circuit 1. On the other hand, the harmonic current detector 1a includes an instrument transformer 3
System voltage is input from here, and harmonic generation load 2a
The harmonic component included in the load current of is detected. The harmonic component is input to the adder 1c via the phase inverting circuit 1b. On the other hand, the harmonic compensation current from the compensation current detector 4 and the reactive current compensation current from the reactive current compensation current control circuit 12 are also input to the adder 1c. From the adder 1c,
A value obtained by subtracting the harmonic compensation current from the addition value of the harmonic component and the reactive current compensation current is output, and the compensation current control circuit 1d is output.
Is input to

The control command from the compensation current control circuit 1d is
It is input to a gate pulse oscillator 5 which gives a gate pulse to a voltage type inverter 6 (hereinafter referred to as an inverter 6). The inverter 6 controls a power supply from a DC power supply device 7 for supplying a compensation current, which is connected to the DC side of the inverter 6, and supplies a harmonic compensation current to a power system via an output transformer 8. Here, the DC power supply device 7 is composed of a capacitor or a battery.

Here, the reactive current compensation current control circuit 12
Has a multiplier 12a for multiplying a preset target reactive current compensation current irrespective of the load current by a compensation coefficient from the compensation capacity determiner 11, and the current obtained by the multiplier 12a is a reactive current compensation current. Becomes

FIG. 5 is a current vector diagram showing the relationship between the reactive current compensation current id and the load current if of the second embodiment. In the first embodiment, the power factor correction compensation current control circuit 10
In the second embodiment, the reactive current compensation current control circuit 12 converts the power factor correction compensation current ic in FIG. 3 into the load current if. It is irrelevant and is controlled only by the preset reactive current compensation current id.

As described above, in the second embodiment, the harmonic current is always prioritized and compensated, and the constant reactive current can be compensated according to the surplus capacity. As a result, it becomes possible to fulfill the compensation duty regarding the harmonic compensation and compensate the reactive current with the surplus capacity.

Next, FIG. 6 shows a third embodiment of the present invention. In the third embodiment, when the compensation current increases due to an increase in the harmonic generation load 2a or the like, and the capacity of one inverter that has been conventionally used becomes insufficient, the capacity is compensated for. , The case where the inverter 6A is additionally installed.

The harmonic compensating current control circuit 1 and the power factor correction compensating current control circuit 10 or the reactive current compensating current control circuit 12 are shared by a plurality of inverters 6 and 6A. The compensating current command from the compensating current control circuit 1d is distributed by the distributor 13 according to the procedure of the inverter. That is, the distributor 13 distributes the compensating current command corresponding to each inverter capacity ratio to the gate pulse generator 5 that operates the conventionally used inverter 6 and the gate pulse oscillator 5A that operates the added inverter 6A. To do. This allows a plurality of inverters 6 and 6A to be controlled by the common harmonic compensation current control circuit 1. That is, it becomes possible to control a plurality of inverters with one harmonic preferential compensation current control circuit.

[0041]

As described above, according to the present invention, the surplus capacity for compensation other than the harmonic current is judged based on the voltage level of the DC power supply device of the inverter for compensating the harmonic current, and the voltage level is If it is high, compensation other than harmonics, that is, power factor correction compensation and reactive current compensation, is performed, so that harmonic current compensation, which is the original responsibility, can be performed and the inverter can be effectively used.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship of the compensation capability with respect to the voltage of the DC power supply device in the compensation capability determination device of the present invention.

FIG. 3 is an explanatory diagram of a power factor correction compensation current according to the present invention.

FIG. 4 is a configuration diagram showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a reactive current compensation current according to the present invention.

FIG. 6 is a configuration diagram showing a third embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional example.

[Explanation of symbols]

 1 harmonic compensation current control circuit 1d compensation current control circuit 2 load current detector 2a harmonic generation load 3 instrument transformer 4 compensation current detector 5 gate pulse transmitter 6 inverter 7 DC power supply device 8 output transformer 9 voltage detector 10 Power Factor Improvement Compensation Current Control Circuit 11 Compensation Ability Judgment Device 12 Reactive Current Compensation Current Control Circuit 13 Distributor

Claims (4)

[Claims] 1. An inverter for generating a harmonic compensating current for compensating a harmonic generated from a harmonic generating load connected to a power system, and a compensation current supply connected to a direct current side of the inverter. In an active filter device comprising a DC power supply device and a harmonic compensation current control circuit for controlling the inverter so that a harmonic compensation current for canceling the harmonics of the harmonic generation load is supplied to the power system, A compensation capacity determiner that determines the excess compensation capacity of the compensation current that can be generated by the inverter based on the voltage of the DC power supply device, and a power factor correction compensation current that is commensurate with the excess compensation capacity determined by the compensation capacity determiner. A power factor correction compensation current control circuit for calculating, a compensation current is calculated based on the harmonic compensation current and the power factor correction compensation current, and a control command is issued to the inverter. And a compensation current control circuit. 2. The reactive current compensating current control for calculating the reactive current compensating current commensurate with the surplus compensating ability judged by the compensating ability judging device in place of the power factor correction compensating current control circuit according to claim 1. An active filter device comprising a circuit. 3. A plurality of inverters for generating a harmonic compensation current for compensating harmonics generated from a harmonic generation load connected to a power system, and a DC side of each of the plurality of inverters. A DC power supply device for supplying the compensation current, and a harmonic compensation current control circuit for controlling the inverter so that a harmonic compensation current for canceling the harmonics of the harmonic generation load is supplied to the power system. In the active filter device including, a compensation capacity determination device that determines the excess compensation capacity of the compensation current that can be generated by each of the plurality of inverters based on the voltage of the DC power supply device, and the compensation capacity determination device is determined. Power factor correction compensation current control circuit for calculating a power factor correction compensation current commensurate with the surplus compensation capability, and a compensation current based on the harmonic compensation current and the power factor correction compensation current. An active filter device comprising: a compensation current control circuit for calculating a control command; and a distributor for distributing the compensation current control command according to a capacity ratio of each of the inverters and outputting the inverter. 4. The reactive current compensating current control for calculating the reactive current compensating current commensurate with the surplus compensating ability determined by the compensating ability determiner, in place of the power factor correction compensating current control circuit according to claim 3. An active filter device comprising a circuit.