JPH05284652A - Control circuit for universal filter - Google Patents

Abstract

PURPOSE:To obtain a voltage command containing no basic wave component by subtracting two phase current commands for R and S components, obtained from reverse phase real power R and imaginary power S, from two phase current commands for P and Q components obtained from instantaneous real power P and imaginary power Q of a conventional system. CONSTITUTION:A P, Q operating circuits 101, a high pass filter 102, and a Q component current command value operating circuit 111 deliver Q component two phase current command signals Ialpha, Ibeta to a three-phase command value operating circuit 110. An R, S operating circuit 107, a low-pass filter 108, and an R, S component current command value operating circuit 109 deliver P, Q component two phase current commands Id, Iq to the three-phase command value operating circuit 110. The three-phase command value operating circuit 110 operates each phase compensation current command signal Icu, Icv, Icw which is then fed to an amplifying circuit 104. The amplifying circuit 104 produces voltage command signals Vu, Vv, Vw to a voltage control circuit 106. The voltage control circuit 106 receives a triangular carrier voltage from a triangular wave generating circuit 105 and produces a trigger signal VG for a switching element in a PWM converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive filter in which a reactor and a capacitor connected in parallel to a load in a power supply system are connected in series, and a passive combined active system in which a power converter composed of a switching element is connected in series. The present invention relates to improvement of a filter control circuit.

[0002]

2. Description of the Related Art A passive combined active filter in which a passive filter composed of a series circuit of a reactor and a capacitor and a power converter composed of a switching element are connected in series is described in "AC filter and pulse width modulation type power converter in series". It is known as described in "Connected Harmonic Suppression Device" and the like.

FIG. 2 is a block diagram of the main circuit of a passive combined active filter, and FIG. 3 is a block diagram of its control circuit.

In FIG. 2, an LC filter 3 is connected in parallel to the load in a line in which electric power is supplied from a three-phase AC system power source 1 to a load 2 such as a thyristor Leonard device.
The LC filter 3 includes a capacitor 31 and a reactor 32.
5th harmonic tuning filter consisting of a series circuit of, a seventh harmonic tuning filter consisting of a series circuit of a capacitor 33 and a reactor 34, a higher order consisting of a series circuit of a parallel circuit of a resistor 35 and a reactor 36, and a capacitor 37. It consists of filters. The three-phase power supply currents I _SU , I _SV , and I _SW are configured by combining load currents I _LU , I _LV , and _{IL W} and filter currents I _FU , I _FV , and I _FW , respectively.

The other end of each phase of the LC filter 3 is (Y-Y)
The transformer 7 is connected to the primary side, the other end of the primary side of the transformer 7 is star-connected, and one end of the secondary side is also star-connected, and the other end is an AC reactor 4 for each phase. Are connected in series, and a capacitor 8 is connected to each phase connection point between the secondary side of the transformer 7 and the AC reactor 4.

PWM is provided on the side opposite to the transformer of the AC reactor 4.
A converter 5 is connected, a DC capacitor 6 is connected to the DC side terminal of the PWM converter 5, and a single-phase diode rectifier 9 is connected in parallel to the DC capacitor 6.
The PWM converter 5 is a switching element S1 which can be turned on and off.
A three-phase bridge circuit in which diodes D1 to D6 are respectively connected in parallel to S6 is formed, and switching elements S1 to S6 are turned on / off by a trigger signal V _G generated by the control circuit shown in FIG. 3 to perform harmonic control. It is a thing. The AC reactor 4 and the capacitor 8 are LC filters for suppressing switching ripples, and may be omitted when the switching frequency of the PWM converter 5 is high.

Such a harmonic suppression circuit has an LC filter 3
Part, transformer 7, AC reactor 4, capacitor 8,
The PWM converter 5, the DC capacitor 6, the single-phase diode rectifier circuit 9, and the control circuit shown in FIG. 3 are main components.

When the LC filter 3 is operated as a phase advancing capacitor and the PWM converter 5 is operated as zero impedance with respect to the fundamental wave, the fundamental wave voltage is not applied to the PWM converter 5.

For the harmonics, the PWM converter 5
Generates a harmonic voltage so as to block the harmonic component of the power supply current, and can suppress the problem of the LC filter 3, such as anti-resonance and the inflow of the harmonic current from the host system.

Therefore, here, the concept of real power and imaginary power is introduced by performing three-phase to two-phase conversion, and this will be described in detail using the following mathematical expressions.

First, the three-phase power supply currents I _SU , I _SV , and I _SW and the power supply voltages V _U , V _V , and V _W are converted into two-phase currents Is α, Is β, and two powers by the following equations (1) to (3). Convert to phase voltages Vα and Vβ.

[Equation 1] Here, [C] is a three-phase to two-phase conversion matrix.

From the two-phase voltage and current obtained by the equations (1) to (3), the instantaneous actual power P and the imaginary power Q are obtained by the following equation (4).

[Equation 2]

The electric powers P and Q correspond to conventional active power and reactive power, respectively, and the instantaneous actual power P and imaginary power Q are the direct current component P as expressed by the following equations (5) to (6). It is decomposed into _DC and Q _DC and AC components P _AC and Q _AC .

## EQU3 ## P = P _DC + P _AC (5) Q = Q _DC + Q _AC (6) where the fundamental wave component of the two-phase power supply current Isα, Isβ is the DC component P
_DC and Q _DC are converted into harmonic components, and _{AC components} P _AC and Q _AC are converted into higher harmonic components. In reality, the direct current component and the alternating current component are separated by a high pass filter.

In FIG. 3, 101 is a P, Q arithmetic circuit, 102
Is a high-pass filter, 103 is a current command value calculation circuit, 104
Is an amplifier circuit, 105 is a triangular wave generation circuit, and 106 is a voltage control circuit. The P and Q arithmetic circuits 101 are connected to system voltages V _U , V _V ,
From the detection values of V _W and the power supply currents I _SU , I _SV , and I _SW , equation (1)
According to (2), the instantaneous real power P and the instantaneous imaginary power Q are calculated and output to the high pass filter 102. High-pass filter 102 to remove DC component, the current command calculation circuit 10 as an instantaneous real power of the AC component P _AC and instantaneous imaginary power Q of the AC component Q _AC real power command signal respectively P ^* and imaginary power command signal Q ^*
Send to 3.

[Formula 4] P ^* = P _AC (7) Q ^* = Q _AC (8)

The current command value calculation circuit 103 uses the actual power command signal P ^{*, the} imaginary power command signal Q ^*, and the system voltages V _U , V _V , V.
_In response to _W , the two-phase current command signal is obtained according to formula (1) and the following formulas (9) to (11), and further two-phase to three-phase conversion is performed according to formula (10) to generate a three-phase current command. The signals I _U ^* , I _V ^* , and I _W ^* are generated and sent to the amplifier circuit 104.

[Equation 5] Note that [C] ⁻¹ is the inverse matrix of [C].

The amplifier circuit 104 uses the current command signals I _U ^* , I _V
^* , I _W ^* are input, gain is multiplied by K, and voltage command signal V _U
^* , V _V ^* , and V _W ^* are generated and output to the voltage control circuit 106.

The voltage control circuit 106 is a triangular wave generation circuit 105.
The triangular wave carrier voltage St output from the above and the voltage command signals V _U ^* , V _V ^* , V _W ^* are input, and the voltage command signal V _t is input.
_{If U} ^* ≥ triangular wave carrier voltage S _t , switching element S
1 is turned on, the switching element S6 is turned off, and if the voltage command signal V _U ^* <triangular wave carrier voltage _St , the switching element S1 is turned off and the switching element S6 is turned on.

If the voltage command signal V _V ^* ≧ triangular wave carrier voltage S _t , a trigger signal V _G for turning on the switching element S3 and turning off the switching element S2 is generated. The trigger signal V _G turns the switching elements S1 to S6 on and off, and controls the instantaneous voltage value of each phase of the PWM converter 5.

[0019]

In the passive combined active filter shown in FIG. 2, the control unit shown in FIG. 3 calculates the equations (1) to (11) to obtain the voltage command signals V _U ^* and V _V ^*. , V _W ^* , the voltage command signals V _U ^* , V _V ^* , V _W ^* include the fundamental wave component when the load 2 is unbalanced.

Therefore, the fundamental wave must flow through the three-phase PWM converter 5 to increase the capacity. The present invention seeks to improve this point.

[0021]

The present invention has been made in view of the above points, and in particular, by providing an arithmetic circuit for detecting an anti-phase current component, an anti-phase voltage component from a conventional voltage command signal can be obtained. Is subtracted to form a new voltage command signal.

[0022]

The present invention has the above-mentioned solution, and particularly introduces the concept of the anti-phase real power R and the anti-phase imaginary power S. Here, the instantaneous actual power P and the imaginary power Q-divided two-phase current commands Iα ^* and Iβ ^* are previously calculated by the equations (1) to (9).

Next, using the two-phase voltage and current obtained by the equations (1) to (3), the anti-phase actual power R and the imaginary power S are obtained by the equation (4 ').

[Equation 6]

The anti-phase real power R and the imaginary power S are decomposed into direct current components R _DC and S _DC and alternating current components R _AC and S _AC by the following equations (5 ') and (6'), respectively.

[Equation 7] R = R _DC + R _AC (5 ') S = S _DC + S _AC (6')

Here, from the DC component R _DC of the antiphase real power and the DC component S _{DC of the} imaginary power,

## EQU00008 ## The reverse-phase real power command signal R ^* and the imaginary power command signal S ^* are obtained as R ^* = R _DC (12) S ^* = S _DC (13).

Further, according to the following equation (9 '), the two-phase current command Id corresponding to the reverse-phase actual power R and the imaginary power S is biaxially converted from the reverse-phase actual power command signal R ^* and the imaginary power command signal S ^{*. *} , Iq ^*
To get Two-phase current command for these reverse phase real power R and imaginary power S
Id ^* and Iq ^* are P and Q two-phase current command signals Iα ^* and Iβ.
It is the negative-phase current component existing in ^* .

Further, each phase compensation current command signal I _CU ^* , I _CV ^* , I _CW ^* derived according to the equation (10 ') is a signal for eliminating only the harmonic of each phase not including the fundamental wave component. is there.

[Equation 9] Note that [C] ⁻¹ is given by the equation (11).

The phase compensation current command signals I _CU ^* , I _CV ^* , I _CW ^* obtained in this way are multiplied by the gain K to generate voltage command signals V _U ^* , V _V ^* , V _W ^* . Then, by controlling ON / OFF of the switching element of the PWM converter as compared with the triangular wave carrier voltage, harmonic compensation of the unbalanced load current can be performed.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a control circuit of a passive combined active filter to which the present invention is applied. 107 is an R / S arithmetic circuit, 108 is a low pass filter, 109 is an R / S minute current command value arithmetic circuit. 110 is a three-phase command value calculation circuit, 111 is a P and Q component current command value calculation circuit, and the same symbols as those in FIG. 3 indicate the same components.

P, Q arithmetic circuit 101, high-pass filter 10
2, and P, Q component current command value calculation circuit 111 is expressed by equation (1)
By (9), P and Q two-phase current command signals Iα ^* and Iβ
Output ^* to the three-phase command value calculation circuit 110.

R, S arithmetic circuit 107, low-pass filter 10
8, the R, S component current command calculation circuit 109 uses the equations (1) to (3),
By the formulas (4 ′) to (6 ′), the formulas (12), (13) and the formula (9 ′), P,
Q-phase two-phase current command Id ^* and Iq ^* are calculated as three-phase command calculation circuit 110
Output to.

The three-phase command calculation circuit 110 uses the two-phase current commands Iα ^* and Iβ ^{* for} P and Q and the two-phase current commands Id ^* and Iq for R and S.
By inputting ^* , each phase compensation current command I _CU ^* , I _CV ^* , I _CW ^* is generated according to the equation (10 ′) and output to the amplifier circuit 104.

The amplifier circuit 104 uses the phase compensation current command I _CU ^* ,
I _CV ^* and I _CW ^* are input, the gain is multiplied by K to generate voltage command signals V _U ^* , V _V ^* and V _W ^*, which are output to the voltage control circuit 106.

The voltage control circuit 106 is a triangular wave generation circuit 105.
Output triangular wave carrier voltage S and voltage command signal V
_U ^*, _V V ^*, and enter the V _W ^*, and generates a trigger signal V _G of the switching elements S1~S6 of PWM converter 5. Switching element by a trigger signal V _G S1 to
S6 is turned on and off, and the instantaneous voltage value of each phase of the PWM converter 5 is controlled.

[0035]

As described above, according to the present invention,
By subtracting the R, S component two-phase current command obtained from the anti-phase actual power and the imaginary power from the P, Q component two-phase current command obtained from the instantaneous actual power and the imaginary power of the conventional method, the fundamental wave component is obtained. Since it is possible to obtain a voltage command that does not include PWM
It is possible to perform harmonic compensation of the system while keeping the capacity of the converter small.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a control circuit for a passive combined active filter to which the present invention is applied.

FIG. 2 is a main circuit configuration diagram of a passive combined active filter.

FIG. 3 is a block diagram of a control circuit of the passive combined active filter of FIG.

[Explanation of symbols]

1 Three-phase AC system power supply 2 Load of thyristor Leonard device 3 LC filter 31, 33, 37 Capacitor 32, 34, 36 Reactor 35 Resistor 4 AC reactor 5 PWM converter 6 DC capacitor 6 7 (Y-Y) transformer 8 Capacitor 9 Single-phase diode rectifier 9 101 P, Q calculation circuit 102 High-pass filter 103 Current command value calculation circuit 104 Amplification circuit 105 Triangular wave generation circuit 106 Voltage control circuit 107 R, S calculation circuit 108 Low-pass filter 109 R, S minute current command value arithmetic circuit 110 three-phase command value calculation circuit 111 P, Q current command value calculation circuit D1~D6 diode I _SU, I _SV, I _SW three phases of the power source current I _FU, I _FV, I _FW filter current I _LU, I _LV, I _LW load current Isarufa, current Isβ biphasic ^{_{I U *, I V *,}} I W * the three-phase current command signal Iα ^*, Iβ ^* instantaneous real power P and an imaginary power Q component two-phase current command Id ^* , Iq ^* Reverse phase real electric Two-phase current command I _CU ^* , I _CV ^* , I _CW ^{* for} each force R and imaginary power S Compensation current command signal for each phase P Instantaneous actual power P _DC Instantaneous actual power DC component P _AC Instantaneous actual power AC component P ^* Actual power command signal Q Instantaneous imaginary power Q _DC Direct current component of instantaneous imaginary power Q _AC Instantaneous imaginary power AC component Q ^* Virtual power command signal R Reversed phase actual power R _DC Reversed phase Actual power DC component R _AC Reversed phase actual AC component of power R ^* Reverse phase actual power command signal S Reverse phase imaginary power S _{DC DC component of} reverse phase imaginary power S _{AC AC component of} reverse phase imaginary power S ^* Reverse phase imaginary power command signal S _t Triangular wave carrier voltage S1 ~ S6 Switching element that can be turned on and off V _G Trigger signal V _U , V _V , V _W Three-phase power supply voltage Vα, Vβ Two-phase voltage V _U ^* , V _V ^* , V _W ^* Voltage command signal

Claims (1)

[Claims] 1. A LC connected to a power system in parallel with a load facility.
In a control circuit of a passive-combined active filter in which a filter and a PWM converter are connected in series, the control circuit detects a power supply current and detects an instantaneous real power and an imaginary power from an AC component of the instantaneous real power and the instantaneous imaginary power. A means for outputting a power current command value; a means for detecting the power supply current and outputting a negative phase actual power and imaginary power current command value from a direct current component of the negative phase actual power component and the antiphase imaginary power component; Means for obtaining a three-phase current command value that does not include a fundamental wave component by taking the difference between each of the actual power and imaginary power current command values and the opposite-phase actual power and imaginary power current command values, and gaining the three-phase current command values A control circuit for a passive combined active filter comprising means for multiplying K to obtain a voltage command value.