JPH03273826A - Active filter used also passively - Google Patents

Abstract

PURPOSE:To prevent an adverse effect on juxtaposed apparatus due to the harmonic voltage at a power receiving point by suppressing respective harmonic voltages at the power receiving point and power supply system due to harmonic components of a load current through using first and second PWM converters. CONSTITUTION:PWM converters 4, 4' conducts suppressing harmonic waves by turning ON-OFF their switching elements by a trigger signal generated in a controller. With regard to fundamental waves, when an AC filter 6 is operated as a phase-advancing capacitor and further the PWM converters 4, 4' are operated as zero impedances, a fundamental wave voltage is no longer applied to the PWM converters 4, 4'. With regard to the harmonic waves also, the PWM converter 4' works so that the AC filter 6 more absorbs the harmonic current of a load 7 and the PWM converter 4 works so that the harmonic voltage of the power supply system is not applied to the receiving point. That is, the harmonic voltage of the receiving point can be reduced to almost zero so that an adverse effect on other juxtaposed apparatus can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of Dou Tojo] The present invention relates to a passive and active filter that compensates for harmonic current.

[Conventional technology]

An AC filter consisting of a tuned filter consisting of a series circuit of a capacitor and an actuator that resonates with a single harmonic, a high-order filter consisting of a parallel circuit of a resistor and reactor, and a series circuit of a capacitor, and a connection between this AC filter and a nonlinear load. 3 in series with the power supply via a transformer on the power supply side from the point
The active filter combined with a phase voltage type PWM converter is well known as explained in the Proceedings of the National Conference of the Industrial Application Division of the Institute of Electrical Engineers of Japan in 1988, paper number 64 "Harmonic suppression device based on a new principle", etc. It is. Also, a power filter is constructed by connecting an AC filter and a three-phase voltage type PWM converter in series with the AC filter via a transformer.

The active filter combined with SIB is as explained in the Proceedings of the 1989 National Conference of the Industrial Application Division of the Institute of Electrical Engineers of Japan, paper number 76, "Harmonic suppression device based on a new principle - Series connection system of LO filter and PWM converter" etc. It is publicly known.

Figure 3 shows a conventional PWM converter connected in series to the power supply.
A system diagram showing an example of a Sanwa AC system equipped with a combined active filter. Figure 4 is its equivalent circuit. Figure 5 is a system diagram when a PWM converter is connected in series with an AC filter. Figure 6 is its equivalent circuit. The equivalent circuit shown in FIG. 7 is a control circuit for a PWM converter.

In Figures 3 and 5, l is a three-phase AC power supply;
2 is the power inductance, 3.3' is the transformer, 4.4'
is a PWM converter, 5.5' is a DC capacitor, 6 is an AC filter, and 7 is a load.

In addition, in FIGS. 4 and 6, j3 is the power supply current,
IL is the load current, 12 is the AC filter 1lllt-Vs
is the supply voltage of the three-phase AC system power supply, VC is the PWM converter output voltage, V〒 is the receiving point voltage, and zr is the impedance of the AC filter.

That is, the three-phase AC system power supply 1 supplies power to a load 7 such as a thyristor Leonard device through a power supply inductance 2. The AC filter 6 includes a fifth harmonic tuning filter consisting of a series circuit of a capacitor 61 and a reactor 62 that resonates with the fifth harmonic, and a seventh harmonic tuning filter consisting of a series circuit of a capacitor 63 and a reactor 64 that resonates with the seventh harmonic.
It is composed of a high-order filter having an effect of absorbing more than the 11th harmonic by connecting a harmonic-tuned filter, a parallel circuit of a resistor 66 and a reactor 67, and a capacitor 65 in series, and absorbs the harmonic current of the load 7. The voltage type PWM converter 4 is connected in series to the power supply via the transformer 3, and the voltage type PWM filter 44' is connected in series to the AC filter 6 via the transformer 3'. On the other hand, it is controlled by a control circuit as shown in Figure 7 so that it has zero impedance and acts as a resistance of several Ω against harmonic voltage. Note that the capacitor 5.5' is for keeping the DC voltage constant.

In FIG. 7, 101 is a power calculation circuit, 102 is a bypass filter, 103 is a two-phase current calculation circuit, and 104 is (
2-phase/3-phase) conversion circuit, 105 is a triangular wave generation circuit, 1
06 is an amplifier, and 107 is a voltage control circuit.

In addition, 1str * isv, isw are the three-phase power supply current, VTTJ-, *, *, * ■A V l "TW is the three-phase power receiving point voltage, IU, 1v,
1w is the current command value of each phase converted from two-phase to three-phase, S
is the triangular wave carrier voltage, and vG is the signal that hits the switching element of the PWM converter.

Then, the power calculation circuit 101 calculates the power supply current 'gelis'.
v, isw and receiving point voltage vTU, vTv# V
tw is input.

Here, instantaneous real power p, imaginary power q, and two-phase current 1sa
cz, ``!111β is calculated as follows.

However, ea, eβ and 15a, 15β are the receiving point voltages VTU and Viv r VTw and ft1l and 15b respectively.
1str - igv * igvwo (two-phase to three-phase) conversion, where p and q are the exchanges of the instantaneous real power p and the instantaneous imaginary power q.

The bypass filter 102 outputs the respective exchanges p and q of the instantaneous real power p and the imaginary power q. The two-phase current calculation circuit 103 calculates the exchange rate p+q of the instantaneous real power p and the imaginary power q, and the receiving point voltage V? U-Vty-V
TW Input Lr formula (2) Two-phase current 1saa
and outputs i and β. The conversion circuit 104 inputs the two-phase current 'fiHa and ismβ, and outputs the current command value j (1, 凰v+iw)'' by (2-phase-3-phase) conversion. iU*, V*,
It inputs i-, multiplies it by the gain, and outputs □ as voltage command signals KIU, x, v. The triangular wave generation circuit 105 outputs a triangular wave carrier voltage S having a frequency of several kHz or more. The voltage control path 107 compares the triangular wave carrier voltage S with the voltage command values KKrJ, KIv and controls the output of the PWM conversion fF4.

The passive and active filter having the PWM converter 4 and the AC filter 6 etc. controlled in this way is such that, in the equal superiority circuit shown in FIG. Harmonic voltages do not appear in the receiving point voltage vT.

Further, the PWM converter 4' is connected in series to the AC filter 6 via the transformer 3'. The PWM converter 4' is similarly controlled by a control circuit as shown in FIG. 7, and as shown in the equivalent circuit of FIG. Harmonic current due to the wave voltage does not flow into the AC filter 6.

[Problem to be solved by the invention]

However, in a passive and active filter that has a PWM converter in series with such a power supply, the harmonic voltage contained in the power supply is suppressed, but if the harmonic current component of the load current is igH, then the voltage at the receiving point is vT is the impedance ZIP of the AC filter and the high frequency component igi of the load current
(Zr'1xT), and harmonic voltage appears at the power receiving point, which adversely affects other equipment installed in parallel.

On the other hand, in a passive combined active filter that has a PWM converter in series with an AC filter.

Harmonic VIIH contained in the power supply appears and similarly has an adverse effect on other equipment attached to the power receiving point.

[Means to solve the problem]

The present invention has been made in view of the above points,
A specific example of the configuration is as follows.

That is, an AC filter connected to the power supply system in parallel with load equipment, a first transformer whose primary side is connected in series to each phase at the other end of the AC filter, and a secondary side of the first transformer. A first PWM converter connected to the first PWM converter, a first DC capacitor connected between the first DC capacitor of the first PWM converter, and a first DC capacitor connected in series to the power supply on the power supply side from the connection point between the load equipment and the AC filter. a second PWM converter connected to the secondary side of the second transformer, and a second PWM converter connected between the DC terminals of the second PWM converter. DC capacitor, and a control device that controls the voltage of the first and second PWM converters, and the control device detects the power supply current of the power supply system and calculates the harmonic current. means for inputting a harmonic current and outputting a second voltage command signal multiplied by the gain; and means for comparing the second voltage command signal and the triangular wave carrier voltage and transmitting the harmonic current to the first and second PWM converters. and means for generating a switch command.

Furthermore, the AC power supply system connected in parallel with the load equipment
an IL filter, a first transformer whose primary side is connected in series to each phase at the other end of the AC filter, a first PWM converter whose primary side is connected to the secondary side of the first transformer, and a first PWM converter connected to the secondary side of the first transformer. Between the DC terminals of PWM converter 1! ! The damaged GL DC capacitor, the 1!2 transformer whose primary side was connected in series with the power supply on the power supply side from the connection point between the load equipment and the AC filter, and the 2nd transformer.
a second PWM converter connected to two dueling transformers of;
A second DC capacitor connected between the DC terminals of the second PWM converter, and a control device that controls the voltage of the first and second PWM converters, and the control device means for detecting the power supply current of the power supply system and calculating the harmonic current, means for inputting the harmonic current and outputting a second voltage command signal multiplied by the gain, and a means for outputting the second voltage command signal and the triangular wave carrier. Compare the voltage to the second PW
means for generating a switch command to the M converter; means for detecting the power receiving point voltage and calculating a harmonic voltage; and means for inputting the harmonic voltage and outputting a first voltage command signal multiplied by the gain; and means for comparing the first voltage command signal and the triangular wave carrier voltage to generate a switch command to the PWM converter of Ml.

[For production]

With this configuration, each soma harmonic current of the power supply system is calculated, each soma ll4aIE current is multiplied by a gain (6), and the first
Second, by making each phase voltage command signal of the first and second PWM converters, each phase voltage command signal of the second PWM converter is made, and the harmonic voltage of the receiving point voltage is By calculating and multiplying each soma harmonic voltage by a gain (6) to obtain each phase voltage command of the first PWM converter, the first PWM converter connected in series to the AC filter Since most of the harmonic current of the load can be absorbed by the output harmonic voltage, the harmonic voltage based on (iFZF) can be suppressed, and the harmonic voltage of the power supply system can be suppressed by the harmonic voltage output by the second PWM converter. It is possible to suppress the voltage from being applied to the power receiving point.

That is, the harmonic voltage at the power receiving point can be reduced to almost zero, and other equipment installed in parallel can be prevented from being adversely affected.

Hereinafter, the present invention will be explained in detail based on embodiment drawings.

[Actual example]

FIG. 1 is a block diagram of main parts showing a first embodiment according to the present invention. In the figure, the same symbols as those shown in FIGS. 3 and 5 indicate the same functions.

In FIG. 1, a transformer 3' is connected to the a end of the AC filter 6.
A PWM converter 4' is connected to its secondary winding, and a DC capacitor 5' is connected between its DC terminals. In addition, the load 7 and the AC filter 6
A second transformer 3 is installed in series with the power supply on the power supply side from the connection point with the power supply.
The primary winding is connected, and the secondary winding of the transformer 3 has P
A WM converter 4 is connected, and a DC capacitor 5 is connected between DC terminals of the PWM converter 4. here,
The DC capacitor 5.5' is for keeping the DC side voltage constant.

In such a circuit connection, the PWM converter 4.4' is connected as a bridge circuit in which diodes are connected in antiparallel to switching elements that can be turned on and off, respectively, and this is generated by a control device as shown in FIG. Tori is signal V
From this, the switching element is turned on and off to perform harmonic suppression.

For the fundamental wave, if the AC filter 6 is operated as a phase advancing capacitor and the PWM converter 54.4' is operated as a zero impedance, the PWM converter 4
．． No fundamental wave voltage is applied to 4'. In addition, for harmonics, the PWM converter 4'
works to absorb the high 11-wave current of the load, and PW
The M converter 4 can be configured to work so that harmonic voltages of the power supply system are not applied to the power receiving point.

FIG. 2 is a block diagram showing a second embodiment according to the present invention.

In FIG. 2, 105' is a triangular wave generation circuit, and 107'
.

114 C voltage control circuit, 108 band pass filter,
109 is a (d-q) conversion circuit, 110 is a bypass filter, 111 is a two-phase voltage calculation circuit, 112 is a (two-phase/three-phase) conversion circuit, and 113 is an amplifier. In the figure, the same reference numerals as in FIG. 7 indicate parts having the same functions.

Then, the bandpass filter 108 has a receiving point voltage vTU
, "TV," 〒W is input, and its basic voltage a is U, vV, VW, IC power calculation circuit M 101 , two-phase 1fifi calculation circuit 103 and conversion circuit 109 . It is output to the two-phase voltage calculation circuit 111.

Here, a power calculation circuit 101, a bypass filter 10
2. Two-phase current calculation circuit 103, conversion circuit! 04. The part consisting of the triangular wave generation circuit 105', the amplifier 106, and the voltage control circuit 107' is the same as the configuration shown in FIG.
It is clear that the voltage of the PWM converter 4 can be controlled.

Further, the conversion circuit 109 has a receiving point voltage vTυ,Va,.

VTW and power supply basic voltage VU, Vv, V,
is input, and the d-axis voltage Vd and the q-wheel load pressure V are output to the bypass filter 9110. The bypass filter 10 outputs the input exchange voltages vd and vq to the two-phase voltage calculation circuit 111.

The two-phase voltage calculation circuit 111 calculates the voltages vU, vy, vy
Input the exchange voltage Vd, V and the two-phase voltage v, ,
V/ is output to the conversion circuit 112.

Here, vsa and vsβ are the receiving point voltages V? IT Iv
TV+V? This is a (two-phase to three-phase) conversion of W.

Then, the conversion circuit 112 inputs the two-phase voltages Va and Vp and converts them (two-phase ° - three-phase) to convert the voltage command value Ma IVy.
, MaW is output. Increase II device! ! 3 inputs voltage command values VU and MAvrvw, multiplies them by the gain, and outputs voltage command values Kvυ, Kvv, KvW.

Therefore, the voltage control circuit 114 controls the triangular wave carrier voltage S'
A trigger signal vG□ is generated by comparing the voltage command values KVU I KVV and KVW, and the PWM converter 4'
The output can be controlled.

〔Effect of the invention〕

As explained above, in the passive combined active filter, the first P
The WM converter suppresses the harmonic voltage at the power receiving point based on the harmonic component of the load iE current, and the second PWM converter connected in series from the power receiving point to the tIjI side suppresses the harmonic voltage in the power supply system. This makes it possible to reduce the high fAIjl voltage at the power receiving point to almost zero, thereby providing an exceptional device that does not adversely affect other equipment attached.

[Brief explanation of drawings]

FIG. 1 is a main part configuration diagram showing a first embodiment according to the present invention,
FIG. 2 is a diagram showing a second embodiment of the present invention. In addition, Figures 3 to 7 are shown to explain the prior art, and Figures 3 and 4 are system diagrams of a combined active filter with a PWM converter connected to the power supply side from the power receiving point. and equivalent circuit, FIG. FIG. 6 is a system diagram and an equivalent circuit in which a PWM converter is connected in series to an AC filter, and FIG. 7 is a diagram of a control circuit. 1...3-phase AC system power supply, 3.3'-...
・Transformer, 4.4'... PWM conversion gain, 5.5
'...-DC capacitor, 6... AC filter, 7... Load, 101...- Power calculation circuit, 102, 110... Bypass filter , 103...Two-phase current calculation circuit, 104
, 109. 112... Conversion circuit, 105, 105' River... Triangular wave generation circuit, 106, 113... Amplification@, 107, 107', 114 River... Voltage control circuit, 108... ...Band pass filter, 11
1...--Two-phase voltage calculation circuit.

Claims (1)

[Claims] 1. An AC filter connected in parallel with load equipment in a power supply system, a first transformer whose primary side is connected in series to the other end of the AC filter, and the first transformer. A first PWM converter connected to the secondary side of the converter, a first capacitor connected between the DC terminals of the first PWM converter, and a power source from the connection point between the load equipment and the AC filter. a second transformer whose primary side is connected in series to the side, a second PWM converter connected to the secondary side of the second transformer, and a DC terminal of the second PWM converter. a second DC capacitor connected between;
A control device that performs voltage control of a first PWM converter and a second PWM converter, and the control device includes:
A means for detecting and calculating a harmonic current included in a power supply current of a power supply system, a means for outputting a second voltage command signal obtained by multiplying the gain of the harmonic current, and a means for generating a triangular wave carrier voltage and for generating the carrier voltage. and the second voltage command signal to control the first PWM converter and the second PWM converter.
1. A combination of passive and active filter, comprising: means for generating a switch command for a converter. 2. An AC filter connected to the power supply system in parallel with the load equipment, a first transformer whose primary side is connected in series to the other end of the AC filter, and an AC filter connected to the secondary side of the first transformer. A connected first PWM converter, a first capacitor connected between the DC terminals of the first PWM converter, and a primary capacitor connected in series to the power supply side from the connection point between the load equipment and the AC filter. a second transformer connected to the secondary side of the second transformer; a second PWM converter connected to the secondary side of the second transformer; and a second PWM converter connected between the DC terminals of the second PWM converter. 2 DC capacitor,
A control device that performs voltage control of a first PWM converter and a second PWM converter, and the control device includes:
means for detecting and calculating a harmonic current included in a power supply current of a power supply system; a means for outputting a second voltage command signal obtained by multiplying the gain of the harmonic current; a means for generating a triangular wave carrier voltage; means for comparing the carrier voltage and the second voltage command signal to generate a second switch command for the second PWM converter; means for detecting and calculating a harmonic voltage included in the power receiving point voltage; means for outputting a first voltage command signal multiplied by the gain of the harmonic voltage; and means for comparing the triangular wave carrier voltage and the first voltage command signal to generate a first switch command for the first PWM converter. A combination of passive and active filters.