Over-voltage and under-voltage management for electric drive system

• US 7,795,825 B2
• Filed: 09/15/2008
• Issued: 09/14/2010
• Est. Priority Date: 09/15/2008
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Williams, Joshua
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US12/210,881
• Publication Number:
  US 20100066288A1
• Time in Patent Office: 729 Days
• Field of Search: 318/143, 318/146, 318/156, 318/362, 318/376, 318/455, 318/430, 318/453, 361/31, 361/33, 180/65.1, 180/54.1
• US Class Current: 318/156
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: H02P 29/032 Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A method of voltage supply management for an electric drive system includes receiving a voltage signal (1002) indicative of a voltage in a supply link, and one or more condition signals that are indicative of an operating condition of the electric drive system. A difference between a desired voltage value (1008), which is calculated based on the voltage signal (1002) and the one or more condition signals, and the voltage signal (1002) yields a voltage error signal (1014). The voltage error signal (1014) is evaluated to indicate an over-voltage condition or an under-voltage condition. Power is dissipated from the supply link when an over-voltage condition is present and a torque command limit with respect to the one or more electric drive motors (210) is imposed when an under-voltage condition is present.

Claims

1. A method of voltage supply management for an electric drive system, the electric drive system including a fuel-driven engine having an output for driving an electrical power generator, the electrical power generator providing power to one or more electric drive motors via a supply link, the method comprising:

receiving a voltage signal indicative of a voltage in the supply link;

receiving one or more condition signals indicative of an operating condition of the electric drive system;

calculating a desired voltage value based on the voltage signal and the one or more condition signals;

differencing the desired voltage value and the voltage signal to yield a voltage error signal indicating an extent to which the voltage signal diverges from the desired voltage value; and

determining whether the voltage error signal is indicative of an over-voltage condition or of an under-voltage condition and dissipating power from the supply link if the voltage error signal is indicative of the over-voltage condition, and imposing a torque command limit with respect to the one or more electric drive motors if the voltage error signal is indicative of the under-voltage condition.

2. The method according to claim 1, wherein the one or more condition signals indicative of the operating condition of the electric drive system include at least one of an operator input, a machine speed, an electric drive motor speed, an engine speed, an engine load, an excitation current provided to the electrical power generator, an excitation voltage provided to the electrical power generator, and an activation state of a retard system associated with a machine.

3. The method according to claim 1, wherein calculating the desired voltage value based on the voltage signal and the one or more condition signals employs a look-up function to identify the desired voltage value.

4. The method according to claim 3, wherein the look-up function includes a multidimensional data array linking candidate desired voltage values with multiple machine operating conditions.

5. The method according to claim 3, wherein the look-up function includes a model-based algorithm for yielding the desired voltage value.

6. The method according to claim 1, further including limiting the desired voltage value to be greater than a lower voltage limit.

7. The method according to claim 1, further including limiting the desired voltage value to be less than an upper voltage limit.

8. The method according to claim 1, wherein the electric drive system includes a resistive grid switchably connected across the supply link, and wherein the step of dissipating power from the supply link includes connecting the resistive grid across the supply link.

9. A computer-readable medium having thereon computer-executable instructions for performing voltage supply management for an electric drive system, the electric drive system including a fuel-driven engine having an output for driving an electrical power generator, the electrical power generator providing power to one or more electric drive motors via a supply link, the computer-executable instructions comprising:

instructions for receiving a voltage signal indicative of a voltage in the supply link;

instructions for receiving one or more condition signals indicative of an operating condition of the electric drive system;

instructions for calculating a desired voltage value based on the voltage signal and the one or more condition signals;

instructions for differencing the desired voltage value and the voltage signal to yield a voltage error signal indicating an extent to which the voltage signal diverges from the desired voltage value; and

instructions for determining whether the voltage error signal is indicative of an over-voltage condition or of an under-voltage condition and dissipating power from the supply link if the voltage error signal is indicative of the over-voltage condition, and imposing a torque command limit with respect to the one or more electric drive motors if the voltage error signal is indicative of the under-voltage condition.

10. The computer-readable medium according to claim 9, wherein the one or more condition signals indicative of the operating condition of the electric drive system include at least one of an operator input, a machine speed, an electric drive motor speed, an engine speed, an engine load, an excitation current provided to the electrical power generator, an excitation voltage provided to the electrical power generator, and an activation state of a retard system associated with a machine.

11. The computer-readable medium according to claim 9, wherein the instructions for calculating the desired voltage value based on the voltage signal and the one or more condition signals include instructions for utilizing a look-up function to identify the desired voltage value.

12. The computer-readable medium according to claim 11, wherein the look-up function includes a multidimensional data array linking candidate desired voltage values with multiple machine operating conditions.

13. The computer-readable medium according to claim 11, wherein the look-up function includes a model-based algorithm for yielding the desired voltage value.

14. The computer-readable medium according to claim 9, further including instructions for limiting the desired voltage value to be greater than a lower voltage limit.

15. The computer-readable medium according to claim 9, further including instructions for limiting the desired voltage value to be less than an upper voltage limit.

16. The computer-readable medium according to claim 9, wherein the electric drive system includes a resistive grid switchably connected across the supply link, and wherein dissipating power from the supply link includes connecting the resistive grid across the supply link.

17. A controller for controlling an electric drive system and for executing voltage supply management for the electric drive system, the electric drive system including a fuel-driven engine having an output for driving an electrical power generator, the electrical power generator providing power to one or more electric drive motors via a supply link, the controller comprising:

an input for receiving a voltage signal indicative of a voltage in the supply link;

an input for receiving one or more condition signals indicative of an operating condition of the electric drive system; and

a processor for conforming the voltage in the supply link to a desired voltage value associated with the voltage signal and the one or more condition signals by dissipating power from the supply link if the desired voltage value is less than the voltage signal, and imposing a torque command limit with respect to the one or more electric drive motors if the desired voltage value is greater than the voltage signal.

18. The controller according to claim 17, wherein the processor is programmed to limit the desired voltage value to be greater than a lower voltage limit.

19. The controller according to claim 17, wherein the processor is programmed to limit the desired voltage value to be less than an upper voltage limit.

20. The controller according to claim 17, wherein the electric drive system includes a resistive grid switchably connected across the supply link, and wherein the processor is adapted to dissipate power from the supply link by selectively connecting the resistive grid across the supply link.