JPH10337087A - Single phase-multiphase power converting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the curtailment of switching arms or reactors for ripple absorption to be added to a DC middle circuit. SOLUTION: This power converting circuit has a single-phase converter, a voltage type of inverter which converts the output voltage into multiphase AC voltage so as to drive a multi-phase AC motor, and a smoothing capacitor which is connected to a DC middle circuit. In this case, a capacitor 601 for ripple absorption is connected between the neutral point of the star-connected stator winding of a motor 500 and one hand of the junctions between an inverter 300 and a smoothing capacitor 402. The inverter 300 gives and receives power between itself and a motor 500, and besides it gives and receives zero-phase power between itself and the capacitor 601 at the time of output of zero-voltage vector so as to control DC voltage, whereby this circuits absorbs the power ripple of the DC middle circuit by the capacitor 601.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase AC motor for converting a single-phase AC power into a DC power by a converter, converting the DC power into a polyphase AC power by a voltage type inverter, and driving a polyphase AC motor. More specifically, the present invention relates to a technique for reducing the capacity of a smoothing capacitor provided in a DC intermediate circuit.

[0002]

2. Description of the Related Art FIG. 10 is a paper published in the proceedings of the National Conference of the Institute of Electrical Engineers of Japan, entitled "Reduction of Capacitor Capacity of Single-Phase PWM Converter with 715 DC Active Filter Function".
1 is a prior art of a single-phase to multi-phase power conversion circuit using the circuit configuration described in FIG. In the figure, 100 is a single-phase AC power supply,
Reference numeral 200 denotes a PWM-controlled single-phase full-bridge converter comprising self-extinguishing semiconductor switching elements such as IGBTs and anti-parallel diodes, and 300 denotes a three-phase voltage-source inverter comprising similar self-extinguishing semiconductor switching elements and anti-parallel diodes. , 401 is a two-quadrant chopper, 402
Is a smoothing capacitor provided in the DC intermediate circuit,
Reference numeral 404 denotes a reactor and a capacitor for a filter, and reference numeral 500 denotes a three-phase induction motor as a load. Although a detailed description of the operation of this circuit is omitted, as a basic operation, the AC input current waveform is maintained as a sine wave by the PWM control of the converter 200 and the input power factor is controlled to 1 while
2 of power supply frequency generated on the DC output side of converter 200
In order to absorb the double frequency power ripple, energy is transferred by controlling the voltage of the capacitor 404 by the two-quadrant chopper 401, thereby reducing the capacity of the smoothing capacitor 402.

[0003] Fig. 11 shows a paper "The DC voltage pulsation of a single-phase PWM converter" published in the 1993 Industrial Application Division of the Institute of Electrical Engineers of Japan (vol.113-D, No.9, p.1106 to p.1107). FIG. 12 is a prior art of a single-phase to multi-phase power conversion circuit using the circuit configuration described in “One Suppression Measure”. This is a conventional technique of a single-phase to multi-phase power conversion circuit using a circuit configuration described in “DC power pulsation reduction method of type PWM converter”. In these figures, reference numeral 405 in FIG. 11 denotes an LC filter as a series resonance circuit connected to a DC intermediate circuit,
In FIG. 12, reference numeral 406 denotes a reactor, and other components which are the same as those in FIG. 10 are denoted by the same reference numerals. Although detailed description of the operation of these circuits is omitted, basically,
2 of power supply frequency generated on the DC output side of converter 200
Fig. 1 with double power ripple and same resonance frequency
This is absorbed by the LC filter 405 of one and the reactor 406 of FIG. 12, thereby reducing the capacity of the smoothing capacitor 402.

[0004]

In each of the prior arts shown in FIGS. 10 to 12, a reactor is used for absorbing power ripple, which hinders miniaturization. In addition, in the prior art shown in FIGS. 10 and 12, it is necessary to add one upper and lower arm to the DC intermediate circuit, which hinders downsizing and cost reduction. Further, in the prior art shown in FIG.
There is a problem that the withstand voltage of the capacitor 05 is twice as high as the DC intermediate voltage.

Accordingly, the present invention solves the above-mentioned problems of the prior arts, and achieves a single-phase / multi-phase device capable of reducing the size and cost of a device with a simple circuit configuration and reducing the capacity of a smoothing capacitor. It is intended to provide a phase power conversion circuit.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a converter for converting a single-phase AC voltage to a DC voltage, and a converter for converting the DC voltage to a multi-phase AC voltage. In a single-phase to multi-phase power conversion circuit having a voltage source inverter for driving a phase AC motor and a smoothing capacitor connected to a DC intermediate circuit, a neutral point of a star-connected stator winding of the motor; A ripple absorbing capacitor as an energy storage element is connected between one of the connection points of the inverter and the smoothing capacitor, and the inverter transfers power to and from the electric motor by time division, and the zero by the inverter. By transmitting and receiving zero-phase power to and from the ripple absorbing capacitor at the time of output of the voltage vector, and controlling the DC voltage of the ripple absorbing capacitor, the power of the DC intermediate circuit is reduced. The pull is to absorbed by the ripple absorbing capacitors.

In the above configuration, exchange of AC power between the inverter and the motor is performed in the same manner as in the related art by controlling power using the line voltage of the inverter and the current flowing between the lines. Further, by controlling the zero-phase voltage and the zero-phase current using the zero-voltage vector of the inverter, the same operation as the upper and lower arms added to the DC intermediate circuit in the related art can be performed. Zero-phase power is transmitted and received between the capacitor and the ripple absorbing capacitor of the energy storage element to absorb the power ripple of the DC intermediate circuit. As a result, the conventional additional arm can be reduced, and the conventional reactor for absorbing power ripple can be substituted by the leakage reactance of the AC motor, thereby contributing to downsizing and cost reduction of the device.

According to a second aspect of the present invention, a series resonance circuit including a resonance capacitor and a resonance reactor is used as the energy storage element. A zero voltage vector is output to an inverter to reduce the power ripple. Absorb by circuit.

According to a third aspect of the present invention, as the energy storage element, a ripple absorber connected between the neutral point of the star-connected stator winding of the motor and one of the AC input terminals of the converter. A power reactor is used, and a zero voltage vector is output to an inverter, and power ripple is absorbed by this reactor.

In any one of the first to third aspects of the present invention, as described in the fourth aspect, a reactor is inserted between a neutral point of the electric motor and the energy storage element,
The stator core of the electric motor may be shared as the core of the reactor. Further, in any one of the inventions described in claims 1 to 3, as described in claim 5, an AC load having no neutral point is connected to the polyphase output side of the inverter instead of the motor, and By connecting the neutral point of the reactor star-connected to the multi-phase output side to one end of the energy storage element, the present invention can be applied to an AC load having no neutral point.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIG. 1 is a circuit diagram showing an embodiment of the invention described in claim 1. In the drawing, 100 is a single-phase AC power supply, 200 is a self-arc-extinguishing semiconductor switching element such as an IGBT and a converter in which a single-phase full bridge is formed by an anti-parallel diode, and 300 is a similar self-extinguishing semiconductor switching element. A three-phase voltage source inverter comprising Tr1 to Tr6 and an anti-parallel diode;
02 is a smoothing capacitor provided in the DC intermediate circuit;
0 is a three-phase induction motor. Reference numeral 201 denotes a reactor for absorbing a ripple accompanying the switching of the converter 200. Further, in this embodiment, a ripple absorbing capacitor 601 as an energy storage element is connected between a neutral point of the stator winding of the electric motor 500 and a connection point between the lower arm of the inverter 300 and the smoothing capacitor 402. Have been.

In this embodiment, a three-phase voltage source inverter 30
It focuses on the zero voltage vector of 0. That is,
In the three-phase voltage source inverter 300, there are two types of switching patterns for outputting a zero voltage vector: a case where all the upper arms are made conductive and a case where all the lower arms are made conductive. In the present embodiment, this degree of freedom is used. .
Since the zero-phase voltage output from the inverter 300 does not appear in the line voltage, it does not affect the motor drive. Therefore,
The equivalent circuit for the positive phase of the output unit is as shown in FIG.
Regarding the driving of 00, the inverter operates as the same inverter as the conventional one, and exchanges AC power with the electric motor 500 by controlling the power by the line voltage of the inverter 300 and the current flowing between the lines.

On the other hand, when considering the zero-phase component, it becomes as shown in FIG. 3, and the three arms of the inverter 300 in FIG. 2 can be regarded as one arm 300 'that performs switching operation at a ratio of zero voltage vectors. Further, the electric motor 500 has a reactor 50 having a value of leakage inductance.
It can be considered as 1. The voltage of the capacitor 601 for absorbing power ripple becomes a zero-phase voltage when viewed from the AC output side of the inverter 300, and the electric motor 500 (reactor 50
By transferring zero-phase power between the inverter 300 and the capacitor 601 via 1), the one-arm (two-quadrant chopper 40) added in the prior art shown in FIG.
1) and the same operation as the reactor 403 and the capacitor 404 can be performed. Therefore, the capacity of the smoothing capacitor 402 can be reduced without the additional arm.

As described above, by transmitting and receiving the zero-phase power between the inverter 300 and the capacitor 601 by the circuit shown in FIG. 1, a single-phase to multi-phase power conversion circuit circuit substantially equivalent to FIG. 10 is realized. Therefore, it is possible to simplify the circuit configuration, reduce the size, and reduce the cost by reducing the number of additional arms and reactors. Note that the AC motor as a load may be a polyphase AC motor other than the three-phase induction motor.

The single-phase full-bridge converter shown in FIG.
200 indicates that the input current waveform is a sine wave in a well-known manner.
To work. Also, the three-phase voltage source inverter 300
PWM control is performed, and the PWM pulse is, for example, as shown in FIG.
It is created by the control circuit shown. In FIG.
Current finger flowing through capacitor 601 to absorb ripples
Or the zero-phase current command i₀ ^*The method of creating
"715 published in the proceedings of the 1996 IEEJ National Convention.
 Single-phase PWM controller with DC active filter function
It can be easily inferred from the
You. This zero-phase current command i₀ ^*By the multiplier 704
3 is a current finger for driving the electric motor 500.
Order i_a ^*, i_b ^*, i_c ^*To each phase current command i_u ^*, i_v ^*, i
_w ^*Create These and the actual detected current values of each phase i_u, i_v,
i_wAnd input to the current controllers 701 to 703
Then, the output is triangulated by comparators 705 to 707.
And compares each phase current with command i_u ^*, i_v ^*, i_w ^*Follow
Switching elements Tr1 to Tr3 of the inverter 300
Obtain a PWM pattern for Tr6.

That is, in this embodiment, by controlling the inverter 300 in a time division manner by the PWM pulse, the three-phase voltage source inverter of FIG.
The operation of superimposing the quadrant chopper 401 is performed. The former controls the line voltage and the current flowing between the lines by the positive-phase current, and the latter controls the input current of the capacitor 601 by the zero-phase current.

FIG. 5 shows another example of the control circuit. Current command of the motor 500 in the example of FIG. _{^{4 i a *, i b *}} , i
_The PWM pulse was obtained from _c ^* , but as shown in FIG.
Voltage is applied to the 00 command v _a ^*, v _b ^*, it is also possible to determine the PWM pulses from v _c ^*. In this case, a deviation between the zero-phase current command i ₀ ^* and the zero-phase current i ₀ obtained from each phase current is input to the current controller 708 to obtain a zero-phase voltage command v ₀ ^* , which is then referred to as a voltage command v _a ^*, v _b ^*, v the result of adding the _c ^* compared with the triangular wave by the comparator 705 to 707, PW to the switching element Tr1~Tr6 inverter 300
Obtain the M pattern.

The ripple of the input current of the capacitor 601 due to the switching of the inverter 300 is smoothed by the leakage inductance of the electric motor 500 (reactor 501 in FIG. 3). A reactor sharing the stator core of the electric motor 500 may be further connected between the neutral point of the stator winding of the electric motor 500 and the capacitor 601.

In the above embodiment, the power ripple absorbing capacitor 601 may be connected between the neutral point of the motor 500 and the connection point between the upper arm of the inverter 300 and the smoothing capacitor 402.

FIG. 6 is a circuit diagram showing an embodiment according to the second aspect of the present invention. In this embodiment, a series resonance circuit as an energy storage element including a resonance reactor 603 and a resonance capacitor 602 is provided between a neutral point of the electric motor 500 and a connection point between the lower arm of the inverter 300 and the smoothing capacitor 402. Is connected. If the iron core of the resonance reactor 603 is shared with and integrated with the stator iron core of the electric motor 500, the size of the apparatus can be further reduced. Other configurations are the same as the embodiment of FIG. Here, the resonance frequency of the series resonance circuit is selected to be twice the power supply frequency.

In this embodiment, similarly to the above, the single-phase full-bridge converter 200 operates so that the input current waveform becomes a sine wave. Further, PWM pulses for the switching elements Tr1 to Tr6 of the inverter 300 are obtained by the control circuit of FIG. That is, as shown in FIG. 7, in the present embodiment, the zero-phase voltage command v ₀ ^* is directly applied, and control is performed so that the zero-phase voltage v ₀ detected from each phase voltage is kept constant. 709 is a zero-phase voltage command v ₀ ^* and a zero-phase voltage detection value v
₀ is a voltage controller deviation is input with its output a voltage command ^{_{v a *, v b *,}} v the result of adding the _c ^* compared with the triangular wave by the comparator 705 to 707, inverter 3
00 for the switching elements Tr1 to Tr6
Get the pattern.

[0022] As a result, although the prior art of FIG. 11 was required withstand voltage of the resonant capacitor is more than twice the DC intermediate voltage, in the present embodiment, the magnitude of the zero-phase voltage command v ₀ ^* eg DC If the voltage is controlled to の of the intermediate voltage, the withstand voltage of the resonance capacitor 602 can be reduced to about の of that of the prior art, and the size and the price can be reduced. As is clear, in this embodiment, the resonance reactor 60 is used.
A series resonance circuit composed of the capacitor 3 and the resonance capacitor 602 functions as the LC filter 405 in FIG. 11, and absorbs power ripple having a frequency twice the power supply frequency. The principle of transmitting and receiving the zero-phase power between the inverter 300 and the series resonance circuit is the same as that of the embodiment of FIG.

In the above embodiment, the series resonance circuit including the resonance reactor 603 and the resonance capacitor 602 is connected between the neutral point of the motor 500 and the connection point between the upper arm of the inverter 300 and the smoothing capacitor 402. You may.

FIG. 8 shows a third embodiment of the present invention. In this embodiment, the electric motor 50
A ripple absorbing reactor 604 as an energy storage element is connected between a neutral point of zero and one AC input terminal of the converter 200 (the middle point of one of the upper and lower arms). The reactor 604 also shares the same iron core as the electric motor 500, and can be downsized by being integrated. In other configurations, the same components as those in the above embodiments are denoted by the same reference numerals.

As a control method of the present embodiment, the single-phase full-bridge converter 200 is operated so that the input current waveform becomes a sine wave as described above. In addition, the inverter 300
The PWM pulses for the switching elements Tr1 to Tr6 can be obtained by the control circuit of FIG. A method of creating the zero-phase voltage command v ₀ ^* for reducing the capacity of the smoothing capacitor 402 is described in “79 Reduction of DC Power Pulsation of Single-Phase Voltage Source PWM Converter” It can be easily inferred from the "method". The principle of transmitting and receiving the zero-phase power between the inverter 300 and the reactor 604 is the same as that of the embodiment of FIG. 1, and by controlling the current of the reactor 604 by outputting the zero voltage vector to the inverter 300, the arm in FIG. The same operation as 401 can be performed. Therefore,
The circuit in FIG. 8 is substantially equivalent to the circuit in FIG. 12, and the size and cost of the device can be reduced by reducing the number of additional arms.

In this embodiment, one end of the reactor 604 for absorbing power ripple may be connected to the other AC input terminal of the converter 200 (the middle point of the other upper and lower arms).

FIG. 9 is a circuit diagram showing an embodiment of the invention described in claim 5. This embodiment is based on the embodiment of FIG. 1 and connects the neutral point of the reactor 605 star-connected to each phase output terminal of the inverter 300 to one end of the capacitor 601 instead of the neutral point of the electric motor 500. It was done. According to this embodiment, the present invention can be applied to an AC load 502 having no neutral point.
The additional arm can be omitted and the capacity of the smoothing capacitor 402 can be reduced as in the embodiment of FIG. The overall operation and the control method of the inverter 300 are the same as those in the embodiment of FIG. The present embodiment is different from the embodiments shown in FIGS.
It is also applicable to a configuration in which 0 is removed.

In each of the above embodiments, the converter 20
Although a case where a single-phase full-bridge converter is used as 0 has been described, since the gist of the present invention is merely to reduce the capacity of the smoothing capacitor 402, the present invention can be applied to a case where a single-phase mixed-bridge converter or the like is used as the converter. It is.

[0029]

As described above, according to the first to third aspects of the present invention, the conventional additional arm can be reduced by controlling the zero-phase power by using the zero voltage vector of the inverter, and the circuit configuration is simplified. Thus, the capacity of the smoothing capacitor can be reduced while reducing the size and cost of the device. Further, a reactor conventionally provided for absorbing power ripples can be substituted by the leakage inductance of the electric motor, which also has a great effect in this respect.

According to the fourth and fifth aspects of the present invention,
Effective utilization of the stator iron core of the motor and application to an AC load having no neutral point are possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the invention described in claim 1;

FIG. 2 is a positive-phase equivalent circuit of an output unit in the embodiment of FIG. 1;

FIG. 3 is an equivalent circuit of a zero phase component of an output unit in the embodiment of FIG. 1;

FIG. 4 is a control circuit diagram of the embodiment of FIG.

FIG. 5 is a control circuit diagram of the embodiment of FIG. 1;

FIG. 6 is a circuit diagram showing an embodiment of the invention described in claim 2;

FIG. 7 is a control circuit diagram of the embodiment of FIG.

FIG. 8 is a circuit diagram showing an embodiment of the invention described in claim 3;

FIG. 9 is a circuit diagram showing an embodiment of the invention described in claim 5;

FIG. 10 is a circuit diagram showing a conventional technique.

FIG. 11 is a circuit diagram showing a conventional technique.

FIG. 12 is a circuit diagram showing a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 single-phase AC power supply 200 single-phase full-bridge converter 300 three-phase voltage source inverter 300 ′ arm 402 smoothing capacitor 500 three-phase induction motor 502 AC load 601, 602 capacitor 201, 501, 603 to 605 reactor 701 to 703 708 current control 704 Multiplier 705-707 Comparator 709 Voltage controller Tr1-Tr6 Self-extinguishing type semiconductor switching element

Claims (5)

[Claims] 1. A converter for converting a single-phase AC voltage to a DC voltage, a voltage-type inverter for converting the DC voltage to a polyphase AC voltage to drive a polyphase AC motor, and a smoothing circuit connected to a DC intermediate circuit. In a single-phase to multi-phase power conversion circuit having a capacitor, an energy storage element as an energy storage element is provided between a neutral point of a star-connected stator winding of a motor and one of connection points between an inverter and a smoothing capacitor. In addition to connecting the ripple absorbing capacitor, the inverter transfers power to and from the motor by time division, and transfers zero-phase power to and from the ripple absorbing capacitor when the inverter outputs a zero voltage vector. By controlling the DC voltage of the ripple absorbing capacitor, the power ripple of the DC intermediate circuit is absorbed by the ripple absorbing capacitor. Phase - multiphase power conversion circuit. 2. A converter for converting a single-phase AC voltage to a DC voltage, a voltage-type inverter for converting the DC voltage to a polyphase AC voltage to drive a polyphase AC motor, and a smoothing circuit connected to a DC intermediate circuit. A single-phase to multi-phase power conversion circuit having a capacitor, wherein an energy storage element is provided between a neutral point of the star-connected stator winding of the motor and one of connection points between the inverter and the smoothing capacitor. In addition to connecting a series resonance circuit consisting of a resonance capacitor and a resonance reactor, the inverter transmits and receives power to and from the motor by time division, and connects with the series resonance circuit when the inverter outputs a zero voltage vector. The power ripple of the DC intermediate circuit is absorbed by the series resonance circuit by controlling the voltage of the series resonance circuit by exchanging zero-phase power between the series resonance circuits. Single Phase - multiphase power conversion circuit. 3. A converter for converting a single-phase AC voltage to a DC voltage, a voltage-type inverter for converting the DC voltage to a polyphase AC voltage to drive a polyphase AC motor, and a smoothing circuit connected to a DC intermediate circuit. A single-phase to multi-phase power conversion circuit having a capacitor, for absorbing ripple as an energy storage element between a neutral point of a star-connected stator winding of an electric motor and one of an AC input terminal of a converter. In addition to connecting the reactor, the inverter exchanges power with the motor by time division, and also exchanges zero-phase power with the ripple absorption reactor when the inverter outputs a zero-voltage vector, thereby absorbing ripple. Single-phase to multi-phase power converter characterized in that the power ripple of the DC intermediate circuit is absorbed by the ripple absorbing reactor by controlling the current of the power reactor. Circuit. 4. The single-phase / multi-phase power conversion circuit according to claim 1, wherein a reactor is inserted between a neutral point of the motor and an energy storage element, and the reactor is used as an iron core of the reactor. A single-phase to multi-phase power conversion circuit using a stator iron core. 5. The single-phase to multi-phase power conversion circuit according to claim 1, wherein an AC load having no neutral point is connected to the multi-phase output side of the inverter in place of the motor, and A single-phase to multi-phase power conversion circuit, wherein a neutral point of a reactor star-connected to the multi-phase output side is connected to one end of an energy storage element.