Electric power generation system with current-controlled power boost

• US 20080157592A1
• Filed: 06/01/2007
• Published: 07/03/2008
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: Cummins Power Generation IP, Inc.
• Original Assignee: Cummins Power Generation IP, Inc.
• Inventors: Bax, Randall L., Peterson, Mitchell E., Naden, Mark
• Granted Patent: US 7,855,466 B2
• Time in Patent Office: Days
• US Class Current: 307/10.1
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02P 2201/09 Boost converter, i.e. DC-DC step up converter increasing the voltage between the supply and the inverter driving the motor general aspects of plural converters in cascade H02M
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• 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
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

An electric power system includes a variable speed generator driven by an engine and an electrical energy storage device. The generator and the storage device are coupled to a variable voltage DC bus. An inverter converts DC electricity from the DC bus to AC electricity for one or more electrical loads. A detector is included to monitor electric current provided to the DC bus by the storage device and provide a corresponding signal. Control circuitry is responsive to this signal to regulate power output from the storage device to the DC bus.

Claims

1. A method, comprising:

driving a variable speed electric power generator with an engine to provide a first portion of electric power to one or more electrical loads;

from an electrical energy storage device, providing a second portion of the electric power to the one or more electrical loads;

monitoring electric current through the electrical energy storage device; and

while providing the second portion of the electric power, controlling electric power output from the electrical energy storage device in accordance with the electric current.

2. The method of claim 1, which includes:

measuring the electric power provided to the one or more electric loads;

determining a current control reference as a function of the electric power and capacity of the generator; and

performing the controlling of the electric power output based on a difference between the electric current and the current control reference.

3. The method of claim 1, which includes:

providing the first portion of the electric power to a DC bus from the generator through a rectifier;

providing the second portion of the electric power to the DC bus from the electrical energy storage device through a DC-to-DC converter; and

inverting DC power from the DC bus to provide AC power to the one or more electrical loads.

4. The method of claim 3, which includes varying a voltage on the DC bus over a range that extends from a nonzero minimum to a nonzero maximum with the nonzero minimum being 75% or less of the nonzero maximum while providing the AC power to the one or more electrical loads.

5. The method of claim 1, which includes:

detecting a transient power condition; and

adjusting the electric power output from the electrical energy storage device in response to the transient power condition.

6. The method of claim 5, which includes:

installing the generator, the engine, and the storage device in a vehicle;

carrying the one or more electrical loads with the vehicle; and

electrically coupling the one or more electrical loads to an inverter, the inverter being coupled to a DC bus, the DC bus being coupled to the generator and the storage device installed in the vehicle.

7. The method of claim 1, wherein the storage device includes one or more electrochemical batteries, and which includes:

determining an amount of the electric power provided to the one or more loads; and

providing a current-controlled adjustment to the one or more batteries in response to the amount of the electric power;

disabling the electric power output from the one or more batteries; and

charging the one or more batteries with electricity from the generator after the disabling of the electric power output.

10. The method of claim 3, which includes varying a voltage on the DC bus over a range that extends from a nonzero minimum to a nonzero maximum with the nonzero minimum being 75% or less of the nonzero maximum while regulating the electric power.

8. A method, comprising:

operating a variable speed electric power generator and an electrical energy storage device coupled to a variable voltage DC bus;

providing electric power to one or more electric loads from the DC bus;

determining electric current flow between the electrical energy storage device and the DC bus; and

regulating electric power provided from the electrical energy storage device to the DC bus as a function of the electric current flow.

9. The method of claim 8, which includes:

measuring the electric power provided to the one or more electric loads;

determining a current control reference as a function of the electric power and capacity of the generator; and

performing the regulating of the electric power as a function to the electric current flow and the current control reference.

11. The method of claim 8, which includes:

detecting a transient power condition; and

adjusting the electric power from the storage device in response to the transient power condition.

12. The method of claim 8, which includes driving the generator with a variable speed engine.

13. The method of claim 12, which includes:

installing the generator, the engine, and the storage device in a motor coach;

carrying the one or more electric loads with the motor coach; and

electrically coupling the one or more electric loads to an inverter, the inverter being coupled to the DC bus.

14. The method of claim 8, wherein the storage device includes one or more electrochemical batteries, and which includes:

disabling the electric power output from the one or more batteries; and

charging the one or more batteries from the DC bus with electric power output by the generator after the disabling of the electric power output.

15. A system, comprising:

an engine;

a variable speed generator mechanically coupled to the engine, the engine being structured to drive the generator to provide variable AC power;

an electrical energy storage device to selectively supply variable DC power;

a variable voltage DC bus coupled to the generator and the electrical energy storage device;

an inverter coupled to the DC bus to provide an AC power output;

a detector to monitor electric current through the electrical energy storage device to provide a corresponding detector signal; and

control circuitry coupled to the DC bus to regulate power output from the electrical energy storage device as a function of the detector signal and a current control reference.

16. The system of claim 15, wherein the control circuitry defines a proportional-integral regulator.

17. The system of claim 15, wherein the control circuitry includes means for comparing the electric current and the current reference.

18. The system of claim 17, wherein the circuitry includes a processor programmed to provide the comparing means and means for determining the current control reference based on power demand for the AC power output and power capacity of the generator.

19. The system of claim 15, further comprising a bidirectional DC-to-DC converter coupled between the DC bus and the storage device.

20. The system of claim 19, wherein the detector includes a current transformer positioned along an electrically conductive pathway between the storage device and the bidirectional DC-to-DC converter.