AC MOTOR DRIVE SYSTEM

• US 20160226423A1
• Filed: 10/02/2013
• Published: 08/04/2016
• Est. Priority Date: 10/02/2013
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: TABUCHI, Akiko, OKUDA, Tetsuya, KANDA, Yoshinori, WATABU, Kazuyoshi
• Granted Patent: US 9,543,882 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence

Abstract

When regenerative power from an AC motor via an inverter exceeds a predetermined power threshold, a charging/discharging control unit, which outputs a control signal for controlling the inverter on the basis of a DC bus voltage value and a charging/discharging current value, causes a power storage device to be charged such that the DC bus voltage value becomes a voltage threshold corresponding to the power threshold and causes a charging current at a start time of charging to the power storage device to start from a charging current value that is based on a DC bus voltage value.

Claims

1. An AC motor drive system comprising:

a converter that supplies DC power;

an inverter that converts the DC power into AC power;

a DC bus that connects the converter and the inverter;

an AC motor driven by the AC power;

a DC-voltage-value detecting unit that detects a DC bus voltage value on an output side of the converter;

a power storage device that is charged with the DC power from the DC bus and discharges the charged DC power to the DC bus;

a charging/discharging circuit connected to the DC bus in parallel with the inverter and connected between the DC bus and the power storage device, the charging/discharging circuit causing the power storage device to be charged and discharge;

a charging/discharging-current-value detecting unit that detects a charging/discharging current value of the power storage device; and

a charging/discharging control unit that outputs a control signal for controlling the inverter on a basis of the DC bus voltage value and the charging/discharging current value, wherein

when regenerative power from the AC motor via the inverter exceeds a predetermined power threshold, the charging/discharging control unit causes the power storage device to be charged such that the DC bus voltage value becomes a voltage threshold corresponding to the power threshold and causes a charging current at a start time of charging to the power storage device to start from a charging current value that is based on a DC bus voltage value of the DC bus.

2. The AC motor drive system according to claim 1, wherein the charging current value at a start time of charging to the power storage device is based on an amount of change of the DC bus voltage value at a start time of charging.

5. The AC motor drive system according to claim 1, wherein

the charging/discharging control unit includes an integral control unit, a proportional integral control unit, or a proportional integral and differential control unit corresponding to the DC bus voltage value and the voltage threshold, and

at a start time of charging to the power storage device, the charging/discharging control unit sets an integral component in the integral control unit, the proportional integral control unit, or the proportional integral and differential control unit to a value corresponding to the DC bus voltage value at the start time of charging.

3. An AC motor drive system comprising:

a converter that converts an AC current into DC power;

an inverter that converts the DC power into AC power that is different from AC power input to the converter;

a DC bus that connects the converter and the inverter;

an AC motor driven by the AC power that is an output of the inverter;

a DC-voltage-value detecting unit that detects a DC bus voltage value on an output side of the converter;

a power storage device that is charged with the DC power from the DC bus and discharges the charged DC power to the DC bus;

a charging/discharging circuit connected to the DC bus in parallel with the inverter and connected between the DC bus and the power storage device, the charging/discharging circuit causing the power storage device to be charged and discharge;

a charging/discharging-current-value detecting unit that detects a charging/discharging current value of the power storage device;

an AC-voltage-value detecting unit that detects an AC voltage value on an input side of the converter; and

a charging/discharging control unit that outputs a control signal for controlling the inverter on a basis of the DC bus voltage value, the charging/discharging current value, and the AC voltage value, wherein

when regenerative power from the AC motor via the inverter exceeds a predetermined power threshold, the charging/discharging control unit causes the power storage device to be charged such that the DC bus voltage value becomes a voltage threshold corresponding to the power threshold and the AC voltage value and causes a charging current at a start time of charging to the power storage device to start from a charging current value that is based on the DC bus voltage value and the AC voltage value.

4. The AC motor drive system according to claim 3, wherein the charging current value at a start time of charging to the power storage device is based on an amount of change of the DC bus voltage value at a start time of charging and based on the AC voltage value.

6. The AC motor drive system according to claim 3, wherein

the charging/discharging control unit includes an integral control unit, a proportional integral control unit, or a proportional integral and differential control unit corresponding to the DC bus voltage value and the voltage threshold, and

at a start time of charging to the power storage device, the charging/discharging control unit sets an integral component in the integral control unit, the proportional integral control unit, or the proportional integral and differential control unit to a value corresponding to the DC bus voltage value at the start time of charging.