Operating an electrical machine

Patent metadata

Field	Value
Publication number	US-11211895-B2
Application number	US-201817043748-A
Country	US
Kind code	B2
Filing date	May 18, 2018
Priority date	May 18, 2018
Publication date	Dec 28, 2021
Grant date	Dec 28, 2021

Abstract

A method for operating an electrical machine is used to calculate a value of a first torque which can be provided at a maximum by the electrical machine in a future interval, wherein, by limiting the torque which is provided in the interval to the value, overheating of at least one semiconductor, which is required for transmitting the electrical power, due to a power loss is prevented and/or the threat of overheating and the onset of derating is diagnosed and therefore prevented.

First claim

The invention claimed is:

1. A method for the operation of an electric machine comprising:
a) ascertaining electrical parameters with which the electric machine is being operated at a current time point;
b) calculating a maximum second torque that can be generated by the electric machine at the electrical parameters;
c) calculating an electrical power loss that would arise at at least one semiconductor if the maximum second torque that can be generated is applied, wherein the at least one semiconductor is required for transmission of the electrical power resulting from a power loss;
d) calculating a resulting first temperature of a semiconductor junction layer of the at least one semiconductor that would result from the electrical power loss present during a future interval;
e) iteratively performing steps b) to d) with smaller values of the maximum second torque that can be generated according to step b) each iteration until the resulting first temperature that is calculated in accordance with step d) corresponds at most to a maximum permissible second temperature of the semiconductor junction layer; and
f) then one of operating the electric machine during the future interval with a torque whose value is at most the maximum second torque ascertained by step e) or operating the electric machine with a higher torque than the maximum second torque ascertained by step e) for an interval shorter than the future interval.

2. The method of claim 1 , wherein the electrical parameters in step a) comprise a current rotation speed of the electric machine and a current electrical voltage that is present for operation of the electric machine.

3. The method of claim 1 , wherein calculating the resulting first temperature in step d) is based at least on a cooling power that is available for cooling the at least one semiconductor.

4. The method of claim 1 , wherein a difference between the calculated resulting first temperature and the maximum permissible second temperature is formed in step e), and a difference torque is determined by a controller with reference to this difference, which is subtracted in the following iteration in step b) from the maximum second torque that can be generated of the preceding iteration in order to calculate a maximum second torque that can be generated for the immediately following steps c) to d).

5. The method of claim 4 , wherein the controller is one of an I-controller or a PI-controller.

6. The method of claim 1 , wherein the electric machine is operated with a multiphase alternating current of an inverter which has a switching frequency; wherein the parameters ascertained in step a) comprise at least an intermediate circuit voltage of the inverter as a current electrical voltage; the method further comprising, in a step b1) that follows step b), determining at least the following further electrical parameters: line current of each phase of the alternating current, line voltage of each phase of the alternating current, and power factor.

7. The method of claim 1 , wherein calculating the electrical power loss in step c) is based at least on properties of the electric machine and a control strategy of the electric machine.

8. The method of claim 1 , wherein the interval has a duration of at most 10 seconds.

9. The method of claim 1 , wherein the interval has a duration of at least 0.5 seconds.

10. The method of claim 1 , wherein the electric machine is a first drive unit of a motor vehicle; further comprising, when a requested torque for drive of the motor vehicle exceeds the value of the torque in the interval ascertained by the method in accordance with step f), switching on at least one second drive unit of the motor vehicle to increase the torque provided.

11. An electric drive arrangement comprising:
at least one electric machine;
an energy source;
at least one semiconductor, via which the electrical energy of the energy source can be supplied for operation of the electric machine; and
a control unit programmed to:
a) ascertain electrical parameters with which the electric machine is being operated at a current time point;
b) calculate a maximum second torque that can be generated by the electric machine at the electrical parameters;
c) calculate an electrical power loss that would arise at the at least one semiconductor if the maximum second torque that can be generated is applied;
d) calculate a resulting first temperature of a semiconductor junction layer of the at least one semiconductor that would result from the electrical power loss present during a future interval;
e) iteratively perform steps b) to d) with smaller values of the maximum second torque that can be generated according to step b) each iteration until the resulting first temperature that is calculated in accordance with step d) corresponds at most to a maximum permissible second temperature of the semiconductor junction layer; and
f) then one of operate the electric machine during the future interval with a torque whose value is at most the maximum second torque ascertained by step e) or operate the electric machine with a higher torque than the maximum second torque ascertained by step e) for an interval shorter than the future interval.

12. The electric drive arrangement of claim 11 , wherein the electric machine is configured to drive a motor vehicle.

13. The electric drive arrangement of claim 11 , wherein the electrical parameters in step a) comprise a current rotation speed of the electric machine and a current electrical voltage that is present for operation of the electric machine.

14. The electric drive arrangement of claim 11 , wherein calculating the resulting first temperature in step d) is based at least on a cooling power that is available for cooling the at least one semiconductor.

15. The electric drive arrangement of claim 11 , wherein a difference between the calculated resulting first temperature and the maximum permissible second temperature is formed in step e), and a difference torque is determined by a controller with reference to this difference, which is subtracted in the following iteration in step b) from the maximum second torque that can be generated of the preceding iteration in order to calculate a maximum second torque that can be generated for the immediately following steps c) to d).

16. The electric drive arrangement of claim 11 , wherein the electric machine is operated with a multiphase alternating current of an inverter which has a switching frequency; wherein the parameters ascertained in step a) comprise at least an intermediate circuit voltage of the inverter as a current electrical voltage; wherein the control unit is further programmed to, in a step b1) that follows step b), determine at least the following further electrical parameters: line current of each phase of the alternating current, line voltage of each phase of the alternating current, and power factor.

17. The electric drive arrangement of claim 11 , wherein calculating the electrical power loss in step c) is based at least on properties of the electric machine and a control strategy of the electric machine.

18. The electric drive arrangement of claim 11 , wherein the interval has a duration of at most 10 seconds.

19. The electric drive arrangement of claim 11 , wherein the interval has a duration of at least 0.5 seconds.

20. The electric drive arrangement of claim 11 , wherein the electric machine is a first drive unit of a motor vehicle; wherein the control unit is further programmed to, when a requested torque

Assignees

• Gkn Automotive Ltd

Inventors

• Gemassmer Tobias
• Cordero Enrique
• Sontheim Florian
• Fitz Rudolf

Classifications

• H02P23/14

  Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage · CPC title

• H02P29/68 Primary

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