JPH07142958A - Active filter and its controller - Google Patents

Abstract

PURPOSE:To provide an active filter capable of absorbing the higher harmonic up to a high frequency by combining a current shape converter needing no AC reactor on an output side and a capacitor bypassing a higher harmonic current. CONSTITUTION:This active filter is provided with capacitors 5 to 17 bypassing at least higher harmonic current and provided between and AC power source 1 and a higher harmonic generation source 8, the current shake converter 9 composed by bridge-connecting self arc-extinction switching elements 10 to 33 and connecting a DC reactor between its DC terminals and a control means detecting the higher harmonic component of a current flowing between the AC power source 1 and the capacitors 5 to 7 and controlling the output current of the current shake converter 9 based on the higher harmonic component so as to negate the higher harmonic component generated from the higher harmonic generation source 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a harmonic current from a harmonic source and controls the output current of a current source converter so that the output current matches the harmonic current and has a reverse polarity. The present invention relates to an active filter that improves waveform distortion of a current flowing in a power supply by absorbing a harmonic current from a wave generation source by a current source converter, and a control device therefor.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional active filter. In the figure, 1 is an AC power supply, 8 is a harmonic generation source, 47 to 49 are AC reactors, and 50 is a voltage source converter.

When the harmonic current flowing out from the U-phase of the harmonic generation source 8 is IUH1, if the voltage source converter 50 generates IUH2 which is equal to IUH1 and opposite in polarity, the harmonic current flowing in the AC power supply 1 is It can be zero. However, a voltage drop occurs due to the harmonic current IUH2 flowing through the AC reactor 47. The same applies to the other V and W phases. The voltage drop at this time is proportional to the inductance of the AC reactors 47 to 49 and the magnitude and frequency of the harmonic currents IUH2, IVH2, and IWH2. Therefore, when trying to absorb even higher harmonics, this voltage drop becomes large and the voltage-source converter 50
It is necessary to increase the capacity of. In order to reduce the voltage drop, it is sufficient to reduce the inductance of the AC reactors 47 to 49, but since the harmonic current generated by the switching of the voltage source converter 50 increases, it is necessary to increase the switching frequency. If the switching frequency is increased, the switching loss increases, so there is a limit to the increase of the switching frequency.

[0004]

As described above, in the conventional active filter, since the voltage source converter is used, the AC reactor is required on the output side and the switching frequency is also limited. There was a limit to the harmonics that can be absorbed from.

Therefore, a first object of the present invention is to provide a current source converter which does not require an AC reactor on the output side and a capacitor for bypassing a harmonic current between the AC power source and the harmonic generation source. The purpose of the present invention is to provide an active filter capable of absorbing high frequency harmonics.

A second object of the present invention is to provide a current source converter which does not require an AC reactor on the output side and a capacitor for bypassing a harmonic current between the AC power source and the harmonic generation source. To provide a control device for an active filter that extracts a harmonic component of a current flowing to a power supply with high sensitivity, controls a harmonic current output from a current source converter, and removes a harmonic component flowing to an AC power supply. It is in.

[0007]

In order to achieve the above-mentioned first object, the active filter according to the invention of claim 1 is provided with at least a harmonic current provided between an AC power supply and a harmonic generation source. To cancel the harmonic components generated from the harmonic source generated by connecting a bypass capacitor and a self-extinguishing type switching element in a bridge connection, and connecting a DC reactor between its DC terminals. ,
It is characterized by comprising a control means for detecting a harmonic component of a current flowing between the AC power source and the capacitor and controlling an output current of the current source converter based on the harmonic component. .

Further, in order to achieve the first object, the active filter according to the invention as defined in claim 2 is provided with a capacitor provided between the AC power source and the harmonic generation source for bypassing at least the harmonic current. , A bridge connection of self-extinguishing type switching elements, a DC reactor separately connected between each DC terminal, and a multiple current type converter in which the AC side terminals are commonly connected, and the harmonics generated from the harmonic generation source. In order to cancel the component, a control means for detecting a harmonic component of a current flowing between the AC power source and the capacitor and controlling an output current of the multiple current type converter based on the harmonic component is provided. It is characterized by that.

Further, in order to achieve the above-mentioned second object,
According to another aspect of the present invention, there is provided a control device for an active filter, wherein an AC power supply, a capacitor provided between a harmonic generation source and bypassing at least a harmonic current, and a self-extinguishing type switching element are bridge-connected. A current source converter formed by connecting a DC reactor between its DC terminals, a three-phase to two-phase conversion means for converting a three-phase current flowing between the AC power supply and the capacitor into two phases, and the AC power supply voltage Phase detecting means for detecting a phase angle, and first output for converting the output of the three-phase to two-phase converting means into a direct current amount which is a coordinate amount that rotates in synchronization with the phase angle detected by the phase detecting means.
Coordinate conversion means, means for detecting the change rate of the output of the first coordinate conversion means, and output of the means for detecting the change rate rotate in synchronization with the phase angle detected by the phase detection means. The present invention is characterized in that a second coordinate conversion means for converting into an alternating current amount is provided, and the output current of the current source converter is controlled according to the output of the second coordinate conversion means.

Furthermore, in order to achieve the above-mentioned second object, the control device for the active filter according to the invention of claim 4 is provided with at least a harmonic current provided between the AC power source and the harmonic generation source. A bypassing capacitor and a self-extinguishing type switching element in a bridge connection, a DC reactor is separately connected between each DC terminal, and a multiple current type converter in which the AC side terminals are commonly connected, the AC power supply and the Three-phase to two-phase conversion means for converting three-phase current flowing between capacitors into two phases, phase detection means for detecting a phase angle of the AC power supply voltage, and output of the three-phase to two-phase conversion means to the phase First coordinate conversion means for converting into a DC amount which is a coordinate amount that rotates in synchronization with the phase angle detected by the detection means, and means for detecting the rate of change of the output of the first coordinate conversion means. , This strange A second coordinate conversion means for converting the output of the rate detecting means into an alternating current amount that rotates in synchronization with the phase angle detected by the phase detecting means is provided, and according to the output of the second coordinate converting means. The output current of the multi-current type converter is controlled.

[0011]

The active filter according to the first aspect of the invention is
The harmonic component generated from the harmonic generation source is canceled by the harmonic current output from the current source converter to prevent the harmonic current from flowing to the AC power supply.

According to the second aspect of the present invention, in the case where the harmonic component generated from the harmonic generation source is canceled by the harmonic current output from the current source converter, the current source converter uses multiple currents. Since it is a shape converter, it can finely remove the harmonic components and prevent the harmonic current from flowing to the AC power supply.

According to a third aspect of the present invention, an active filter control device detects a current flowing between an AC power supply and a capacitor, and detects the current and rotates the current in synchronization with the phase angle of the AC power supply voltage vector. By converting the output to the AC power supply and the capacitor, the harmonic component of the current flowing between the AC power supply and the capacitor can be easily extracted, and the output current of the current source converter can be controlled based on this harmonic component. The harmonic current is suppressed from flowing into the AC power supply.

According to a fourth aspect of the present invention, an active filter control device detects a current flowing between an AC power supply and a capacitor, and detects the current and rotates it in synchronization with a phase angle of an AC power supply voltage vector. By converting the output to the change rate and then detecting the rate of change, the harmonic components of the current flowing between the AC power supply and the capacitor can be easily extracted, and the output current of the multiple current converter can be finely controlled based on this harmonic component. The harmonic current is suppressed from flowing into the AC power supply.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is an AC power supply, 2 to 4 are AC reactors, 5 to 7 are capacitors for bypassing harmonic currents, and 8 is a harmonic generation source. Reference numeral 9 is a current source converter, and 10 to 33 are switching elements forming the current source converter 9, which are self-turn-off elements such as GTO. Further, the switching elements 10 to 15 configure a first bridge, the switching elements 16 to 21 configure a second bridge, the switching elements 22 to 27 configure a third bridge, and the switching elements 28 to 33 configure a fourth bridge. To do. Reference numerals 34 to 37 denote DC reactors that smooth the DC currents of the first to fourth bridges, respectively. 38, 39, 40 are U phase, V phase, W respectively
The phase current detector 41 is a three-phase to two-phase converter. 42
Is a phase detection circuit for detecting the phase angle of the voltage. Reference numeral 43 is a coordinate converter that converts the output of the three-phase to two-phase converter 41 into a coordinate amount that rotates in synchronization with the phase angle of the voltage detected by the phase detection circuit 42. A differentiating circuit 44 detects the rate of change of the output signal of the coordinate converter 43. Reference numeral 45 is a coordinate converter that converts the output signal of the differentiating circuit 44 into the original stationary coordinates. 46 is a two-phase to three-phase converter.

Next, the operation of the embodiment of the present invention having the above-mentioned structure will be described with reference to the waveform diagram of FIG. 2 showing the operation of the present invention. In the figure, IHU is a current flowing in the U phase of the harmonic generation source 8. In the V phase and the W phase, currents having the same waveform with a phase delay of 120 ° each flow. A 12-phase controlled rectifier is assumed as the harmonic generation source.

IU is a U-phase current flowing between the capacitors 5 to 7 and the power supply 1. In the V phase and the W phase, currents having the same waveform with a phase delay of 120 ° each flow. VUV is the UV line-to-line voltage of capacitors 5-7. The VW-phase and WU-phase line voltages also have the same waveform with a phase delay of 120 ° each. IFU is a current flowing in the U phase of the current source converter 9. In the V phase and the W phase, currents having the same waveform with a phase delay of 120 ° each flow. IU, IV, IW are detected by the current detectors 38, 39, 40, and the three-phase to two-phase converter 41 is composed of an adder and a multiplier.

[0018]

[Equation 1] IA = IU- (IV + IW) / 2 IB = (IV-IW) * 1.732 / 2 is calculated and IU, IV, IW on U, V, W coordinates
Is converted into IA and IB on the A and B coordinates. However, the A axis is an axis parallel to the U axis, and the B axis is an axis advanced by 90 ° with respect to the A axis. The waveforms of IA and IB are shown in FIG. The outputs IA and IB of the three-phase to two-phase converter 41 are input to the coordinate converter 43. The coordinate converter 43 is composed of a sine function,

[0019]

[Equation 2] ID = IA * COS (-TH) -IB * SIN (-TH) IQ = IB * COS (-TH) + IA * SIN (-TH) calculation, IA on A, B coordinates, IB is converted into an amount on the D and Q coordinates that rotates in synchronization with the phase angle TH of the voltage. Waveforms of ID and IQ are shown in FIG. As can be seen from the figure, since the fundamental wave of ID and IQ is DC, ID and IQ are
IU, IV, IW can be easily detected by detecting the change rate of
It is possible to extract the harmonic component contained in. ID,
The IQ is added to the differentiating circuit 44, and the rate of change of ID is RIFD
RIFQ is detected with the IQ change rate. The RIFD waveform is shown in FIG. RIFQ is 90 ° to RIFD
A similar waveform with a delayed phase is obtained. Input RIFD and RIFQ to the coordinate converter 45,

[0020]

[Equation 3] RIFA = RIFD * COS (TH) -RIFQ * SIN (TH) RIFB = RIFQ * COS (TH) + RIFD * SIN (TH) is calculated, and D rotates in synchronization with the phase angle TH of the voltage. , RIDF and RIFQ on the Q coordinate are returned to RIFA and RIFB on the A and B coordinates, which are the original stationary coordinates. R
The waveform of IFA is shown in FIG. RIFB has a similar waveform with a 90 ° phase delay with respect to RIFA. RIFA, R
The IFB is input to the two-phase to three-phase converter 46. The two-phase to three-phase converter 46 is composed of an adder and a multiplier,

[0021]

[Equation 4] RIFU = RIFA / 1.5 RIFV = (-0.5 * RIFA + 0.866 * RIFB) /1.5 RIFW = (-0.5 * RIFA-0.866 * RIFB) /1.5 is calculated, and RIFA on A and B coordinates, The RIFB is converted into RIFU, RIFV, and RIFW on U, V, and W coordinates. The RIFU waveform is shown in FIG. RIFV, RI
The FW has a similar waveform with a phase delay of 120 ° with respect to the RIFU. RIFU, RIFV, RIF obtained at the output of the two-phase to three-phase converter 46 as described above
The output current of the current source converter 9 is controlled based on W. IFU is a U-phase current of the current source converter 9 controlled by using RIFU as a reference value. The V-phase current and the W-phase current are similarly controlled.

In the above description, the operation waveforms are shown for the case where the current source converter 9 is composed of four bridges. Therefore, the output current of the current source converter 9 has a four-step waveform as shown by IFU. By increasing the number of bridges, the output current waveform can be controlled more finely. Conversely, it is possible to reduce the number of bridges, and it is possible to operate with one bridge. When the number of bridges is 1, the output current waveform has a one-step pulse width controlled waveform. The harmonics contained in the output current are bypassed by the capacitors 5 to 7 and do not flow out to the power supply side.

In the embodiment, the AC power source 1 and the capacitor 5 are also included.
Although the example in which the AC reactors 2 to 4 are provided between 7 to 7 has been described, the AC reactors 2 to 4 can be omitted when the AC power supply 1 has a reactor element such as a transformer.

[0024]

As described above, in the active filter according to the first aspect of the present invention, the capacitor for bypassing the harmonic current and the self-extinguishing type switching element are bridge-connected, and the DC reactor is connected between the DC terminals. It is configured to combine with a connected current source converter, and by controlling the output current of the current source converter, the harmonic components generated from the harmonic generation source are reduced. (1) Since the current source converter can control the output current stepwise at a fast rate of change, it can absorb high harmonic components. (2) The current source converter does not require an AC reactor on the output side, unlike the voltage source converter, so there is no voltage drop due to harmonic current. Therefore, it is not necessary for the converter to generate a high voltage against the voltage drop, so that the capacity of the converter can be reduced. (3) By connecting the harmonic source, the current source converter, and the capacitor in parallel, the fast harmonic components generated by the harmonic source and the current source converter can be bypassed by the capacitor.

The effects such as the above can be obtained. In the active filter according to the second aspect of the present invention, a capacitor that bypasses a harmonic current and a self-extinguishing type switching element are bridge-connected, and a DC reactor is separately connected between each DC terminal, and an AC-side terminal is provided. It is configured by combining with a commonly connected multiple current type converter, and by controlling the output current of the multiple current type converter, the harmonic components generated from the harmonic generation source are reduced. From
In addition to the above-mentioned effects, since fine control is possible, the current on the AC power supply side can be controlled in a more sinusoidal manner.

Further, in the control device for the active filter according to the third aspect of the present invention, the capacitor for bypassing the harmonic current and the self-extinguishing type switching element are bridge-connected, and the DC reactor is connected between the DC terminals. In the active filter configured by combining the current source converter, the current flowing between the AC power supply and the capacitor is converted into an amount on the coordinate that rotates in synchronization with the phase angle of the power supply voltage vector, and then the change rate is detected. Since the harmonic component is detected by the high-frequency component, the harmonic component of the current flowing to the AC power supply can be extracted with high sensitivity, so that the harmonic can be effectively reduced.

Further, in the control device for the active filter according to the present invention, the capacitor for bypassing the harmonic current and the self-extinguishing type switching element are bridge-connected, and the DC reactors are separately provided between the DC terminals. In the active filter that is configured by combining multiple current source converters that are connected to each other and the AC side terminals are commonly connected, the current that flows between the AC power supply and the capacitor is rotated in synchronization with the phase angle of the power supply voltage vector. Since the change rate is detected and the harmonic component is detected after conversion into the amount of, the harmonic component of the current flowing to the AC power supply can be extracted with high sensitivity.
The current IHU of the harmonic generation source in FIG. 2 and the current I flowing to the power supply
As can be seen by comparing U, higher harmonics can be reduced more effectively than in the control device for an active filter according to the third aspect of the invention.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a control circuit showing an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of one embodiment of the present invention.

FIG. 3 is a configuration diagram showing an embodiment of a conventional device.

[Explanation of symbols]

1 ... Power supply 2-4 ...
AC reactor 5-7 ... Capacitor 8 ...
Harmonic source 9 Current source converter 10-33
Switching elements 34-37 ... DC reactors 38-40 ...
Current detector 41 ... Three-phase to two-phase converter 42 ...
Phase detection circuit 43 ... Coordinate converter 44 ...
Differentiating circuit 45 ... Coordinate converter 46 ...
Two-phase to three-phase converter 47-49 ... AC reactor 50 ...
Voltage source converter

Claims (4)

[Claims] 1. A self-extinguishing type switching element is bridge-connected with a capacitor provided between an AC power source and a harmonic generation source to bypass at least a harmonic current, and a DC reactor is connected between its DC terminals. In order to cancel the harmonic components generated from the current source converter and the harmonic generation source, the harmonic components of the current flowing between the AC power supply and the capacitor are detected, and the harmonic components are detected. An active filter comprising control means for controlling the output current of the current source converter based on the above. 2. A self-extinguishing type switching element and a capacitor provided between an AC power source and a harmonic generation source for bypassing a harmonic current, and a self-extinguishing type switching element are bridge-connected, and a DC voltage is separately provided between each DC terminal. A multiple current type converter in which a reactor is connected and AC terminals are commonly connected, and a harmonic of a current flowing between the AC power supply and the capacitor to cancel a harmonic component generated from the harmonic generation source. An active filter comprising control means for detecting a component and controlling the output current of the multiple current type converter based on the harmonic component. 3. A capacitor, which bypasses at least a harmonic current, provided between an AC power source and a harmonic generation source, and a self-extinguishing type switching element are bridge-connected, and a DC reactor is connected between the DC terminals. A current source converter, a three-phase → two-phase conversion means for converting a three-phase current flowing between the AC power supply and the capacitor into two phases, and a phase detection means for detecting a phase angle of the AC power supply voltage. First coordinate conversion means for converting the output of the three-phase to two-phase conversion means into a direct current amount which is a coordinate amount that rotates in synchronization with the phase angle detected by the phase detection means, and the first coordinate conversion means. Means for detecting the change rate of the output of the coordinate conversion means, and second coordinates for converting the output of the means for detecting the change rate into an alternating current amount that rotates in synchronization with the phase angle detected by the phase detection means. A second seat comprising a conversion means A control device for an active filter, characterized in that the output current of the current source converter is controlled according to the output of the target conversion means. 4. A multi-current converter in which a self-extinguishing type switching element is bridge-connected, a DC reactor is separately connected between respective DC terminals, and AC side terminals are commonly connected. The control device for the active filter according to claim 3, wherein: