Power conversion apparatus

Patent metadata

Field	Value
Publication number	US-9287698-B2
Application number	US-201113993604-A
Country	US
Kind code	B2
Filing date	Dec 21, 2011
Priority date	Dec 22, 2010
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

A controller for switching an inverter includes a current detecting unit, an overcurrent level determining unit which determines an overcurrent level for stopping the inverter in accordance with a value corresponding to the number of revolutions of a motor, a current comparing unit which compares a detected output current value of the inverter with the overcurrent level, and a gate signal generating unit which generates a signal for turning off all semiconductor switching devices of the inverter when the current comparing unit makes a determination that the detected output current value has reached the overcurrent level. The overcurrent level is lowered as the number of revolutions of the motor increases.

First claim

The invention claimed is:

1. A power conversion apparatus for driving an AC motor by using an inverter having a DC side to which a parallel circuit having a DC power supply and a capacitor is connected, wherein a controller for controlling semiconductor switching devices of the inverter includes:
a current detecting unit which detects an output current of the inverter;
an overcurrent level determining unit which determines an overcurrent level for stopping operation of the inverter in accordance with a value corresponding to a number of revolutions of the motor;
a current comparing unit which compares a detected output current value of the inverter outputted from the current detecting unit with the overcurrent level determined by the overcurrent level determining unit; and
a drive signal generating unit which generates a signal for turning off all the semiconductor switching devices of the inverter when the current comparing unit makes a determination that the detected output current value has reached the overcurrent level;
wherein:
the overcurrent level determined by the overcurrent level determining unit becomes lower in terms of value as the value corresponding to the number of revolutions becomes larger in a constant output region of the motor.

2. The power conversion apparatus of claim 1 , wherein:
the value corresponding to the number of revolutions of the motor is any one of a detected value of the number of revolutions, an estimated value of the number of revolutions or a commanded value of the number of revolutions.

3. The power conversion apparatus of claim 1 , wherein:
the value corresponding to the number of revolutions of the motor is any one of a detected value of the number of revolutions, an estimated value of the number of revolutions or a commanded value of the number of revolutions.

4. The power conversion apparatus of claim 1 , wherein:
the inverter and the motor form a vehicle drive system for a hybrid automobile or an electric automobile.

5. The power conversion apparatus of claim 1 , wherein:
the inverter and the motor form a vehicle drive system for a hybrid automobile or an electric automobile.

6. The power conversion apparatus of claim 1 , wherein: the motor is a permanent magnet synchronous motor.

7. The power conversion apparatus of claim 1 , wherein:
the motor is a permanent magnet synchronous motor.

8. A power conversion apparatus for driving an AC motor by using an inverter having a DC side to which a parallel circuit having a DC power supply and a capacitor is connected, wherein a controller for controlling semiconductor switching devices of the inverter includes:
a current detecting unit which detects an output current of the inverter;
an overcurrent level determining unit which determines an overcurrent level for stopping operation of the inverter in accordance with a value corresponding to a number of revolutions of the motor;
a current limit level determining unit which determines a current limit level for limiting the output current of the inverter in accordance with the value corresponding to the number of revolutions of the motor;
a current comparing unit which compares a detected output current value of the inverter outputted from the current detecting unit with the overcurrent level determined by the overcurrent level determining unit, and which compares the detected output current value with the current limit level determined by the current limit level determining unit; and
a drive signal generating unit which generates a signal for turning off all the semiconductor switching devices of the inverter when the current comparing unit makes a determination that the detected output current value has reached the overcurrent level, and which generates a signal for limiting the output current of the inverter at a certain phase when the current comparing unit makes a determination that the detected output current value has reached the current limit level;
wherein:
the overcurrent level determined by the overcurrent level determining unit and the current limit level determined by the current limit level determining unit become lower in terms of value as the value corresponding to the number of revolutions becomes larger in a constant output region of the motor.

9. The power conversion apparatus of claim 8 , wherein:
the current limit level is lower in terms of value than the overcurrent level in a whole range for the value corresponding to the number of revolutions of the motor.

10. The power conversion apparatus of claim 8 , wherein:
the drive signal generating unit generates a signal for stopping switching at a certain phase of the inverter when the detected output current value at the phase has reached the current limit level.

11. The power conversion apparatus of claim 8 , wherein:
the drive signal generating unit generates a signal for shortening a width of a pulse for turning on the semiconductor switching devices of the inverter at a certain phase when the detected output current value at the phase has reached the current limit level.

12. The power conversion apparatus of claim 8 , wherein:
the overcurrent level determined by the overcurrent level determining unit becomes lower in terms of value as the value corresponding to the number of revolutions becomes larger in a constant output region of the motor.

13. The power conversion apparatus of claim 8 , wherein:
the motor is a permanent magnet synchronous motor.

14. The power conversion apparatus of claim 8 , wherein the overcurrent level and the current limit level in accordance with the value corresponding to the number of revolutions of the motor are stored in advance as numerical data in a memory of the controller.

15. The power conversion apparatus of claim 14 , wherein the overcurrent level and the current limit level stored in advance as numerical data in the memory of the controller are defined as a plurality of values that decrease or increase in steps of a fixed size and correspond respectively to fixed ranges of the number of revolutions of the motor, and the steps decrease as the fixed ranges increase, or increase as the fixed ranges decrease.

16. An apparatus, comprising:
a current detecting device configured to detect a current; and
an overcurrent protection device configured to stop or inhibit an overcurrent condition based at least in part on the detected current and a motor speed;
wherein the overcurrent protection device is configured to lower a threshold for determining that an overcurrent has occurred in response to an increase in the motor speed; and
wherein the overcurrent protection device comprises:
a comparison device configured to compare the detected current to a current threshold and output a comparison signal; and
an overcurrent determination device configured to supply a range of current thresholds to the comparison device for comparison with the detected current;
wherein values in the range of current thresholds decrease with increasing values of the motor speed.

17. The apparatus of claim 16 , wherein the overcurrent protection device further comprises:
an overcurrent inhibiting device configured to stop or inhibit a current in response to the comparison signal indicating that an overcurrent has occurred.

18. The apparatus of claim 17 , wherein the motor includes a three-phase AC motor.

19. The apparatus of claim 18 , wherein the overcurrent inhibiting device is configured to stop or inhibit the current by turning off at least one switch of an inverter that drives the m

Assignees

• Oguchi Hideki
• Toba Akio
• Fuji Electric Co Ltd

Inventors

• Oguchi Hideki
• Toba Akio

Classifications

• H02P3/18

  for stopping or slowing an AC motor · CPC title

• B60L3/003 Primary

  relating to inverters · CPC title

• B60L50/62

  charged by low-power generators primarily intended to support the batteries, e.g. range extenders · CPC title

• B60L2240/529

  Current · CPC title

• H02P3/26

  by combined electrical and mechanical braking · CPC title