JP3504007B2 - Active filter control method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls an injection circuit type active filter for reducing a harmonic voltage component by generating a compensation current proportional to a harmonic voltage component contained in a bus voltage and acting as an equivalent resistance. The present invention relates to a method and an apparatus.

[0002]

2. Description of the Related Art In recent years, electric products having a power conversion device using a semiconductor element such as an inverter air conditioner have become widespread, and accordingly, harmonic interference frequently occurs.
Therefore, the number of cases in which an active filter (active filter) is introduced as a countermeasure against harmonics is increasing.
One specific example will be described below with reference to FIG. The above specific example is an injection circuit system that also serves to improve the power factor as well as harmonic compensation. In the figure, (1) is a power supply, (2) is a load, (3) is a system bus, and (4) is an active filter (hereinafter referred to as AF It is called). The power source (1) is connected to a load (2) which is a harmonic generation source via a system bus (3). AF
In (4), the transformer (5) that detects the bus voltage (Vs) at the installation point (P), the capacitor (Ca) and the reactor (La) are connected in series, and the capacitor side becomes the system bus (3). The injection circuit part (6) connected, the high frequency inverter (7) whose output side is connected to the series connection point of the capacitor (Ca) and the reactor (La), and the current transformer (8) for detecting the inverter output current (Ii). ) And the harmonic voltage component (Vn) to be compensated for from the bus voltage (Vs), and the inverter (7) outputs the compensation current (Ia) proportional to the harmonic voltage component (Vn) accordingly. And a control unit (9) for driving and controlling the inverter (7). (10) is the system bus (3)
The system impedance seen from, and its impedance value is (Zs).

In the injection circuit section (6), by selecting, for example, ωLa = 0.08 (1 / ωCa) for the commercial frequency (ω), the fundamental wave voltage applied to the inverter (7) can be greatly reduced. . In this case, most of the power supply voltage is the low frequency fundamental wave (50, 60Hz), so a voltage drop mainly occurs due to the system current in the capacitor (Ca), and the capacitor (Ca) accounts for most of the power supply voltage. For example, only 8% of the power supply voltage is applied to the inverter (7) by sharing it.
Therefore, the inverter (7) only needs to generate 8% of the fundamental wave, and the capacity increase is small compared to the case where only the harmonic wave is generated, and the inverter capacity can be reduced. Since the injection circuit section (6) acts as a fixed parallel-advancing capacitor for the fundamental wave component, it acts as an equivalent to a power factor improving capacitor. Therefore, the capacity of the capacitor (Ca) is set in consideration of a size that facilitates injection of a harmonic current from the inverter (7) to the system bus (3) and an appropriate required phase advance capacity.

In the above structure, first, it is assumed that a harmonic voltage component (Vn) contained in the bus voltage (Vs) causes a harmonic current (In _o ) between the load and the load side. At this time, the harmonic voltage at the installation point (P) is Vs = {Zn / (Zs + Zn)} · Vn.
Therefore, if AF is installed, the bus voltage (Vs) is detected, and the harmonic voltage component (Vn) to be compensated from the voltage (Vs) is detected by the control unit (9), the harmonic voltage component (Vn) A compensation current (Ia) proportional to is generated from the inverter (7). Then, the harmonic voltage component (Vn) and the compensation current (I
AF (4) apparently becomes an equivalent resistance (Ra) at a specific frequency with a) and is connected to the installation point (P). Therefore, for example, if the equivalent resistance (Ra) is set to a value equivalent to the load impedance, a harmonic current (In1) is generated, and at the installation point (P), Vs = {Zp / (Zs + Zp)} · Vn, Zp = {(Zn
Ra) / (Zn + Ra)}, | Zp | <| Zn |, and becomes the harmonic voltage component (V
n) is reduced.

FIG. 3 shows a harmonic equivalent circuit of AF (4). In the figure, the compensation current output from the AF (4) is (Ia), the output current of the inverter (7) is (Ii), the harmonic component of the power supply voltage is (En), the capacitor (Ca) and the reactor (La) at a predetermined order. ) Each reactance of (-X
c) (XL), compensation current (Ia) and bus voltage (V
The harmonic voltage component (Vn) of (s) is
It is represented by the formula (b). (However, j: imaginary unit)

Ia = Ii.jXL / (Zs + jXL-jXc) ... (A)

[0007]   Vn = En ・ {j (XL-Xc)} / {Zs + j (XL-Xc)}-Ii ・ (jXL ・ Zs) / {Zs + j (XL-Xc)}… (b)

In the above equations (a) and (b), the system impedance (Zs) is more than the reactance (XL) (Xc),
When it is small, the equations (a) and (b) are as follows.

[0009] Ia = Ii ・ jXL / (jXL-jXc) = Ii ・ XL / (XL-Xc) ... (C)

Vn = En-Ii ・ {(XL ・ Zs) / (XL-Xc)} ... (d)

At this time, a predetermined compensation current (I
The inverter output current (Ii) that generates a) is Ii = Ia
(jXL-jXc) / jXL = Ia · (XL-Xc) / XL ... (e)

Therefore, when a target equivalent resistance (Ra) is realized for a harmonic of a predetermined order, the inverter output current command value (Ir) is Ir = Ii ... (F) Ra = Vn / Ia ... ( (G) and (e) are set as follows.

[0013]   Ir = Ii = Ia ・ (jXL-jXc) / jXL = Ia ・ (XL-Xc) / XL = (Vn / Ra) ・ (XL-Xc) / XL ...

[Note that {(jXL-jXc) / jXL} = {(XL-Xc) / XL} is the diversion rate (k). ]

Therefore, if the target equivalent resistance (Ra) is first set to a desired value, that value and reactance (-Xc) (XL) are set.
And the measured value (Vn) are used to calculate a command value (Ir), which is input to the control unit (9). Then, when the inverter (7) is driven and controlled by the current control of the control section (9) and the inverter output current (Ii) is made to follow the command value (Ir), a compensation current (Ia) corresponding thereto is generated. Target equivalent resistance (R
A) is realized.

For example, Vn = Ra / (Ra +
Zs)… (ri), and if Ra = (1/2) · Zs, then Vn
= (1/3) · En

Next, FIG. 4 shows a general structure of the control system of the AF (4). In the figure, (5) is a bus voltage transformer, (7) is an inverter, (8) is an inverter output current detection current transformer, (11) is a harmonic voltage detector, (12) is an equivalent resistance part, (13) is a shunt section, (14) is a subtractor, (1
5) is a current controller and (16) is a comparator. The harmonic voltage detector (11) detects a harmonic voltage component (Vn) to be compensated from the bus voltage (Vs) and outputs it. The equivalent resistance part (12) calculates the reciprocal value of the equivalent resistance (Ra) as the harmonic voltage component (V
Multiply n) and calculate the compensation current value you want to achieve. The shunt ratio part (13) multiplies the shunt ratio (k) by the output value of the equivalent resistance part and outputs a command value (Ir) of the inverter output current (Ii) for realizing the desired compensation current (Ia).

The subtractor (14), the current controller (15) and the comparator (16) constitute an inverter controller (21), and the subtractor (1
4) subtracts the inverter output current (Ii) detected by the current transformer (8) and its command value (Ir). The current controller (15) receives the output value of the subtractor as an input value, outputs a control signal for driving the inverter (7) so that the inverter output current (Ii) follows the command value (Ir), and outputs the control signal to the comparator ( 16)
Is converted into a pulse waveform by and applied to the inverter (7).

[0019]

The problem to be solved is to calculate the inverter output current command value (Ir) by
The system impedance (Zs) becomes a value that cannot be ignored with respect to the reactance (-Xc) (XL) of the injection circuit section (6), and is changed to {(jXL-jXc) / jXL} as the diversion rate (k). hand,
When {(Zs + jXL-jXc) / jXL} must be used, the system impedance (Zs) changes depending on the system conditions, and its value cannot be known unless measured, and the measured value Since it is not always accurate, it is not possible to use accurate impedance (Zs).
Therefore, the error becomes very large, and there is a problem that the compensation effect of AF (4) cannot be sufficiently obtained.

[0020]

The present invention provides, as a method,
It has an injection circuit section in which a capacitor and a reactor are connected and the capacitor side is connected to a system bus, and a high-frequency inverter whose output side is connected to the connection point between the capacitor and the reactor in the injection circuit section has a bus voltage Injection for detecting a harmonic voltage component and generating a compensation current proportional to the voltage component from the inverter, and the compensation current acting as an equivalent resistance in relation to the harmonic voltage component to reduce the harmonic voltage component In controlling the circuit type active filter, set the output current command value of the above inverter to Ir = [(1
/ Ra) {1- (Xc / XL)}-(1 / jXL)] ・ Vn (where Ir: inverter output current command value, Ra: equivalent resistance, Xc: capacitor impedance, XL: reactor impedance, Vn:
Harmonic voltage component, j: imaginary unit)

As a device, a high-frequency inverter having an injection circuit section in which a capacitor and a reactor are connected and the capacitor side is connected to a system bus, and an output side is connected to a connection point between the capacitor and the reactor in the injection circuit section. And a harmonic voltage component of the bus voltage is detected, a compensation current proportional to the voltage component is generated from the inverter, and the compensation current acts as an equivalent resistance in relation to the harmonic voltage component. In an injection circuit type active filter control device that reduces harmonic voltage components, connected to the harmonic voltage detector that detects the harmonic voltage component to be compensated from the bus voltage, and the harmonic voltage detector output, and equivalent The reciprocal value of the resistance, the impedance difference between the reactor and the capacitor, and the reciprocal value of the impedance of the reactor are calculated in order of A command value calculation first output unit for multiplying by minutes and a command for connecting the above harmonic voltage detector output in parallel to the first operation unit and outputting the above harmonic voltage component with a 90 ° phase delay. A second calculation unit for calculating a value, a third calculation unit for calculating a command value, which is connected to the output of the second calculation unit and which multiplies the output value by the reciprocal value of the impedance of the reactor and outputs the output value; A command value setting subtractor that inputs three output values of the operation unit, subtracts the output value of the third operation unit from the output value of the first operation unit, and outputs an inverter output current command value, the inverter output current command value, and the inverter output A current is input, and an inverter control unit that drives and controls the inverter to make the inverter output current follow the command value is provided.

[0022]

According to the above technical means, the inverter output current command value is determined by the known target equivalent resistance value, each impedance value of the capacitor and the reactor of the injection circuit section, and the harmonic voltage component of the bus voltage known by the measurement. The inverter output current command value is simply calculated without using the system impedance directly and therefore without depending on the system conditions.

[0023]

1 is a block diagram of an AF control method and apparatus according to the present invention.
And the equivalent circuit of FIG. 3 will be described below. First, an AF control method according to the present invention will be described with reference to the harmonic equivalent circuit shown in FIG. In the figure, as in the conventional case, the inverter output current command value is (Ir), the compensation current is (Ia), the harmonic voltage component of the bus voltage (Vs) is (Vn), the target equivalent resistance of AF is (Ra), If the reactances of the capacitor (Ca) and reactor (La) in a given order are (-Xc) (XL), the current flowing through the reactor (La) is (Ib), and the voltage across its terminals is (Vb), then The (nu) and (ru) expressions hold.

[0024]   Ir = Ia-Ib ... (nu) Vb = Vn-(-jXc) ・ Ia = Vn + (jXc / Ra) ・ Vn ... (ru) (∵Ia = Vn / Ra)

From this, the inverter output current command value (I
r) is given by the following equation (e).

[0026]   Ir = (Vn / Ra)-(Vb / jXL) = [(1 / Ra) {1- (jXc / jXL)}-(1 / jXL)] ・ Vn = [(1 / Ra) {1- (Xc / XL) }-(1 / jXL)] ・ Vn… (e)

Therefore, when the equation (e) is used, the target equivalent resistance (Ra) and the reactance (-Xc) (XL) of the injection circuit section (6) are all known, so that the harmonic voltage component ( By measuring Vn), the system impedance (Z
Therefore, the inverter output current command value (Ir) can be determined easily and accurately without using s). Here, the equation (e) is transformed as follows.

[0028] Ir = (Vn / Ra) ・ {1- (Xc / XL)-(Ra / jXL)}… (wa)

Then, in the equation (wa), the term {1- (Xc / XL)} in the first half of {} is the conventional diversion rate (k), and the second half (Ra / jXL) is the error component. . Therefore, the reactor (L
It is known that the error decreases as the reactance (XL) of a) is increased and the equivalent resistance (Ra) is decreased for the purpose of increasing the compensation current (Ia).

Next, an embodiment of an AF control device according to the present invention will be described with reference to FIG. In the figure, (3) is a system bus, (5) is a bus voltage transformer, (7) is an inverter, (8) is an inverter output current detection current transformer, and (11).
Is a harmonic voltage detector, (14) is a subtractor (corresponding to a conventional inverter control subtractor), (15) is a current controller,
(16) is a comparator, (21) is an inverter control unit composed of a subtractor (14), a current control unit (15) and a comparator (16), (17) is a first operation unit, (18) Is the second computing unit, (19)
Is a third operation unit, and (20) is a subtractor. The difference from the conventional AF control system shown in FIG. 2 is that the equivalent resistance section (12) and the shunt section (13) are replaced by first, second and third calculation sections (17).
This is because the inverter output current command value (Ir) was calculated from the harmonic voltage component (Vn) based on the equation (e) using (18), (19) and the subtractor (20).

The first arithmetic unit (17) is connected to the output of the harmonic voltage detector (11) and outputs (1 / Ra) .multidot. ((XL) to the harmonic voltage component (Vn) of the bus voltage (Vs). -Xc) / XL} and multiply (Vn / Ra)
Output {(XL-Xc) / XL}. The second operation unit (18) is connected to the output of the harmonic voltage detector (11) in parallel with the first operation unit (17), and the harmonic voltage component (Vn) of the bus voltage (Vs) is 90 °.
The phase is delayed and (Vn / j) is output. The third calculation unit (19) multiplies the output value (Vn / j) of the second calculation unit by (1 / XL) and outputs (Vn / jXL). The subtractor (20) expresses each output value (Vn / Ra) · {(XL-Xc) / XL} and (Vn / jXL) of the first and third operation units (17) and (19) as the expression (E). The inverter output current command value (Ir) is calculated by subtraction based on That is, through the above calculation, the inverter output current command value (Ir) is

Ir = (Vn / Ra) * {(XL-Xc) / XL}-(Vn / jXL) = [(1 / R
a) {1- (Xc / XL)}-(1 / jXL)] · Vn, which matches the equation (e).

Therefore, as in the conventional case, the subtracter (14) subtracts the inverter output current (Ii) and its command value (Ir), and the inverter ( When the inverter output current (Ii) is made to follow the command value (Ir) by driving and controlling 7), the compensation current (Ia) that realizes the target equivalent resistance (Ra) is correspondingly generated from the AF according to the present invention. Is output.

In the above embodiment, AF is equivalent resistance (R
Although the inverter output current command value (Ir) is calculated from the target equivalent resistance value of the AF, the AF may be operated with an arbitrary equivalent impedance (Za).
In that case, instead of the equivalent resistance (Ra), the inverter output current command value (Ir) may be calculated from the target equivalent impedance (Za) in the same manner by the calculation processing of the equation (e).

[0035]

According to the present invention, a control of an injection circuit type active filter for reducing the above harmonic voltage component by generating a compensating current proportional to the harmonic voltage component contained in the bus voltage and acting as an equivalent resistance. In, the inverter output current command value was calculated with the known target equivalent resistance value, each impedance of the capacitor and reactor of the injection circuit section, and the harmonic voltage component of the bus voltage known by the measurement, and thus the system impedance is directly used. Therefore, the inverter output current command value can be calculated easily and accurately irrespective of the system condition, and the compensation effect of the active filter can be stably and reliably obtained.

[Brief description of drawings]

FIG. 1 is a principal block diagram showing an embodiment of a control device for an active filter according to the present invention.

FIG. 2 is a block diagram showing an example of a conventional active filter.

FIG. 3 is a circuit diagram showing a harmonic equivalent circuit of an active filter.

FIG. 4 is a main part block diagram showing an example of a conventional active filter control device.

[Explanation of symbols] 3 system bus 7 inverter 11 Harmonic voltage detector 17 First operation unit 18 Second operation unit 19 Third operation unit 20 subtractor 21 Inverter controller Vs Bus voltage Vn Harmonic voltage component Ir inverter output current command value Ii Inverter output current

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsufusa Mizuki 47 Umezu Takaunecho, Ukyo-ku, Kyoto City, Nissin Electric Co., Ltd. (58) Fields investigated (Int.Cl. ⁷ , DB name) H02J 3 / 00-5/00

Claims (2)

(57) [Claims] 1. An injection circuit unit comprising a capacitor and a reactor connected to each other and a capacitor side connected to a system bus, and a high frequency inverter having an output side connected to a connection point between the capacitor and the reactor of the injection circuit unit. Then, a harmonic voltage component of the bus voltage is detected, and a compensation current proportional to the voltage component is generated from the inverter, and the compensation current acts as an equivalent resistance in relation to the harmonic voltage component to generate the above-mentioned harmonic voltage. In controlling the injection circuit type active filter for reducing the component, the output current command value of the inverter is Ir = [(1 / Ra) {1- (Xc / XL)}-(1 / jXL)]. Vn ( However, Ir: Inverter output current command value, Ra: Equivalent resistance, Xc: Impedance of capacitor, XL: Impedance of reactor, Vn: Harmonic voltage component, j:
A method for controlling an active filter, which is characterized in that it is set by an imaginary unit. 2. An injection circuit section comprising a capacitor and a reactor connected to each other and a capacitor side connected to a system bus, and a high frequency inverter having an output side connected to a connection point between the capacitor and the reactor of the injection circuit section. Then, a harmonic voltage component of the bus voltage is detected, and a compensation current proportional to the voltage component is generated from the inverter, and the compensation current acts as an equivalent resistance in relation to the harmonic voltage component to generate the above-mentioned harmonic voltage. In a control device for an injection circuit type active filter that reduces the component, it is connected to the harmonic voltage detector that detects the harmonic voltage component to be compensated from the bus voltage, and the output of the above harmonic voltage detector. Numerical value, impedance difference between reactor and capacitor, and inverse numerical value of reactor impedance are sequentially multiplied by the above harmonic voltage component and output. And a second command value calculation second calculation unit that is connected in parallel to the output of the higher harmonic voltage detector to the first calculation unit and outputs the higher harmonic voltage component with a 90 ° phase delay. An arithmetic unit, a third arithmetic unit for command value calculation, which is connected to the output of the second arithmetic unit and which multiplies the output value by the inverse value of the impedance of the reactor and outputs the output value, and the output values of the first and third arithmetic units. Is inputted, the subtracter for setting the command value for subtracting the third calculation unit output value from the first calculation unit output value to output the inverter output current command value, and the inverter output current command value and the inverter output current are inputted, An active filter control device comprising: an inverter control unit that drives and controls the inverter to cause an inverter output current to follow the command value.