JP3365254B2 - Single-phase to multi-phase power conversion circuit - Google Patents

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 which converts a single-phase AC power into a DC power by a converter and converts the DC power into a multi-phase AC power by a voltage source inverter to drive a multi-phase 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 "Reducing the Capacitance of Single-Phase PWM Converter with 715 DC Active Filter Function" published in the 1996 Annual Meeting of the Japan Institute of Electrical Engineers.
It is a conventional technique of a single-phase to multi-phase power conversion circuit using the circuit configuration described in (1). In the figure, 100 is a single-phase AC power supply,
Reference numeral 200 is a single-phase full-bridge converter that is PWM-controlled and consists of a self-extinguishing type semiconductor switching element such as an IGBT and an anti-parallel diode, and 300 is a three-phase voltage-type inverter including a similar self-extinguishing type semiconductor switching element and anti-parallel diode , 401 is a two-quadrant chopper, 402
Is a smoothing capacitor provided in the DC intermediate circuit, 403,
Reference numeral 404 denotes a filter reactor and capacitor, and 500 denotes a three-phase induction motor as a load. Although a detailed operation description of this circuit is omitted, the basic operation is to maintain the AC input current waveform in a sine wave by the PWM control of the converter 200 and control the input power factor to 1, while
2 of the power supply frequency generated on the DC output side of the converter 200
In order to absorb the power ripple having the double frequency, the voltage of the capacitor 404 is controlled by the two-quadrant chopper 401 to transfer energy, thereby reducing the capacity of the smoothing capacitor 402.

FIG. 11 is a paper published in 1993, The Institute of Electrical Engineers of Japan, Journal of Industrial Applications (vol.113-D, No.9, p.1106 to p.1107) entitled "DC Voltage Ripple of Single-Phase PWM Converter". FIG. 12 shows a conventional technique of a single-phase to multi-phase power conversion circuit using a circuit configuration described in "One Suppression Measure". Is a prior art of a single-phase to multi-phase power conversion circuit using the circuit configuration described in "DC power ripple reduction method of PWM converter". In these figures, 405 in FIG. 11 is an LC filter as a series resonance circuit connected to the DC intermediate circuit,
Reference numeral 406 in FIG. 12 is a reactor, and other components that are the same as those in FIG. 10 are denoted by the same reference numerals. Although detailed operation description of these circuits is omitted, basically,
2 of the power supply frequency generated on the DC output side of the converter 200
Double power ripple with the same resonance frequency
It is absorbed by the LC filter 405 of No. 1 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, the reactor is used for absorbing the power ripple, which hinders the miniaturization. Further, in the conventional techniques of FIGS. 10 and 12, it is necessary to add one upper and lower arm to the DC intermediate circuit, which is an obstacle to downsizing and cost reduction. Further, in the conventional technique of FIG. 11, the LC filter 4 is used.
There is a problem that the withstand voltage of the capacitor No. 05 is twice as high as the DC intermediate voltage.

In view of the above, the present invention solves the problems of each of the above-mentioned prior arts, downsizes the device with a simple circuit configuration, reduces the cost, and reduces the capacity of the 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 is a converter for converting a single-phase AC voltage into a DC voltage, and a converter for converting the DC voltage into a multi-phase AC voltage. In a single-phase to multi-phase power conversion circuit having a voltage source inverter for driving a phase alternating current motor and a smoothing capacitor connected to a direct current intermediate circuit, a neutral point of a stator winding of the electric motor, A ripple absorbing capacitor as an energy storage element is connected between the inverter and one of the connection points of the smoothing capacitor, and the inverter transmits and receives power to and from the electric motor by time division, and the zero by the inverter is obtained. When the voltage vector is output, the zero-phase power is exchanged with the ripple absorbing capacitor to control the DC voltage of the ripple absorbing capacitor. The pull is to absorbed by the ripple absorbing capacitors.

In the above structure, AC power is exchanged between the inverter and the electric motor in the same manner as in the conventional case by controlling the electric power by 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 by using the zero voltage vector of the inverter, it is possible to perform the same operation as the upper and lower one arm added to the DC intermediate circuit in the conventional technique, and thereby, the inverter. The zero-phase power is transferred 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, it is possible to reduce the number of additional arms in the related art, and it is possible to substitute the conventional power ripple absorbing reactor by the leakage reactance of the AC motor, which contributes to downsizing and cost reduction of the device.

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

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

In any one of the first to third aspects of the invention, as described in the fourth aspect, a reactor is inserted between the neutral point of the electric motor and the energy storage element,
The stator iron core of the electric motor may be shared as the iron core of this 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 multiphase output side of the inverter in place of the electric motor, and By connecting the neutral point of the reactor star-connected to the polyphase 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]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments 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 figure, similarly to the above, 100 is a single-phase AC power supply, 200 is a converter in which a single-phase full bridge is configured by a self-extinguishing semiconductor switching element such as an IGBT and an antiparallel diode, and 300 is a similar self-extinguishing semiconductor switching element. Three-phase voltage source inverter composed of Tr1 to Tr6 and anti-parallel diode, 4
02 is a smoothing capacitor provided in the DC intermediate circuit, 50
0 is a three-phase induction motor. Incidentally, 201 is a reactor for absorbing ripples accompanying switching of the converter 200. Further, in the present embodiment, the ripple absorbing capacitor 601 as an energy storage element is connected between the neutral point of the stator winding of the electric motor 500 and the connection point of the lower arm of the inverter 300 and the smoothing capacitor 402. Has been done.

This embodiment is a three-phase voltage source inverter 30.
The focus is on the zero voltage vector of zero. That is,
In order to output a zero voltage vector in the three-phase voltage source inverter 300, there are two switching patterns, that is, the case where all the upper arms are made conductive and the case where all the lower arms are made conductive, and this embodiment utilizes this degree of freedom. .
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 positive phase equivalent circuit of the output section is as shown in Fig. 2.
Regarding the driving of 00, it operates as the same inverter as the conventional one, and AC power is exchanged with the electric motor 500 by controlling the electric power by the line voltage of the inverter 300 and the current flowing between the lines.

On the other hand, 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 'which performs switching operation at the ratio of the zero voltage vector. Further, the electric motor 500 has a reactor 50 having a leakage inductance value.
It can be considered as 1. The voltage of the capacitor 601 for absorbing the 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 transmitting and receiving 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 of FIG. 10 is added.
1) and the reactor 403 and the capacitor 404. Therefore, the capacity of the smoothing capacitor 402 can be reduced without an additional arm.

As described above, by transmitting and receiving zero-phase power between the inverter 300 and the capacitor 601 by the circuit shown in FIG. 1, a single-phase / multi-phase power conversion circuit circuit substantially equivalent to that of FIG. 10 is realized. Therefore, the circuit configuration can be simplified, the size can be reduced, and the cost can be reduced by reducing the additional arm and the reactor. The AC motor as the load may be a multi-phase AC motor other than the three-phase induction motor.

Single-phase full-bridge converter in FIG.
In 200, the input current waveform becomes a sine wave by the well-known method.
Make it work. In addition, the three-phase voltage source inverter 300
PWM control is performed, and the PWM pulse is shown in FIG.
Created by the control circuit shown. In FIG. 4, electric power
A current finger that is passed through the capacitor 601 to absorb ripple
Order or zero-phase current command i₀ ^*The method of creating
The paper "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 reduction of the capacitor capacity of the burner
It This zero-phase current command i₀ ^*1 / by the multiplier 704
A value obtained by multiplying by 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 ^*To create. These and actual phase current detection values i_u, i_v,
i_wAnd the deviation is calculated and input to the current controllers 701 to 703.
Then, the output is triangulated by comparators 705 to 707.
Wave and compare each phase current with command i_u ^*, i_v ^*, i_w ^*To follow
Such as the switching element Tr1 of the inverter 300
Obtain the PWM pattern for Tr6.

That is, in this embodiment, the inverter 300 is time-divisionally controlled by the PWM pulse, so that the three-phase voltage source inverter shown in FIG.
The quadrant chopper 401 is overlapped with the former, and the former controls the line voltage by the positive phase current and the current flowing between the lines, 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. In the example of FIG. 4, the current commands i _a ^* , i _b ^* , i of the electric motor 500 are given.
_The PWM pulse was _calculated from _c ^* .
It is also possible to obtain the PWM pulse from the voltage commands v _a ^* , v _b ^* , v _c ^* applied to 00. In this case, the 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 the zero-phase voltage command v ₀ ^* , which is the voltage command v _a Comparing the result of addition to ^* , v _b ^* , v _c ^* with the triangular wave by comparators 705 to 707, PW for the switching elements Tr1 to Tr6 of the inverter 300 is performed.
Get 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), but if this is insufficient, it is described in claim 4. 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 electric motor 500 and the connection point between the upper arm of the inverter 300 and the smoothing capacitor 402.

Next, FIG. 6 is a circuit diagram showing an embodiment of the invention described in claim 2. In this embodiment, a series resonance circuit as an energy storage element including a resonance reactor 603 and a resonance capacitor 602 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. Are connected. If the iron core of the resonance reactor 603 is shared and integrated with the stator iron core of the electric motor 500, the size of the device can be further reduced. Other configurations are the same as those of 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 is operated so that the input current waveform becomes a sine wave. The PWM pulse for the switching elements Tr1 to Tr6 of the inverter 300 is 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 the zero-phase voltage v ₀ detected from each phase voltage is controlled to be kept constant. 709 is the zero-phase voltage command v ₀ ^* and the zero-phase voltage detection value v
_This is a voltage controller to which a deviation from ₀ is input, and the result of adding its output to the voltage commands v _a ^* , v _b ^* , v _c ^* is compared with the triangular wave by the comparators 705 to 707, and the inverter 3
PWM for switching elements Tr1 to Tr6 of 00
Get the pattern.

As a result, in the prior art of FIG. 11, the withstand voltage of the resonance capacitor needs to be at least twice as high as the DC intermediate voltage, but in the present embodiment, the magnitude is set to, for example, DC by the zero-phase voltage command v ₀ ^* . If the voltage is controlled to ½ of the intermediate voltage, the withstand voltage of the resonance capacitor 602 is about ½ of that of the conventional technique, and the size and cost can be reduced. As is apparent, in this embodiment, the resonance reactor 60 is used.
3 and the resonance capacitor 602 function as the LC filter 405 shown in FIG. 11, and absorb power ripple at a frequency twice the power supply frequency. The principle of transmitting / receiving zero-phase power between the inverter 300 and the series resonance circuit is the same as that of the embodiment shown in FIG.

In the above embodiment, the series resonance circuit composed of 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.

Next, FIG. 8 shows an embodiment of the invention described in claim 3. In this embodiment, the electric motor 50
A ripple absorbing reactor 604 as an energy storage element is connected between the neutral point of 0 and one of the AC input terminals of the converter 200 (the middle point of one of the upper and lower arms). This reactor 604 also shares the same iron core as the electric motor 500 and can be downsized by integrating them. The same components in the other configurations as those in the above-described embodiments are designated by the same reference numerals.

As the 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 pulse for the switching elements Tr1 to Tr6 can be obtained by the control circuit of FIG. For the method of creating the zero-phase voltage command v ₀ ^* for reducing the capacity of the smoothing capacitor 402, refer to a paper “79 Single-phase voltage source PWM converter DC power pulsation reduction” published in the 1996 IEEJ National Conference on Industrial Applications It can be easily inferred from "method". The principle of transmitting and receiving zero-phase power between the inverter 300 and the reactor 604 is similar to that of the embodiment of FIG. 1, and the arm in FIG. 12 is controlled by causing the inverter 300 to output a zero voltage vector and controlling the current of the reactor 604. The same operation as 401 can be performed. Therefore,
The circuit of FIG. 8 is substantially equivalent to the circuit of FIG. 12, and it is possible to reduce the size and cost of the device by reducing the number of additional arms.

In this embodiment, one end of the power ripple absorbing reactor 604 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 instead of the neutral point of the motor 500, the neutral point of the reactor 605 star-connected to each phase output terminal of the inverter 300 is connected to one end of the capacitor 601. It was done. According to this embodiment, it can be applied to the AC load 502 having no neutral point and the AC load 5
It is possible to omit the additional arm and to reduce the capacity of the smoothing capacitor 402 as in the embodiment of FIG. The overall operation and the control method of the inverter 300 are the same as in the embodiment of FIG. In this embodiment, the electric motor 50 is used in each of 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 the case where the single-phase full-bridge converter is used as 0 has been described, the point of the present invention is only to reduce the capacity of the smoothing capacitor 402, so that the present invention can be applied to the case where a single-phase mixed bridge converter or the like is used as the converter. Is.

[0029]

As described above, according to the inventions of claims 1 to 3, the conventional additional arms can be eliminated by controlling the zero-phase power by utilizing the zero voltage vector of the inverter, and the circuit configuration can be simplified. Therefore, the capacity of the smoothing capacitor can be reduced while reducing the size and cost of the device. Further, the reactor that has been conventionally provided for absorbing electric power ripples can be substituted by the leakage inductance of the electric motor, which is also a great effect.

According to the inventions of claims 4 and 5,
It is possible to effectively use the stator iron core of the electric motor and apply it to an AC load having no neutral point.

[Brief description of 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 the output section in the embodiment of FIG.

3 is a zero-phase equivalent circuit of the output section in the embodiment of FIG.

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

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

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]

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 and 602 capacitors 201,501,603-605 Reactor 701-703, 708 Current controller 704 multiplier 705-707 comparator 709 Voltage controller Tr1 to Tr6 Self-extinguishing type semiconductor switching element

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00 H02M 7/42-7/98 H02M 1 / 00-1/30

Claims (5)

(57) [Claims] 1. A converter for converting a single-phase AC voltage into a DC voltage, a voltage source inverter for converting the DC voltage into a multi-phase AC voltage to drive a multi-phase 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 between the neutral point of the star-connected stator winding of the motor and one of the connection points of the inverter and the smoothing capacitor By connecting a ripple absorption capacitor and time division, the inverter transfers power to and from the motor, and also transfers zero-phase power to the ripple absorption 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 into a DC voltage, a voltage source inverter for converting the DC voltage into a multi-phase AC voltage to drive a multi-phase 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, as an energy storage element between the neutral point of the star-shaped stator winding of the motor and one of the connection points of the inverter and the smoothing capacitor. The series resonance circuit consisting of the resonance capacitor and the resonance reactor is connected, and by time division, the inverter transfers power to and from the motor, and when the inverter outputs a zero voltage vector, the series resonance circuit Characterized in that 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 them. Single Phase - multiphase power conversion circuit. 3. A converter for converting a single-phase AC voltage into a DC voltage, a voltage source inverter for converting the DC voltage into a multi-phase AC voltage to drive a multi-phase AC motor, and a smoothing connected to a DC intermediate circuit. In a single-phase to multi-phase power conversion circuit having a capacitor, for absorbing ripple as an energy storage element between the neutral point of the stator winding of the motor and one of the AC input terminals of the converter. By connecting the reactor and time division, the inverter transfers power to and from the motor, and also transfers zero-phase power to and from the ripple absorbing reactor when the inverter outputs a zero voltage vector. 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, 2, or 3, wherein a reactor is inserted between a neutral point of the electric motor and an energy storage element, and the electric core of the electric motor 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, 2 or 3, wherein an AC load having no neutral point is connected to the multi-phase output side of the inverter instead of the electric motor, and A single-phase to multi-phase power conversion circuit, wherein a star-shaped reactor neutral point is connected to one end of an energy storage element on the multi-phase output side.