JP2000253577A - Control method for active filter for power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method for an active filter, whereby even if there are a plurality of higher harmonic current sources as loads in a power system, the higher harmonic currents flowing out to the power system are suppressed by a single active filter for power. SOLUTION: A current command value for an active filter is generated through a current command value calculating circuit, comprising a higher harmonic component extracting circuit 31, a function circuit 32, an adder 33, a filter 34, and an inversion amplifier 35. At this time, a current ILH of a plurality of higher harmonic current sources is obtained through estimation from a higher harmonic current ISH flowing out to the power system, extracted through the higher harmonic component extracting circuit 31, through the function circuit 32. The value obtained is taken as the controlled variable of the active filter, and thereby ILH is canceled out by an output current IC of the active filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a power active filter which is connected in parallel with a load as a harmonic current generating source for generating a harmonic current in a power system and compensates the harmonic current. About.

[0002]

2. Description of the Related Art With the spread of semiconductor power converters such as inverters in recent years, harmonic currents generated by these devices have been increasing, and various obstacles caused by the harmonic currents have become a problem. ing. An LC filter or an active power filter (hereinafter, also simply referred to as an active filter) is installed as a device for suppressing the flow of the harmonic current into the power system. The method of applying the active filter is as follows. It is roughly divided into two.

[0003] An individual compensation method for a single harmonic current source, which suppresses a harmonic current of the harmonic current source from flowing out to a power system. . A collective compensation method for a plurality or an unspecified number of harmonic current sources, which suppresses a harmonic current of the harmonic current sources from flowing out to a power system. FIG. 7 is a circuit diagram showing a conventional example of a power active filter applied to the individual compensation method described above.

In FIG. 7, 1 is a power system, 2 is a harmonic current source as a load of the power system 1, 3 is a current detector, 10 is an active filter, and 13 is a current command value for the active filter 10. Is a current command value calculation circuit. As shown in FIG.
An active power conversion circuit formed by a three-phase bridge connection of an antiparallel circuit of a GBT and a diode, a capacitor connected to the DC side of the power conversion circuit, and a reactor connected to the AC side of the circuit. A conversion formed by a filter main circuit 11, a current control loop for outputting each phase current based on the current command value from the current command value calculation circuit 13 from the active filter main circuit 11, a PWM calculation circuit, a gate drive circuit, and the like. And a controller control circuit 12.

The current command value calculation circuit 13 extracts a harmonic current component of each phase from the detected value of the current detector 3 by a known technique, and calculates an opposite phase value of the extracted harmonic current component of each phase. It is sent to the converter control circuit 12 as a current command value. FIG. 8 is an equivalent circuit diagram for the harmonic current in the circuit configuration shown in FIG. 7, in which the impedance of the power system 1 is Z _S , the harmonic current of the harmonic current source 2 is I _LH , When the output current is I _C, active filter 10 operates such that I _C = -I _LH, resulting, active filter 10 acts equivalently as a current source.

FIG. 9 is a circuit diagram showing a conventional example of an active power filter applied to the above-described collective compensation method. In FIG. 9, reference numeral 1a denotes an upper power system, 1b denotes a lower power system, 2a and 2b denote harmonic current sources as loads of the lower power system 1b, and 4 denotes an upper power system 1a and a lower power system 1b. 5 is a current detector, 6 is a load of the lower power system 1b, 7 is an LC filter for suppressing harmonic current of the lower power system 1b, 1
Reference numeral 0 denotes an active filter having the same configuration as the circuit shown in FIG. 7, and reference numeral 20 denotes a current command value calculation circuit that generates a current command value for the active filter 10.

The current command value calculation circuit 20 extracts a harmonic current component of each phase from the detection value of the current detector 5 which collectively detects the current of the lower power system 1b by a known technique. Multiply the harmonic current component by gain (K),
The value of the opposite phase of the K times value is set as the current command value of each phase as shown in FIG.
Is transmitted to the converter control circuit 12 shown in FIG. FIG.
9 shows an equivalent circuit diagram for harmonic current in the circuit configuration shown in FIG. 9, wherein the impedance on the power system side viewed from the lower power system 1b is Z _S , and the lower power system 1b
The impedance of the load side viewed from the Z _F, the harmonic current flowing out to a lower power system 1b and I _SH, harmonic current source 2a, the harmonic currents 2b and I _LH, the output of the active filter 10 Assuming that the current is I _C and the harmonic voltage of the lower power system 1b is V _H , the active filter 10 operates so that I _C = −K · I _SH .

At this time, since I _SH = V _H / Z _S , I _C can be modified as shown in the following equation (1).

[0009]

I _C = −K · I _SH = −V _H / (Z _S / K) (1) Therefore, the active filter 10 acts equivalently as an impedance of Z _S / K. That is, the harmonic current I _LH is shunted to I _SH and I _C. If the value of K is made sufficiently large, I _SH ≪I _C and the lower power system 1
The harmonic current to b can be suppressed.

[0010]

In the conventional circuit configuration shown in FIG. 9, the active filter 10 is used as described above.
Acts equivalently as a low-impedance source, but it is common for a specific resonance frequency to exist between this equivalent impedance and the other impedances in the power system. In some cases, the harmonic current is increased by the active filter 10 in the vicinity of the frequency at which the harmonic current is caused (this state is called “harmonic current increase phenomenon due to anti-resonance”).

In order to prevent the above phenomenon, the individual compensation method described above may be applied. In this method, a plurality of active filters are provided for a plurality of harmonic current sources. There was a problem that the price became high as a whole. An object of the present invention is to provide a control method for an active power filter that solves the above-mentioned problems.

[0012]

The first invention is connected in parallel with a load as a harmonic current generating source for generating a harmonic current I _SH for a power system, and compensates for the harmonic current. in an active filter power, the detected value of the harmonic current, said derived from the ratio of the current I _LH and the I _SH harmonic current source (I _SH / I _LH) in based transfer function G _(s) Calculate the difference between the calculated value and the detected value of the output current of the active filter, and calculate the difference between the calculated value and the output current command value to the active filter. Control method.

[0013] The second invention is an active filter for power, the detected value of the harmonic current, based on the ratio of the current I _LH of the harmonic current source and said _{I SH (I SH / I LH} ) A value through an inverse system derived from the transfer function G _(s) is calculated, and a difference between the calculated value and an output current command value to the active filter is obtained. Use a control method that sets a new output current command value to the active filter.

A third invention is in the active filter power, the detected value of the harmonic current, based on the ratio of the current I _LH of the harmonic current source and said _{I SH (I SH / I LH} ) Calculate a value through an inverse system derived from a transfer function G _(s) , obtain a difference between the calculated value and a detected value of the output current of the active filter, and determine the difference and the detection of the harmonic current. A value is obtained by adding a value obtained by multiplying the value by a gain (K), and a control method is used in which a value having a phase opposite to the added value is set as an output current command value to the active filter.

[0015] A fourth aspect of the invention is in the active filter power, the detected value of the harmonic current, based on the ratio of the current I _LH of the harmonic current source and said _{I SH (I SH / I LH} ) Calculate a value through an inverse system derived from the transfer function G _(s) , obtain a difference between the calculated value and an output current command value to the active filter, and detect the difference and the harmonic current. A value is obtained by adding a value obtained by multiplying the value by a gain (K), and a control method is adopted in which a value having a phase opposite to the added value is set as a new output current command value to the active filter.

According to a fifth aspect of the present invention, in the power active filter control method according to the first to fourth aspects, the inverse system is a function based on the [1 / G _(s) ]. According to the present invention, the transfer function G ₍ based on the ratio (I _SH / I _LH ) between the current I _LH of the harmonic current source and the I _SH with respect to the detected value of the harmonic current flowing into the power system. _s) through the inverse system as the control amount of the power active filter, the current in phase opposite to the sum of the harmonic currents from multiple or unspecified multiple harmonic current sources is calculated. The same operation as the individual compensation method described above, which is output by the active filter, can be performed by one power active filter.

Further, in the third or fourth aspect of the present invention, it is possible to further reduce the harmonic current flowing out to the electric power system while preventing the above-described “harmonic current increase phenomenon due to anti-resonance” by the inverse system.

[0018]

FIG. 1 is a circuit diagram showing a first embodiment of a method for controlling a power active filter according to the present invention, which has the same functions as those of the conventional circuit shown in FIG. Are denoted by the same reference numerals, and description thereof is omitted here. That is, in the circuit configuration diagram shown in FIG.
A current command value calculation circuit 30 or a current command value calculation circuit 40 for generating a current command value for the active filter 10 based on the detection value of the current detector 5 and the detection value of the current detector 14
It has.

FIG. 2 is a detailed circuit configuration diagram of a current command value calculation circuit 30 showing a first embodiment of the control method of the power active filter of the present invention. In FIG. 2, reference numeral 31 denotes a harmonic current component extraction circuit that extracts a harmonic current component of each phase from a detection value of the current detector 5 that collectively detects a current of the lower power system 1b by a known technique, and 32 denotes a harmonic current component extraction circuit. A function circuit including a function described later, 33 is an addition calculator for calculating a difference between an output value of the function circuit 32 and a detection value of the current detector 14 for detecting an output current of the active filter 10, and 34 is an output of the active filter A filter for limiting the frequency band of the current to be applied, and 35 denotes an inverting amplifier.

The harmonic current generator 2a shown in FIG.
The current I of the sum of the harmonic current sources 2b _LHAnd harmonic current components
Outflow to lower power system 1b extracted by extraction circuit 31
Harmonic current I_SHCurrent transfer function G based on_(s)
Is represented by the following equation (2).

[0021]

G _(s) = I _SH / I _LH (2) The transfer function G _(s) represented by the above equation (2) is determined by the impedance of the power system and the load.
From the equivalent circuit shown in FIG. 10 described above, the following equation (3) can be expressed.

[0022]

G _(s) = Z _F / (Z _S + Z _F ) (3) In the function circuit 32, the inverse system derived from the harmonic current transfer function G _(s) expressed by the above equation (3) is used. A function represented by the following equation (4) is obtained in advance as a function.

[0023]

1 / G _(s) = (Z _S + Z _F ) / Z _F (4) Accordingly, the output of the function circuit 32 is transmitted to the lower power system 1b extracted by the harmonic current component extraction circuit 31. The value I _LH is estimated from the outgoing harmonic current I _SH . In general, the function represented by the equation (4) is a higher-order equation, but in practice, both the numerator and the denominator may be approximated by second- and third-order equations.

That is, in the current command value calculation circuit 30 shown in FIG. 2, the difference between the output value of the above-described function circuit 32 and the detection value of the current detector 14 is obtained by the addition calculator 33, and the difference is filtered by the filter 34. And the inverting amplifier 35 are used as current command values for each phase to the active filter 10, so that the harmonic current generation source 2a and the harmonic current generation source 2b
The sum of the current I _LH of the current I _C which active filter 10 outputs the offset, harmonic current is reduced which flows to the lower power system 1b.

FIG. 3 is a detailed circuit configuration diagram of a current command value calculation circuit 40 showing a second embodiment of the control method of the active power filter according to the present invention, and has the same functions as those of the embodiment circuit shown in FIG. Are given the same reference numerals.
That is, in addition to the harmonic current component extraction circuit 31, the function circuit 32, the addition calculator 33, the filter 34, and the inverting amplifier 35, the current command value calculation circuit 40 shown in FIG.
, A multiplication operation unit 41 and an addition operation unit 42.

In the current command value calculation circuit 40, the lower power system 1b extracted by the harmonic current component extraction circuit 31
The value obtained by multiplying the gain (K) of the harmonic current I _SH flowing to the filter 34 is added to the output value of the filter 34, and the value of the phase opposite to the added value is used as the current command value of each phase to the active filter 10. The error associated with the estimation of the I _LH output from the function circuit 31 is compensated for, and the above-mentioned “anti-resonance due to the anti-resonance is obtained by the inverse system function derived from the harmonic current transfer function G _(s) in the function circuit 31. Harmonic current increase phenomenon "
Harmonic current flowing to the lower power system 1b can be suppressed.

FIG. 4 is a circuit diagram showing a second embodiment of the control method of the power active filter according to the present invention. The components having the same functions as those of the conventional circuit shown in FIG. , And the description is omitted here.
That is, the circuit configuration diagram shown in FIG. 4 includes a current command value calculation circuit 50 or a current command value calculation circuit 60 that generates a current command value for the active filter 10 based on the detection value of the current detector 5.

FIG. 5 is a detailed circuit configuration diagram of a current command value calculation circuit 50 showing a third embodiment of the control method of the power active filter according to the present invention, and has the same functions as those of the embodiment circuit shown in FIG. Are given the same reference numerals.
That is, the current command value calculation circuit 50 shown in FIG.
4. In addition to the inverting amplifier 35, an adder 51 is provided.

In the current command value calculation circuit 50, a difference between the output value of the above-described function circuit 32 and the output value of the inverting amplifier 35, that is, the current command value (≒ I _C ) is obtained by the addition calculator 51. By using the value passed through the filter 34 and the inverting amplifier 35 as a new current command value for each phase to the active filter 10, the current I _LH of the sum of the harmonic current sources 2a and 2b And the current I _C output by the active filter 10 are canceled, and the harmonic current flowing out to the lower power system 1b is reduced.

FIG. 6 is a detailed circuit configuration diagram of a current command value calculation circuit 60 showing a fourth embodiment of the control method of the active power filter according to the present invention, and is a circuit diagram of the embodiment shown in FIGS. Those having the same functions as those described above are denoted by the same reference numerals. That is, the current command value calculation circuit 60 shown in FIG.
Includes a harmonic current component extraction circuit 31, a function circuit 32, a filter 34, an inverting amplifier 35, and an addition operation unit 51, as well as a multiplication operation unit 61 and an addition operation unit 62 for the multiplication value K.

In the current command value calculation circuit 60, the lower power system 1b extracted by the harmonic current component extraction circuit 31
The value obtained by multiplying the gain (K) of the harmonic current I _SH flowing to the filter 34 is added to the output value of the filter 34, and the value of the phase opposite to the added value is used as the current command value of each phase to the active filter 10. , supplemented the error associated with the estimation of the I _LH which function circuit 31 outputs, and, by inverse system function derived from the harmonic current transfer function G _(s) of the function circuit 31 by the foregoing "antiresonant Harmonic current increase phenomenon "
Harmonic current flowing to the lower power system 1b can be suppressed.

[0032]

According to the power active filter control method of the present invention, as described above, the value passed through the inverse system is used as the control amount of the power active filter, so that a plurality or unspecified number of harmonics can be obtained. The same operation as in the individual compensation method described above, in which the active filter outputs a current having a phase opposite to the sum of the harmonic currents from the current generation sources, can be performed by one power active filter. Furthermore, the above-mentioned inverse system can further reduce the harmonic current flowing out to the power system while preventing the “harmonic current increase phenomenon due to anti-resonance”.

[Brief description of the drawings]

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

FIG. 2 is a partial detailed circuit configuration diagram of FIG. 1 showing a first embodiment of the present invention;

FIG. 3 is a partially detailed circuit configuration diagram of FIG. 1 showing a second embodiment of the present invention;

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

FIG. 5 is a partial detailed circuit configuration diagram of FIG. 4 showing a third embodiment of the present invention;

FIG. 6 is a partial detailed circuit configuration diagram of FIG. 4 showing a fourth embodiment of the present invention;

FIG. 7 is a circuit configuration diagram showing a conventional example.

FIG. 8 is an equivalent circuit diagram of FIG. 7;

FIG. 9 is a circuit diagram showing a conventional example.

FIG. 10 is an equivalent circuit diagram of FIG. 9;

[Explanation of symbols]

1, 1a, 1b: electric power system, 2, 2a, 2b: harmonic current source, 3: current detector, 4: transformer, 5: current detector, 6: load, 7: LC filter, 10: active Filters, 11: active filter main circuit, 12: converter control circuit, 13: current command value calculation circuit, 14: current detector, 20, 30: current command value calculation circuit, 31: harmonic component extraction circuit, 32 ... Function circuit, 33 addition arithmetic unit, 3
4 Filter, 35 Inverting amplifier, 40 Current command value calculation circuit, 41 Multiplication calculator, 42 Addition calculator, 50
Current command value calculation circuit, 51: addition calculation device, 60: current command value calculation circuit, 61: multiplication calculation device, 62: addition calculation device.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G066 EA03 5H740 BA11 BB09 NN03 5J098 AA02 AA11 AA14 AA16 AB02 AB25 AD21 AD25 CA06 CB03

Claims (5)

[Claims] 1. A power supply system, wherein the power supply is connected in parallel with a load as a harmonic current source for generating a harmonic current I _SH ,
In the power active filter for compensating for the harmonic current, a transfer function based on a ratio (I _SH / I _LH ) between the current I _LH of the harmonic current source and the I _SH is _added to the detected value of the harmonic current. Calculating a value through an inverse system derived from G _(s), and calculating a difference between the calculated value and a detection value of an output current of the active filter. A method for controlling a power active filter, wherein an output current command value is supplied to the power active filter. 2. An active power filter connected in parallel with a load as a harmonic current generating source for generating a harmonic current to a power system and compensating for the harmonic current, wherein the detected value of the harmonic current is Then, a value via an inverse system derived from a transfer function G _(s) based on the ratio (I _SH / I _LH ) of the current I _LH of the harmonic current source to the I _SH is calculated. And a difference between the output current command value to the active filter and the output current command value to the active filter, and a value having the opposite phase to the difference is set as a new output current command value to the active filter. Control method. 3. A power active filter connected in parallel with a load as a harmonic current generating source for generating a harmonic current to a power system and compensating for the harmonic current, wherein the detected value of the harmonic current is Then, a value via an inverse system derived from a transfer function G _(s) based on the ratio (I _SH / I _LH ) of the current I _LH of the harmonic current source to the I _SH is calculated. And a difference between the detected value of the output current of the active filter and a value obtained by multiplying the difference by a gain (K) of the detected value of the harmonic current. A method for controlling a power active filter, wherein a value of an opposite phase is set as an output current command value to the active filter. 4. An active power filter connected in parallel with a load as a harmonic current generating source for generating a harmonic current to an electric power system and compensating for the harmonic current, wherein the detected value of the harmonic current is Then, a value via an inverse system derived from a transfer function G _(s) based on the ratio (I _SH / I _LH ) of the current I _LH of the harmonic current source to the I _SH is calculated. And a difference between the output current command value to the active filter and a value obtained by multiplying the difference by a gain (K) of the detected value of the harmonic current. A method for controlling a power active filter, wherein a value of an opposite phase is used as a new output current command value to the active filter. 5. The control method for an active power filter according to claim 1, wherein the inverse system is a function based on the [1 / G _(s) ]. To control the active power filter.