AC motor drive device

• US 8,653,783 B2
• Filed: 03/31/2011
• Issued: 02/18/2014
• Est. Priority Date: 03/31/2011
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Ohashi, Manabu, Nakamura, Kazuya
• Primary Examiner(s): Santana, Eduardo Colon
• Assistant Examiner(s): CARRASQUILLO, JORGE L
• Application Number:
  US13/978,813
• Publication Number:
  US 20130285582A1
• Time in Patent Office: 1,055 Days
• Field of Search: 318/684, 318/377, 318/801, 318/139, 318/268, 318/376, 318/400.3, 318/800, 318/811, 318/722, 318/12, 318/138, 318/105, 318/262, 318/375, 318/224, 318/381, 318/732, 318/823, 363/132, 363/17, 363/37, 363/39, 363/40, 363/41, 363/124, 363/126, 363/131, 363/139, 307/66, 307/43, 307/44, 307/45, 307/47, 307/50, 307/64, 307/72, 219/626, 219/622, 219/676, 320/116, 320/118, 320/137, 320/138, 310/195, 310/198
• US Class Current: 318/811
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H02P 2201/03 AC-DC converter stage controlled to provide a defined DC link voltage general aspects of plural converters in cascade H02M
• CPC Class Codes: H02P 2201/07 DC-DC step-up or step-down converter inserted between the power supply and the inverter supplying the motor, e.g. to control voltage source fluctuations, to vary the motor speed general aspects of plural converters in cascade H02M
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 3/18 for stopping or slowing an ac motor
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A circuit switching element is provided that switches a step-up/step-down bidirectional chopper circuit, arranged between a DC bus and a power storage element, to a first chopper circuit or to a second chopper circuit, whose step-up and step-down characteristics are in a complementary relation. The first and second chopper circuits are used together at a time of charge and discharge. Accordingly, an AC motor drive device having mounted therein a power storage system is obtained, in which the power storage system can perform charge and discharge to and from the power storage element, regardless of a bus voltage and can increase energy use efficiency.

Claims

1. An AC motor drive device comprising:

a DC bus connected to a DC power supply;

an inverter that converts DC power supplied from the DC bus to AC power required for driving an AC motor; and

a power storage system that is connected to the DC bus in parallel with the inverter for controlling DC power of the DC bus,

wherein the power storage system comprises;

a power storage element that can store DC power;

a step-up/step-down bidirectional chopper circuit that includes two switching elements in series and a choke coil whose one end is connected to a serially connected terminal of the two switching elements, and is arranged between the DC bus and the power storage element to perform a charge operation from the DC bus to the power storage element and a discharge operation from the power storage element to the DC bus; and

a control circuit that executes control so that an operation of the step-up/step-down bidirectional chopper circuit is switched to a first operation as a first chopper circuit in which a positive terminal of one of the switching elements is connected to a positive side of the DC bus and the other end of the choke coil is connected to a positive terminal of the power storage element, or to a second operation as a second chopper circuit in which the other end of the choke coil is connected to the positive terminal of the DC bus and the positive terminal of the one switching element is connected to the positive terminal of the power storage element,

wherein the control circuit compares a voltage of the DC bus with a voltage of the power storage element, and before and after a timing at which a result of the comparison is changed, switches and executes the first operation and the second operation in a predetermined order, thereby realizing the charge operation and the discharge operation, respectively.

2. The AC motor drive device according to claim 1,

wherein the power storage system further includes a circuit switching element that switches the configuration of the step-up/step-down bidirectional chopper circuit to the first chopper circuit or to the second chopper circuit, and

wherein the control circuit compares the voltage of the DC bus with the voltage of the power storage element, and before and after a timing at which the result of the comparison is changed, causes the circuit switching element to switch a corresponding circuit of the first chopper circuit and the second chopper circuit to constitute the first chopper circuit or the second chopper circuit, to operate the first chopper circuit and the second chopper circuit in a predetermined order, thereby realizing the charge operation and the discharge operation, respectively.

3. The AC motor drive device according to claim 2, wherein the control circuit compares the voltage of the DC bus with the voltage of the power storage element at a time of driving the AC motor, and when the voltage of the DC bus becomes higher than the voltage of the power storage element and a charge command is generated, causes the circuit switching element to constitute the first chopper circuit so as to perform the charge operation to the power storage element, while stepping down the voltage of the DC bus;

and near a timing at which the voltage of the power storage element rises and the magnitude relation with the voltage of the DC bus is changed, causes the circuit switching element to constitute the second chopper circuit so as to perform the charge operation to the power storage element, while stepping up the voltage of the DC bus.

4. The AC motor drive device according to claim 3, wherein in a case where the circuit switching element constitutes the second chopper circuit, when a discharge command is generated, the control circuit causes the constituted second chopper circuit to perform a discharge operation to the DC bus, while stepping down the voltage of the power storage element;

and near a timing at which the voltage of the power storage element drops and the magnitude relation with the voltage of the DC bus is changed, causes the circuit switching element to constitute the first chopper circuit so as to perform the discharge operation to the DC bus, while stepping up the voltage of the power storage element.

5. The AC motor drive device according to claim 2, wherein at a time of power-on of the device, when a charge command is generated, the control circuit compares the voltage of the DC bus with the voltage of the power storage element, and when the voltage of the DC bus is higher than the voltage of the power storage element, causes the circuit switching element to constitute the first chopper circuit so as to perform the charge operation to the power storage element, while stepping down the voltage of the DC bus;

and near a timing at which the voltage of the power storage element rises and the magnitude relation with the voltage of the DC bus is changed, causes the circuit switching element to constitute the second chopper circuit so as to perform the charge operation to the power storage element, while stepping up the voltage of the DC bus, until the voltage of the power storage element exceeds the voltage of the DC bus and reaches a preset initial charge voltage.

6. The AC motor drive device according to claim 2, wherein at a time of operation completion at which the device is powered off, when a discharge command is generated, the control circuit causes the circuit switching element to constitute the second chopper circuit so as to perform the discharge operation to the DC bus, while stepping down the voltage of the power storage element;

and near a timing at which the voltage of the power storage element drops and the magnitude relation with the voltage of the DC bus is changed, causes the circuit switching element to constitute the first chopper circuit so as to perform the discharge operation to the DC bus, while stepping up the voltage of the power storage element, until the voltage of the power storage element reaches a discharge limit voltage, which is preset to be equal to or lower than the voltage of the DC bus.

7. The AC motor drive device according to claim 2, wherein the circuit switching element further includes a configuration in which connection between the positive terminal of the power storage element and the step-up/step-down bidirectional chopper circuit is opened.

8. The AC motor drive device according to claim 7, wherein when the circuit switching element constitutes the first chopper circuit, and when an abnormal signal is input from inside or outside of the device, the control circuit causes the circuit switching element to open the connection between the positive terminal of the power storage element and the other end of the choke coil.

9. The AC motor drive device according to claim 7, wherein when the circuit switching element constitutes the second chopper circuit, and when an abnormal signal is input from inside or outside of the device, the control circuit causes the circuit switching element to open the connection between the positive terminal of the power storage element and the positive terminal of the one switching element.