JPS62277065A - Active filter device - Google Patents

Abstract

PURPOSE:To reduce the capacity of an active filter by superposing tertiary harmonic wave component on the basic wave component of the filter, superposing the output further on a predetermined harmonic wave voltage, and then controlling the output current of an inverter. CONSTITUTION:A load current is detected by current transformers 8a-8c, the outputs are input through basic wave removing circuits 9a-9c to adders 10a-10c to be added with the outputs of current transformers 6a-6c for detecting the input current of the filter 5. The outputs of the adders 10a-10c are input through amplifiers 11a-11c and adders 12a-12c to a PWM wave forming circuit 13. The adders 12a-12c superpose a voltage having triple frequency synchronized with a power source voltage and a harmonic wave voltage corresponding to a harmonic wave current to be compensated on the outputs of the amplifiers 11a-11c.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to an active filter device composed of a PWM inverter.

[Conventional technology]

Figure 3 shows, for example, ``Outdoor self-cooling voltage type active filter'' of 1985 Electrical and Information Related Societies Federation Conference J (
1 is a circuit diagram showing a conventional active filter device published in April 1985; FIG.

In the same figure, la, lb, and lc are three-phase AC power supplies, 2a,
2b, 2c are reactors, 3a, 3b, 3c, 3d, 3
e, 3f is a transistor switch, 4 is a capacitor, 5
An active filter is composed of transistor switches 3a to 3'' and a capacitor 4, and this active filter 5 is connected to a three-phase AC power source 1a via reactors 2a, 2b, and 2c.

Connected to lb and lc. 6a, 6b, 6c are current transformers for detecting the input current of the active filter 5; 7 is a harmonic current generating load; 8a, 8b, 8c is a current transformer for detecting the current flowing into the harmonic current generating load 7; 9a ,9b,
9c is a fundamental wave removal circuit; 10a, IOb, and 10c are adder circuits; lla, 11b, and llc are amplification rjs circuits that double the gain; 12a, 12b, and 12c are adder circuits;
3 is a PWM waveform creation circuit, which includes current transformers 6a to 6c.
, 8a to 8C1 load 7, fundamental wave removal circuits 9a to 9C1, addition circuits 10a to 10c, 12a, to 12c, increase circuits 11a to 11c, and PWM waveform creation circuit 13 constitute a control circuit. Then, the PWM waveform generating circuit 13 applies 0N10 to the transistor switches 3a to 3f.
The FF command is given.

Next, the operation will be explained.

In order to clarify the contents of the operation, the waveforms shown in FIG. 4 will be used for explanation. FIG. 4(a) shows a three-phase AC power supply 1a.

One phase E1 of lb and Lc is shown. A fundamental wave current (indicated by a broken line) IF as shown in the same figure (b) is applied to the load 7.
Consider a case where a load current ILa, in which a harmonic current I- is superimposed on the current I-, flows. Although only one phase load current ILm is shown in FIG. ILb+ILc
are detected by current transformers 8a, 8b, and 8c, and the detection signals T Lm" + ILb" + IL are input to fundamental wave removal circuits 9a, 9b, and 9c, respectively, and harmonic components IHa"+■Hb.rlHc The fundamental wave removal circuits 9a, 9c, and 9c are configured, for example, by bypass filters, and as shown in FIG. 4 (C1), they cant the fundamental wave component and pass only the harmonic component Ha'' Create it so that

On the other hand, the input current I Ca+l of the active filter 5
Cb+I Cc is detected by current transformers 6a, 6b, 6c. The detection signal 'Cm" + Icb"
I IC and the above-mentioned harmonic component I Ha'' I
l1lb” r Inc is the adder circuit 1, respectively.
0a, 10b, 10c, ΔI B = I Hll", -1C11Δlb =
Io"Icb" (11ΔIC
=1. The following calculation is performed. Adding circuits 10a, 10b.

Output current Δ11 from 10C. ΔI1. ΔIc is multiplied by amplification circuits 11a, llb, and IIC, and is inputted to adder circuits 12a, 12b, and 12c at the next stage, where the next calculation is performed. Here E,,Eb.

EC indicates each phase voltage of the three-phase AC power supplies 1a to 1c.

MA = E, +K ・Δ11 Mb =E> + K ・ΔI b
(21Mc = EC+K - Δ1c The waveform of the output M of the adder circuit 12a is shown in FIG. 4 (dl) as a representative example.

The above outputs M-, Mb, MC are PWM waveform creation circuit 13
is input. Although not shown in FIG. 3, the PWM waveform generating circuit 13 compares the signal with a triangular wave signal as a carrier wave and outputs an 0N10FF command to the transistor switches 3a to 3f. As a result, if ripples due to carrier waves are ignored, the outputs M, , M, of the adder circuits 12a, 12b, 12c,
Output voltage similar to Mc M F l l M F b +
The active filter 5 will generate MFC. Therefore, the current I flowing into the active filter 5. At Icb and Ice are expressed by the following formula.

L = Eb Eyb
(3) t t Here, the L beam indicates the inductance of the axles 2a, 2b, and 2c.

In equation (2), if the gain K is chosen as ■, Δ11°ΔIb
, ΔIc becomes 0, so from (1)2, IHi=r
Ci r sb= [cb (4)f
llc=Icc is established, and the harmonic current II (anl 1
Since 1b and THc are supplied from the active filter 5, the interharmonic currents flowing from the AC type [1a, lb, and 1c] are reduced.

Now, consider the case where the load current ■La+I Lb+I Le is expressed by the following equation.

IL, = I,, sin ut + I old sin n
c+, +LI Lll= I yl 5in
(ωmu + □ π )+ I Hl sin
n(cqt −W) (51I Lc=
I y+ 5in(ω(-□ π)+ I Hl
sin n(ωj −−π) active filter 5
Considering the case where the above harmonic current component is completely compensated for, the following equation holds true.

1,, II=I l(m sin n cqtI
cb” I oh sin n(ωt = −rt)
(61I Cc= Illc Sjn n(c
ut-□π) From the above equations (3) and (6), the output voltages that the active filter 5 should generate are EF-, Evb,
E□ can be expressed by the following formula.

Eys= Ex +nωL-1u+, cos n
wLEF11= Eb +nuL -1111・
cos n(ut −□ π)EFe=Ec +
nraL ・I+++ ・cos n(L, Jt
-□ π) That is, as shown in Figure 4 (dl), the active filter 5 needs to generate a voltage in which a harmonic voltage is superimposed on a fundamental voltage equal to the power supply voltage E1, and its peak voltage is Ep = E I + iωL・INl
(It will be 81.

[Problem that the invention seeks to solve]

Since the conventional active filter device is configured as described above, the voltage output from the active filter 5 is (
8) As shown in the formula, it is necessary to make the harmonic current ncuL・I, II higher than the peak value E of the power supply voltage E, and especially when compensating for high-order harmonics, the value of n As the value increases, the output voltage EFm of the active filter 5
EFb EFC is 3~ compared to the peak value E of the power supply voltage.
It can reach 4 times as much.

Therefore, the charging voltage of the capacitor 4 needs to be 3 to 4 times the peak value E of the power supply voltage, and as a result, the withstand voltage of the transistor switches 33 to 3r needs to be increased accordingly. However, there is a problem in that the capacity of the active filter 5 increases, making it uneconomical.

This invention was made in order to solve the above-mentioned problems, and it is possible to suppress the output voltage of the active filter to a low level, reduce the capacity of the active filter, reduce the cost, and reduce the size of the active filter. The purpose is to obtain a filter device.

Means for Solving Problem C] The active filter device according to the present invention detects harmonic current as a control target in a three-phase power supply system, and adjusts the output current of an inverter according to the detected value of the harmonic current. A control circuit to be controlled includes a power supply voltage detection circuit that detects a power supply voltage, a triple frequency voltage generation circuit that generates a triple frequency voltage synchronized with the power supply voltage, and an arithmetic circuit that superimposes the triple frequency voltage on the power supply voltage. A harmonic voltage corresponding to a harmonic current is added to the output voltage signal of this arithmetic circuit.

[Effect]

The active filter device of the present invention obtains a third harmonic component by a triple frequency voltage generating circuit, superimposes this third harmonic component on the fundamental wave component of the active filter, and converts this output into a harmonic to be further compensated. This is superimposed on a harmonic voltage corresponding to the current, and then the output current of the inverter is controlled.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
FIG. 1 is a circuit diagram showing an embodiment of the present invention. In addition to the control circuit shown in FIG. 3, the control circuit shown in FIG.
d Loop), and a triple frequency voltage generation circuit 15 that generates a triple frequency sine wave voltage E3 in response to a synchronization signal from the power supply voltage synchronization signal generator circuit 14. and an arithmetic circuit 16a that subtracts the triple frequency sine wave voltage E3 from the power supply voltages E, Eb, and E.
, 16b.

16c. In FIG. 1, the same components as those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted.

Next, the operating principle will be explained.

Synchronized with the three-phase AC power supply voltages E, , E, , EC, respectively,
A triple frequency sine wave voltage E3 having the same phase as the zero voltage is generated by the triple frequency voltage generating circuit 15 in response to a synchronizing signal from the power supply voltage synchronizing signal generating circuit 14 in a waveform shown in FIG. 2 (bl). Next, the arithmetic circuits 16a, 16b,
At 16 c, the power supply voltages E, , E, , Ec are 3
When the doubled frequency sine wave voltage E is superimposed, the voltage after superimposition is expressed by the following equation, and the waveform becomes as shown in FIG. 2 (C1).

E, t = E, -E.

Es = Eb El (9) ET
=EC-El However, it is clear from the above equation that the line voltage (for example, E-Es) is the same as before superimposing the triple frequency sine wave voltage E3, for example, El, 1-Es -E-Eb. It is.

In this case, the peak value E,′ of the phase voltage E,E,,Ea
As shown in Figure 2 (dl), Ep'
=E* +nuL ・IH1= Em −El + n
ωL ·I Ml αφ, and the voltage can be lowered by the triple frequency sine wave voltage E3 compared to equation (8).

By superimposing the triple frequency sine wave voltage E on the power supply voltage in this manner, the output voltage of each phase can be reduced (suppressed) without affecting the line-to-line horn voltage of the active filter 5.

The present invention has been made based on the above-mentioned principle, and its operation will be explained below according to an embodiment shown in FIG.

When three-phase load currents IL, , I+ILC flow through load 7, these load currents I Lm+ [Lb* I L
c is detected by the current transformers 3a, 3b, and 13c, and the detection signals ILm'', ■I°+ILC' are input to the fundamental wave removal circuits 9a, 9b, and 9c, respectively, and harmonic components I
. , ′, I□′, ■, and ♂ are output. On the other hand, the input current of the active filter 5 is 1 cm, I. ,.

ICc is detected by current transformers 6a, 6b, 6c. The detection signal is 1cm" + Tcb" + re
The above harmonic components IHa” + Iob” +
The IHs are adder circuits 10a, 10b, and 10c, respectively.
It is added manually. Addition circuits 10a, 10b, 1
Output current from 0c Δ1.2 ΔI1. ΔIc is multiplied by the amplifier circuits 11a, llb, and llc.

Furthermore, the three-phase AC power supply voltages E, , E, , E are each input to the triple frequency voltage generation circuit 15 via the power supply voltage synchronization signal generation circuit 14, and are triple frequency sine wave voltages having the same phase of zero voltage. Output E3.

Next, the triple frequency sine wave voltage E3 is applied to the arithmetic circuits 16a, 1
6b, 16c and superimposed on the power supply voltage E3°E, , EC. ER of arithmetic circuits 16a, 16b, 15c,
E, , E, are further supplied to adder circuits 12a, 12b, 12c, respectively, and added to the outputs from amplifier circuits 11a, llb, llc to obtain outputs M, , Mb, Mc. Outputs M, , M from these adder circuits 12a, 12b, 12c
,.

Mc is input to the PWM waveform generation circuit 13, and compared with a triangular wave signal as a carrier wave, the transistor switches 3a to
Outputs 0N10FF command to 3f. As a result, if ripples due to carrier waves are ignored, adder circuits 12a and 12b
, 12c output M, ,M,.

The active filter 5 generates output voltages F, . . . , F□+FFe, which are similar to MC.

In the above embodiment, an active filter using a voltage source inverter has been described, but an active filter using a current source inverter may also be used and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the active filter device superimposes a voltage having a triple frequency synchronized with the power supply voltage on the fundamental wave component of the output voltage of each phase of the active filter, and further corresponds to the harmonic current to be compensated. Since the configuration is configured to superimpose harmonic voltages, it is possible to reduce the output voltage of each phase without changing the line-to-line output voltage of the active filter, thereby reducing the capacity of the active filter required to produce the same filter effect. This has the effect of making it cheaper.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an active filter device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of operating waveforms showing the active filter device shown in FIG. 1, and FIG. 3 is a circuit diagram showing a conventional active filter. , FIG. 4 is an explanatory diagram of operating waveforms of the active filter device of FIG. 3. 1 is a three-phase AC power supply, 5 is an active filter, 12 is an addition circuit, 13 is a PWM waveform generation circuit, 14 is a power supply voltage synchronization signal generation circuit, 15 is a triple frequency voltage generation circuit, and 16 is an addition circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 3

Claims (1)

[Claims] In an active filter device equipped with a control circuit that detects harmonic current as a control target in a three-phase power supply system and controls the output current of an inverter according to the detected value of the harmonic current, the power supply voltage is applied to the control circuit. It is equipped with a power supply voltage detection circuit for detecting a power supply voltage and a triple frequency voltage generation circuit for generating a triple frequency voltage synchronized with the power supply voltage.
An active device characterized in that a voltage signal on which the output voltage of the double frequency voltage generation circuit is superimposed and the detected harmonic current control signal are added, and the output current of the inverter is controlled by the signal resulting from this addition. filter device.