Electric drive system having DC bus voltage control

• US 20050263331A1
• Filed: 10/29/2004
• Published: 12/01/2005
• Est. Priority Date: 05/25/2004
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Guven, Mustafa, Sopko, Tom, Kuras, Brian
• Granted Patent: US 7,298,102 B2
• Time in Patent Office: Days
• US Class Current: 180/65.100
• CPC Class Codes: B60K 6/46 Series type
• CPC Class Codes: B60L 2200/40 Working vehicles
• CPC Class Codes: B60L 2220/18 Reluctance machines
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• 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 20/10 Controlling the power contribution of each of the prime movers to meet required power demand
• CPC Class Codes: B60W 2300/17 Construction vehicles, e.g. graders, excavators
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/16 Information or communication technologies improving the operation of electric vehicles

Abstract

An electric drive system has a power source and a generator operatively connected to the power source. The electric drive system also has at least one energy storage device such as a capacitor configured to store a supply of power. The electric drive system further has a common bus configured to direct the power output to the capacitor. The electric drive system also has at least one motor configured to receive power from the common bus. A controller for the electric drive system is provided, having an article therewith having a computer readable medium with a control algorithm recorded thereon. The control algorithm includes means for compensating for a change in power demand on a DC bus of the electric drive system

Claims

1. An article comprising:

a computer readable medium having a control algorithm recorded thereon;

said algorithm including means for compensating for a change in power demand on a DC bus having an electric motor and a generator connected therewith;

said means for compensating including means for commanding a current change at a DC to DC converter coupling an energy storage device with said DC bus such that the change in power demand is primarily compensated for by the energy storage device rather than the generator, if a stored energy of said energy storage device is within a predetermined middle range.

2. The article of claim 1 wherein said means for compensating includes means for commanding a current change at said DC to DC converter such that the change in power demand is compensated for solely by said energy storage device, if the stored energy of said energy storage device is within said predetermined middle range.

3. The article of claim 2 wherein said means for compensating includes means for adjusting a power output of said generator to said DC bus such that the change in power demand is compensated for at least partially by said generator, if the stored energy of said energy storage device is outside of said predetermined middle range.

4. The article of claim 3 wherein said means for compensating includes means for adjusting a power output of said generator to said DC bus such that the change in power demand is compensated for in part by said generator and in part by said energy storage device, if the stored energy of said energy storage device is outside of said predetermined middle range but within predetermined upper or lower ranges.

5. The article of claim 4 wherein said means for compensating includes means for adjusting a power output of said generator to said DC bus such that the change in power demand is compensated for primarily by said generator, if the stored energy of said energy storage device is outside of said predetermined upper, lower and middle ranges.

6. The article of claim 5 wherein said means for compensating includes means for increasing a power output of said generator to said DC bus, if the stored energy of said energy storage device is within or below said predetermined lower range.

7. The article of claim 6 wherein said means for compensating includes means for decreasing a power output of said generator to said DC bus, if the stored energy of said energy storage device is within or above said predetermined upper range.

8. The article of claim 7 wherein said control algorithm includes means for returning the stored energy of said energy storage device toward a target quantity of stored energy, if the stored energy of said energy storage device is outside the predetermined middle range.

9. The article of claim 8 wherein said means for returning includes means for commanding a generator output change and a current change at said DC to DC converter to drive the stored energy of the energy storage device toward said predetermined middle range.

10. The article of claim 9 wherein said means for returning includes means for commanding a current change at said DC to DC converter to lower a quantity of stored energy of said energy storage device, if the stored energy of said energy storage device is above said predetermined middle range.

11. The article of claim 9 wherein said means for returning includes means for selectively commanding a decrease in power output of said generator to offset in said DC bus at least a portion of stored energy discharged to said DC bus by said energy storage device.

12. An electric drive system for a work machine comprising:

an electronic control module with the article of claim 1, said electronic control module being operable to control a voltage of said DC bus;

said electronic control module being in control communication with said generator, said motor and said DC to DC converter and being operable to command a torque of said generator and said motor, and to command a current at said DC to DC converter;

said electronic control module further being operable to partition a power flow among said generator, said motor and said DC to DC converter based at least in part on the quantity of stored energy of said energy storage device, wherein said energy storage device comprises a supercapacitor.

13. A method of controlling a power supply to a DC bus in an electric drive system having a generator and a motor coupled with the DC bus, said method comprising the step of:

compensating for a change in power demand on the DC bus at least in part with an energy storage device by commanding a current change at a DC to DC converter coupling the energy storage device with the DC bus, if a stored energy of the energy storage device is within a predetermined middle range.

14. The method of claim 13 wherein the step of compensating for the change in power demand on the DC bus with the energy storage device comprises:

compensating for the change in power demand solely with the energy storage device, if the stored energy thereof is within the predetermined middle range.

15. The method of claim 13 comprising the step of:

compensating for the change in power demand on the DC bus at least in part with the generator by commanding an increase or a decrease in the power output of the generator, if the stored energy of the energy storage device is outside of the predetermined middle range.

16. The method of claim 13 comprising the step of:

compensating for the change in power demand on the DC bus in part with the generator and in part with the energy storage device, if the stored energy of the energy storage device is outside of the predetermined middle range but within one of a predetermined upper or lower range.

17. The method of claim 16 wherein the step of compensating for the change in power demand on the DC bus comprises:

compensating for the change in power demand solely with the generator, if the stored energy of the energy storage device is outside of the predetermined middle, upper and lower ranges.

18. The method of claim 17 comprising the step of:

returning the stored energy of the energy storage device toward a target quantity of stored energy at least in part by commanding a current flow at the DC to DC converter, if the stored energy of the energy storage device is outside the predetermined middle range.

19. The method of claim 18 wherein the step of returning the stored energy of the energy storage device toward a target quantity comprises adjusting the power output or rate of change in the power output of the generator, if the stored energy of the energy storage device is outside the predetermined middle range.

20. A work machine comprising:

an electric drive system with a power supply to a DC bus controlled according to the method of claim 13;

and

wherein said energy storage device includes a capacitor.