Method and inverter with thermal management for controlling an electric machine

Patent metadata

Field	Value
Publication number	US-9698722-B2
Application number	US-201514837496-A
Country	US
Kind code	B2
Filing date	Aug 27, 2015
Priority date	Jun 19, 2015
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A temperature estimation module estimates each junction temperature of a corresponding semiconductor device, among a plurality of semiconductor devices, for each phase of an inverter. The temperature estimation module or the data processing system determines a hottest device with a highest junction temperature among the semiconductor devices. A thermal adjustment module or data processing system determines if the highest junction temperature parameter is less than maximum junction temperature parameter for the respective semiconductor device or deciding whether or not to adjust a duty cycle of the semiconductor devices.

First claim

The following is claimed:

1. A method for operating an inverter to control an electric machine, the method comprising:
determining a fundamental frequency of one or more inverter phases based on a torque command to control the torque, speed or direction of the electric machine;
establishing an initial reference output current based on the torque command;
estimating each junction temperature of a corresponding semiconductor device, among a plurality of semiconductor devices, for each phase of an inverter;
determining a hottest device with a highest junction temperature among the semiconductor devices in the inverter; and
determining if the highest junction temperature parameter is less than maximum junction temperature parameter for the respective semiconductor device for deciding whether or not to adjust a duty cycle of the semiconductor devices.

2. The method according to claim 1 further comprising:
adjusting the duty cycle if the fundamental frequency is less than the threshold frequency and if the highest junction temperature is greater than or equal to the maximum junction temperature parameter.

3. The method according to claim 1 further comprising:
determining whether the duty cycle adjustment is at a maximum; and
adjusting the duty cycle if the duty cycle adjustment is not at the maximum, to limit the junction temperature of the hottest device at an output current level, and if the estimated junction temperature parameter is greater than or equal to the maximum junction temperature parameter.

4. The method according to claim 1 further comprising:
authorize availability of an increase in the initial reference output current if the junction temperature is less than the maximum junction temperature, the availability of the increase dependent upon the torque command.

5. The method according to claim 1 further comprising:
determining whether the duty cycle adjustment is at a maximum or limit; and
adjusting the duty cycle upward if the duty cycle adjustment is not at the maximum or limit to limit the junction temperature if the hottest device among the semiconductor devices is a not a high-side switch or not a high-side diode.

6. The method according to claim 5 wherein the duty cycle is determined based on a maximum current in one of the semiconductor devices or an output phase with a highest current, a medium current in a semiconductor device or an output phase with a lower current than the maximum current but not the minimum current device or phase, and a peak adjusted duty cycle, wherein the peak adjusted duty cycle stored in a data storage device and can be determined by a characterization of the inverter.

7. The method according to claim 5 wherein the duty cycle is adjusted in accordance with the following equation:


AdjustedDuty


=

3
×



I
max



-



I
medium





I
max



+



I
medium



×
PeakAdjustedDuty

where “PeakAdjustedDuty” is the desired peak adjusted duty cycle data, I max is the maximum current of a semiconductor device with a greatest current, and I medium is the medium current of another semiconductor device of a different phase that is less than the maximum current.

8. The method according to claim 1 further comprising:
determining whether the duty cycle adjustment is at a maximum; and
adjusting the duty cycle downward if the duty cycle adjustment is not at the maximum to limit the junction temperature if the hottest device among the semiconductor devices is a high-side switch or a high-side diode.

9. The method according to claim 8 wherein the duty cycle is determined based on a maximum current, a medium current, and a peak adjusted duty parameter, wherein the peak adjusted parameter stored in data storage device and can be determined by a characterization of the inverter.

10. The method according to claim 8 wherein the duty cycle is adjusted in accordance with the following equation:


AdjustedDuty


=

3
×



I
max



-



I
medium





I
max



+



I
medium



×
PeakAdjustedDuty

where “PeakAdjustedDuty” is the desired peak adjusted duty cycle data, I max is the maximum current of a semiconductor device with a greatest current, and I medium is the medium current of another semiconductor device of a different phase that is less than the maximum current.

11. A method for operating an inverter to control an electric machine, the method comprising:
determining a fundamental frequency of one or more inverter phases based on a torque command to control the torque, speed or direction of the electric machine;
estimating each junction temperature of a corresponding semiconductor device, among a plurality of semiconductor devices, for each phase of an inverter based on a characterization of a dynamic thermal impedance and power dissipation for each one of the semiconductor devices;
determining a hottest device with a highest junction temperature among the semiconductor devices; and
establishing a thermal allocation among semiconductor devices, the semiconductor devices comprising a low-side semiconductor switch, a high-side semiconductor switch, a low-side diode and a high-side diode, to limit a junction temperature of the hottest device among the semiconductor devices to a maximum temperature by shifting heat dissipation to one or more semiconductor devices with

Assignees

• Deere & Co

Inventors

• Loken David M
• Wu Long
• Fu Tianjun
• Shaw Robert B
• Clements Neal D

Classifications

• H02P29/68 Primary

  based on the temperature of a drive component or a semiconductor component · CPC title

• H02P29/0088 Primary

  Electricity · mapped topic

• H02M7/53875

  with analogue control of three-phase output · CPC title

• H02M1/327

  against abnormal temperatures · CPC title

• H02P2201/00

  Indexing scheme relating to controlling arrangements characterised by the converter used · CPC title