JP2003134833A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter in which the number of zero-phase detectors and control systems for suppressing zero-phase circulation current can be decreased. SOLUTION: The power converter comprises a plurality of sets of power converting circuit each comprising converter circuits 4A and 4B for rectifying an AC power supply 2 into DC power being supplied to smoothing circuits 14A and 14B, and inverter circuits 6A and 6B for inverting the output from the smoothing circuits into AC power being supplied to a load 8, wherein the power converting circuits are connected in parallel. Each set of smoothing circuits 14A and 14B is configured independently and the control circuit 11A, 11B, 10A, 10B of at least one of the converter circuit and the inverter circuit constituting the plurality of sets of power converting circuit is provided with a control means for suppressing zero-phase current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter, and more particularly to a power converter which suppresses generation of zero-phase circulating current.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a conventional parallel type power converter provided with a means for suppressing a zero-phase circulating current, which is disclosed, for example, in Japanese Patent Laid-Open No. 5-260793.

As shown in the figure, the parallel type power conversion device has reactors 3A, 3 connected to a three-phase AC power source 2.
B, converters 4A and 4B connected to these reactors 3A and 3B, smoothing capacitor 5 that smoothes the output voltage of these converters 4A and 4B, inverters 6A and 6B connected to smoothing capacitor 5, and these inverters 6A and 6B. 7A, 7 connected to the output side of
It consists of B. Also, in the reactors 7A and 7B,
The AC motor 8 serving as a load is connected. That is, the power conversion device includes the reactors 3A and 3B and the converter 4
A, 4B, inverters 6A, 6B, and reactor 7
Although A and 7B are respectively connected in parallel, a smoothing capacitor 5 that smoothes the output voltage of the converters 4A and 4B.
Is shared.

Further, in the parallel type power converter, the current detector 10 is connected to each phase of the inverters 6A and 6B connected in parallel.
A microcomputer 12 for controlling A, 10B and the inverters 6A, 6B is provided. During parallel operation, the microcomputer 12 obtains the circulating current circulating between the inverters 6A and 6B from the detected value of the current of each phase, and the inverter 6 reduces the circulating current.
It controls the outputs of A and 6B. Similarly, on the side of the converters connected in parallel, the current detectors 9A and 9B for detecting the currents of the respective phases of the converters 4A and 4B and the converter 4 are also provided.
A microcomputer 11 for controlling A and 4B is provided,
The microcomputer obtains the circulating current circulating between the converters 4A and 4B from the detected value of the current of each phase, and the converters 4A and 4B are arranged to reduce the circulating current.
Control the output of B.

[0005]

In the conventional converter, the zero-phase currents flow in opposite directions on the inverter 6A side and the inverter 6B side. For example, the zero-phase current flowing out from the inverter 6A side to the electric motor 8 side flows into the inverter 6B side from the electric motor 8 side to the inverter 6B side. For this reason, when controlling two inverters (6A, 6B) with one microcomputer 12, for example, if the zero-phase current suppressing operation is performed in accordance with the inverter 6A, the zero-phase current is sufficiently suppressed on the inverter 6B side. There are times when you cannot do it. That is, the zero-phase circulating current cannot be effectively suppressed only by supplying the same control signal to the two inverters 6A and 6B by one microcomputer 12. The same applies to converters 4A and 4B.

Further, since the conventional power converter shares the smoothing capacitor 5 for smoothing the output voltage of the converters 4A and 4B, when the converters or the inverters are operated in parallel via the reactor as described above,
Circulating current, that is, zero-phase current, is generated between the inverters and between the converters. In order to suppress this circulating current, a zero-phase current detector for detecting the circulating current and a control means for suppressing the zero-phase current are required between the inverters and between the converters, respectively. There is a problem that a large number of phase current detectors are required and the control system becomes complicated.

The present invention has been made in view of these problems, and it is possible to prevent the interference between the means for suppressing the zero-phase current, and to further control the zero-phase current detector and the zero-phase circulating current. Provided is a power conversion device capable of reducing the number of systems.

[0008]

The present invention adopts the following means in order to solve the above problems.

A plurality of sets of power conversion circuits each including a converter circuit that rectifies an AC power supply and supplies it to a smoothing circuit and an inverter circuit that converts the output of the smoothing circuit into AC power and supplies the AC power to a load are provided. In a power conversion device in which the smoothing circuits of each set are configured independently of each other, and a control circuit for at least one circuit of a converter circuit and an inverter circuit that configures the plurality of sets of power conversion circuits. Has a control means for suppressing the zero-phase current.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a power conversion device according to an embodiment of the present invention. As shown in the figure, the power conversion device includes a parallel circuit including a first power conversion circuit 1A and a second power conversion circuit 1B.

The first power conversion circuit 1A includes a reactor 3
A, a converter 4A connected to the reactor 3A, a smoothing capacitor 5A for smoothing the output voltage of the converter 4A,
It is composed of an inverter 6A connected to the smoothing capacitor 5A and a reactor 7A connected to the output of the inverter 6A. Further, the second power conversion circuit 1B includes a reactor 3B, a converter 4B connected to the reactor 3B, and a converter 4B.
Smoothing capacitor 5B for smoothing the output voltage of the inverter, an inverter 6B connected to the smoothing capacitor 5B, an inverter 6B
It consists of a reactor 7B connected to the output of. A three-phase AC power supply 2 is connected to the reactors 3A and 3B, and an AC electric motor 8 as a load is connected to the reactors 7A and 7B. That is, the first and second power conversion circuits are independently provided with the smoothing capacitors 5A and 5B.

Further, on the converters 4A and 4B side,
Control devices 11A and 11B are provided to control converters 4A and 4B, respectively. Controllers 11A and 1
1B can be composed of, for example, a microcomputer.

The control devices 11A and 11B are converters.
Current I of each phase_u, I_v, I_wCurrent detector 9 for detecting
A, 9B, smoothing capacitor voltage E_dVoltage detection
Detection inputs of the generators 14A and 14B and operation control of the electric motor 8
Control command value E to control_d ^*, I_d ^*, I_z ^*Based on
Then, the converters 4A and 4B are PWM-controlled, for example.

Also, on the side of the inverters 6A and 6B,
Control devices 12A and 12B for controlling inverters 6A and 6B, respectively, are provided. Controllers 12A and 1
2B can be composed of, for example, a microcomputer.

The control devices 12A and 12B are current detectors 1 for detecting the currents I _u , I _v , and I _w of each phase of the inverter.
0A, 10B, speed detector 1 for detecting the speed ω of the electric motor
Inverter 6A based on the detection input of 3 and the control command values ω ^* , I _d ^* , I _z ^* for controlling the operation of electric motor 8;
6B is PWM-controlled, for example.

FIG. 2 is a single line connection diagram of the power converter shown in FIG. 1, showing a flow path of zero-phase current. As shown in FIG. 2, one zero-phase current I _z circulating between the inverters 6A and 6B and the converters 4A and 4B is generated via the reactors 3A, 3B, 7A and 7B. Therefore, this zero-phase circulating current I _z can be controlled (suppressed) by controlling any one of converters 4A, 4B and inverters 6A, 6B. That is, by providing the zero-phase current suppressing means in any one of the control devices 11A, 11B, 12A and 12B, the zero-phase current I
It is possible to suppress _z .

FIG. 3 is a diagram showing the details of the control devices (vector control devices) 12A, 12B for controlling the inverters.

The speed ω detected by the speed detector 13 shown in FIG. 1 is controlled by the speed controller 19 so as to match the speed command ω ^* , and the torque current command I _q ^* is calculated. Further, the detected values i _u , _iv , and i _w of the three-phase current are the coordinate converter 1
5, the torque current component I according to the following equation 1
_q , the exciting current component I _d , and the zero-phase current component I _z .

[0019]

[Equation 1] I_q, I_d, I_zEach converted value of is the torque current command
I_q ^*, Excitation current command I _d ^*, Zero-phase current command I_z ^*One
Torque current controller 16 and exciting current controller 1
7 and zero-phase current regulator 18. here
Then, the zero-phase current command I _z ^*For suppressing the zero-phase current
This is a command value and is normally 0. Also, the torque current regulator
16, exciting current controller 17, zero-phase current controller 18, and
And the speed controller 19 are general proportional-integral controllers (PI adjustment).
Vessel) etc. The output of each of these regulators is
Luke voltage command V_q ^*, Excitation voltage command V_d ^*, And zero phase
Voltage command V_z ^*Becomes

From the outputs V _q ^* , V _d ^* , V _z ^*, the three-phase voltage commands V _u ^* , V _u ^* are obtained by using the coordinate converters 20, 21.
V _v ^* and V _w ^* are obtained, and the inverter is controlled based on the obtained three-phase command voltage.

FIG. 4 is a diagram showing the details of the control devices (vector control devices) 11A and 11B for controlling the converter.

The voltage E _d detected by the voltage detectors 14A and 14B is controlled by the voltage regulator 26 so as to match the voltage command E _d ^* , and the active current command I _q ^* is calculated. Further, the detected values i _u , _iv , and i _w of the three-phase current are calculated by the coordinate converter 22 according to the equation 1 as the active current component I
_q , a reactive current component I _d , and a zero-phase current component I _z .

I_q, I_d, I_zEach conversion value of
Effective current command I_q ^*, Reactive current command I_d ^*, Zero-phase current command
I_z ^*Active current regulator 23, reactive current regulator
It is controlled by the node device 24 and the zero-phase current regulator 25. This
Here, the reactive current command is the command value for suppressing the reactive current.
And the zero-phase current command I_z ^*Suppresses the zero-phase current
Since it is a command value for each, it is usually set to 0. Also,
Active current controller 23, reactive current controller 24, zero-phase current regulator
The node 25 and the voltage regulator 26 are general proportional-integral regulators.
It may be a node (PI adjuster) or the like. The output of these regulators
Is the effective voltage command V_q ^*, Reactive voltage command
V_d ^*, Zero-phase voltage command V_z ^*Becomes

From the outputs V _q ^* , V _d ^* , V _z ^*, the three-phase voltage commands V _u ^* , V _u ^* are obtained by using the coordinate converters 27, 28.
V _v ^* and V _w ^* are obtained, and the converter is controlled based on the obtained three-phase voltage command.

As described above, according to this embodiment, any one of the control devices 11A, 11B, 12A and 12B for controlling the converter or the inverter is provided with the means for suppressing the zero-phase current. It is possible to suppress the zero-phase current I _z . At this time, the other control device may be provided with a general vector controller omitting the zero-phase current regulator 18 or 25, so that the cost can be reduced. Further, no interference occurs between the means for suppressing the zero-phase current. Further, in order to configure the power conversion device (FIG. 1) of this embodiment, a conventional power converter including a converter, a smoothing capacitor, and an inverter is used, for example, 2
Since it is only necessary to prepare a pair and connect these converters in parallel via the reactors 3A and 3B and the reactors 7A and 7B, it is possible to reduce the number of working steps and the manufacturing cost.

[0026]

As described above, according to the present invention, it is possible to prevent the interference between the means for suppressing the zero-phase current,
Further, it is possible to provide a power conversion device that can reduce the number of zero-phase current detectors and control systems that suppress zero-phase circulating current.

[Brief description of drawings]

FIG. 1 is a diagram showing a power conversion device according to an embodiment of the present invention.

FIG. 2 is a single line connection diagram of the power conversion device.

FIG. 3 is a diagram illustrating a control device that controls an inverter.

FIG. 4 is a diagram showing a control device for controlling the converter.

FIG. 5 is a diagram showing a conventional power conversion device.

[Explanation of symbols]

1A, 1B power conversion circuit 2-3 phase AC power supply 3A, 3B, 7A, 7B Reactor 4A, 4B converter 5A, 5B smoothing capacitor 6A, 6B inverter 8 3-phase induction motor 9A, 9B, 10A, 10B Current detector 11A, 11B, 12A, 12B control device 13 Speed detector 14 Voltage detector 15, 20, 21, 22, 22, 27, 28 Coordinate converter 16 Torque current regulator 17 Excitation current controller 18 Zero-phase current regulator 19 Speed regulator 23 Active Current Controller 24 Reactive current controller 25 Zero-phase current regulator 26 Voltage regulator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sadao Hokari             1070 Ichimo, Hitachinaka City, Ibaraki Prefecture Stock Association             Hitachi Systems Building Systems Group (72) Inventor Shunsuke Mine             1070 Ichimo, Hitachinaka City, Ibaraki Prefecture Stock Association             Hitachi Systems Building Systems Group (72) Inventor Toshifumi Yoshikawa             7-1-1, Omika-cho, Hitachi-shi, Ibaraki Prefecture             Inside the Hitachi Research Laboratory, Hitachi Ltd. F-term (reference) 5H006 BB05 CA01 CB01 CB08 CC04                       DA02 DB01 DC02 DC05                 5H007 BB06 CA01 CB05 CC05 DA05                       DB01 DC02

Claims (2)

[Claims] 1. A plurality of sets of power conversion circuits each including a converter circuit that rectifies an AC power supply and supplies it to a smoothing circuit, and an inverter circuit that converts the output of the smoothing circuit into AC power and supplies the AC power to a load. In a power conversion device in which conversion circuits are connected in parallel, each set of smoothing circuits is configured independently of each other, and at least one circuit of a converter circuit and an inverter circuit that configures the plurality of sets of power conversion circuits is provided. The power conversion device, wherein the control circuit includes control means for suppressing the zero-phase current. 2. The power converter according to claim 1, wherein the power converter includes a vector controller, and an electric motor is connected as the load.