Method and system for controlling a power inverter in electric drives of vehicles with two-mode transmissions

• US 8,165,737 B2
• Filed: 10/24/2007
• Issued: 04/24/2012
• Est. Priority Date: 10/24/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Schulz, Steven E., West, Stephen T., Welchko, Brian A., Hiti, Silva
• Primary Examiner(s): Algahaim, Helal A
• Application Number:
  US11/923,287
• Publication Number:
  US 20090107742A1
• Time in Patent Office: 1,644 Days
• Field of Search: 701/22, 701/51, 318/342, 318/434, 180/65.7, 180/65.28, 180/65.51
• US Class Current: 701/22
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/52 Driving a plurality of drive axles, e.g. four-wheel drive
• CPC Class Codes: B60K 6/547 the transmission being a stepped gearing
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/15 Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: B60W 2710/083 Torque
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

Methods and systems for controlling a power inverter in automobiles utilizing two-mode transmissions are provided. The various embodiments control the power inverter by, responsive to a commanded torque of the electric motor being below a first torque level, controlling the power inverter to set a switching frequency of the power inverter at a first set frequency; and, responsive to the commanded torque of the electric motor being between the first torque level and a second torque level, controlling the power inverter to determine the switching frequency of the power inverter as a function of the commanded torque of the electric motor while maintaining the switching frequency above a dynamic frequency limit. The method reduces switching frequencies in the inverter at high commanded torques, while maintaining the switching frequencies above dynamic frequency limit that provides effective control over the motor.

Claims

1. A method for controlling a power inverter coupled to an electric motor in an electric drive system of an automobile, wherein the electric drive system includes a prime mover power source, a two-mode, compound-split, electro-mechanical transmission coupled to the prime mover power source, the electro-mechanical transmission comprising a first motor and a second motor, wherein the power inverter is coupled to the first and second motors, the method comprising:

responsive to a commanded torque of the first motor being below a first torque level, controlling, by a processor, the power inverter to set a switching frequency of the power inverter at a first set frequency; and

responsive to the commanded torque of the first motor being between the first torque level and a second torque level, controlling, by the processor, the power inverter to determine the switching frequency of the power inverter as a function of the commanded torque of the electric motor while maintaining the switching frequency above a dynamic frequency limit.

2. The method of claim 1, wherein the dynamic frequency limit is determined by:

responsive to the motor speed of the first motor being between a first speed level and a second speed level, determining the dynamic frequency limit as a function of the motor speed; and

responsive to the motor speed being below the first speed level, determining the dynamic frequency limit to set the dynamic frequency limit at a second set frequency.

3. The method of claim 2, wherein the dynamic frequency limit is further determined by, responsive to the motor speed being above second speed level, determining the dynamic frequency limit to set the dynamic frequency limit at the first set frequency.

4. The method of claim 2, wherein the step of determining the dynamic frequency limit as a function of the motor speed comprises determining the dynamic frequency limit to maintain a set pulse ratio of switching frequency to the motor speed.

5. The method of claim 1, wherein the step of controlling the power inverter to determine the switching frequency of the power inverter as a function of the commanded torque of the electric motor while maintaining the switching frequency above the dynamic frequency limit comprises decreasing the switching frequency as the commanded torque increases.

6. The method of claim 1, wherein the step of controlling the power inverter to determine the switching frequency of the power inverter as a function of the commanded torque of the electric motor while maintaining the switching frequency above the dynamic frequency limit comprises determining the switching frequency as:

7. The method of claim 1, wherein the electric drive system includes a second power inverter corresponding to the second motor, further comprising:

responsive to a second commanded torque of the second motor being below the first torque level, controlling the second power inverter to set a switching frequency of the second power inverter at a first set frequency; and

responsive to the commanded torque of the second motor being between the first torque level and a second torque level, controlling the second power inverter to determine the switching frequency of the second power inverter as the function of the commanded torque of the electric motor while maintaining the switching frequency above the dynamic frequency limit.

8. An automotive electric drive system comprising:

a prime mover power source;

a two-mode, compound-split, electro-mechanical transmission coupled to the prime mover power source, the electro-mechanical transmission comprising first and second motors;

a power inverter coupled to the first and second motors; and

a processor coupled to the first and second motors and the power inverter, the processor being configured to;

responsive to a commanded torque of the first motor being below a first torque level, provide a signal controlling the power inverter to set a switching frequency of the power inverter at a first set frequency;

responsive to the commanded torque of the first motor being between the first torque level and a second torque level, provide a signal controlling the power inverter to determine the switching frequency of the power inverter as a function of the commanded torque of the electric motor while maintaining the switching frequency above a dynamic frequency limit.

9. The automotive drive system of claim 8, wherein the electro-mechanical transmission further comprises:

an input member to receive power from the prime mover;

an output member to deliver power from the electro-mechanical transmission;

first, second, and third coaxially-aligned planetary gear arrangements, each planetary gear arrangement utilizing first, second and third gear members, the first and second motors being coaxially aligned with each other and with the three planetary gear arrangements, at least one of the first, second, and third gear members in the first or second planetary gear arrangement being connected to the first motor, and another one of the first, second, and third gear members in the second and third planetary gear arrangements being connected to the second motor, one of the gear members of the first planetary gear arrangement being continuously connected to the input member;

a first torque-transmitting mechanism to selectively connect one of the gear members associated with each of the planetary gear arrangements to each other and to the output member;

a second torque-transmitting mechanism to selectively connect one of the gear members of the third planetary gear set with ground;

a third torque-transmitting mechanism to selectively connect one of the gear members of the second planetary gear set with another of the gear members of the second planetary gear set;

a first interconnecting member continuously connecting one of the members of the first planetary gear set with one of the members of the second planetary gear set; and

a second interconnecting member continuously connecting one of the members of the second planetary gear set with one of the members of the third planetary gear set.

10. The automotive electric drive system of claim 9, wherein the processor is further configured to:

responsive to the motor speed of the first motor being between a first speed level and a second speed level, determine the dynamic frequency limit as a function of the motor speed; and

responsive to the motor speed being below the first speed level, determine the dynamic frequency limit to set the dynamic frequency limit at a second set frequency.

11. The automotive electric drive system of claim 10, wherein the processor is further configured to, responsive to the motor speed being above second speed level, determine the dynamic frequency limit to set the dynamic frequency limit at the first set frequency.

12. The automotive electric drive system of claim 11, wherein the processor is configured to determine the dynamic frequency limit as a function of the motor speed to maintain a set pulse ratio of switching frequency to the motor speed.

13. The automotive electric drive system of claim 8, wherein the function of the commanded torque decreases the switching frequency as the commanded torque increases.

14. The automotive electric drive system of claim 8, wherein the function of the commanded torque comprises:

15. The automotive electric drive system of claim 8, wherein the electric drive system includes a second power inverter corresponding to the second motor, and wherein the processor is further configured to:

responsive to a second commanded torque of the second motor being below the first torque level, controlling the second power inverter to set a switching frequency of the second power inverter at a first set frequency; and

responsive to the commanded torque of the second motor being between the first torque level and a second torque level, controlling the second power inverter to determine the switching frequency of the second power inverter as the function of the commanded torque of the electric motor while maintaining the switching frequency above the dynamic frequency limit.

16. An automotive drive system comprising:

a prime mover power source;

a two-mode, compound-split, electro-mechanical transmission coupled to the prime mover power source, the electro-mechanical transmission comprising;

an input member to receive power from the prime mover;

an output member to deliver power from the electro-mechanical transmission;

first and second motors being coaxially aligned;

first, second, and third coaxially aligned planetary gear arrangements, each planetary gear arrangement utilizing first, second and third gear members, the first and second motors being coaxially aligned with the three planetary gear arrangements, at least one of the first, second, and third gear members in the first or second planetary gear arrangement being connected to the first motor, and another one of the first, second, and third gear members in the second and third planetary gear arrangements being connected to the second motor, one of the gear members of the first planetary gear arrangement being continuously connected to the input member;

a first torque-transmitting mechanism to selectively connect one of the gear members associated with each of the planetary gear arrangements to each other and to the output member;

a second torque-transmitting mechanism to selectively connect one of the gear members of the third planetary gear set with ground;

a third torque-transmitting mechanism to selectively connect one of the gear members of the second planetary gear set with another of the gear members of the second planetary gear set;

a first interconnecting member continuously connecting one of the members of the first planetary gear set with one of the members of the second planetary gear set; and

a second interconnecting member continuously connecting one of the members of the second planetary gear set with one of the members of the third planetary gear set;

a power inverter coupled to the first and second motors;

an energy storage device coupled to the power inverter; and

a processor coupled to the first and second motors and the power inverter, the processor being configured to;

responsive to a commanded torque of the first motor being below a first torque level, provide a signal controlling the power inverter to set a switching frequency of the power inverter at a first set frequency;

responsive to the commanded torque of the first motor being between the first torque level and a second torque level, provide a signal controlling the power inverter to determine the switching frequency of the power inverter as a function of the commanded torque of the electric motor while maintaining the switching frequency above a dynamic frequency limit;

wherein the function of the commanded torque is selected to decrease switching frequency as the commanded torque increases, and wherein the dynamic frequency limit determined by;

responsive to the motor speed of the first motor being between a first speed level and a second speed level, determining the dynamic frequency limit as a function of the motor speed to maintain set pulse ratio of motor switching frequency to motor speed;

responsive to the motor speed being below the first speed level, determining the dynamic frequency limit to set the dynamic frequency limit at a second set frequency; and

responsive to the motor speed being above second speed level, determining the dynamic frequency limit to set the dynamic frequency limit at the first set frequency.

17. The automotive electric drive system of claim 16, wherein the function of the commanded torque comprises: