Large transient detection for electric power generation

• US 20080157724A1
• Filed: 04/26/2007
• 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: Fattal, Souren G.
• Granted Patent: US 7,554,214 B2
• Time in Patent Office: Days
• US Class Current: 322/7
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: B60L 58/33 by cooling
• CPC Class Codes: H02P 2101/45 for motor vehicles, e.g. car alternators
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator
• CPC Class Codes: H02P 9/307 more than one voltage output
• CPC Class Codes: H02P 9/48 Arrangements for obtaining a constant output value at varying speed of the generator, e.g. on vehicle H02P9/04 - H02P9/46 take precedence
• 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
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

An electric power generation system is disclosed that provides an AC electric power output with the target waveform period. A sequence of values is established that each represent electric current of the output for a corresponding one of a number of sequential time segments. A processor executes operating logic to process the values for each respective one of the time segments that includes: determining a difference between a first one of the values and the second one of the values for the respective one of the time segments, selecting the second one of the values from the subset of values corresponding to a subset of the time segments, and performing a comparison of the difference to a threshold. Based on this comparison, a transient condition can be identified and/or control of the system can otherwise be facilitated.

Claims

1. A method, comprising:

operating an electric power generation system to provide an AC electric power output with a target waveform period;

establishing a sequence of values each representative of electric current of the output for a corresponding one of a number of sequential time segments, the time segments each being less than the target waveform period, for each of the time segments;

determining a difference between a first one of the values and a second one of the values, the first one of the values being more recent in the sequence of values than the second one of the values;

selecting the second one of the values from a subset of values corresponding to a subset of the time segments spanning more than the target waveform period;

performing a comparison of the difference to a threshold; and

controlling operation of the electric power generation system in accordance with the comparison.

2. The method of claim 1, which includes:

sampling the electric current of the output to provide a predefined number of current samples for each of the time segments; and

determining each of the values as a function of the predefined number of current samples for a different one of the time segments.

3. The method of claim 2, wherein the function corresponds to an average, and the threshold corresponds to a weighted current level.

4. The method of claim 1, wherein the second one of the values is the smallest of the subset.

5. The method of claim 1, which includes carrying the electric power generation system with a vehicle, the electric power generation system including a variable speed generator driven by an engine, a rectifier coupled the variable speed generator to a DC bus, an electrical energy storage device coupled to the DC bus, and an inverter coupled to the DC bus.

6. The method of claim 5, which includes:

providing the AC electric power output from the inverter at a target frequency corresponding to the target waveform period;

providing a first portion of the electric power the variable speed generator to the inverter through the rectifier and the DC bus; and

providing a second portion of the electric power form the variable speed generator to charge the electrical energy storage device through the rectifier and the DC bus;

7. The method of claim 6, which includes:

detecting start-up to two or more air conditioners powered from the inverter when the comparison exceeds the threshold;

responding to the start-up of the two or more air conditioners by discontinuing charging of the electrical energy storage device, providing DC power from the electrical energy storage device to the inverter through the DC bus, and increasing rotational speed of the variable speed generator to increase the electric power provided to the inverter through the rectified and the DC bus.

8. A method, comprising:

providing an electric power generation system to provide an AC electric power output at a target frequency;

for each waveform period of the output, performing a number of comparisons with values each representative of electric current of the AC electric power output for a different one of a number of time segments, the waveform period corresponding to the target frequency and the time segments each being less than the waveform period;

evaluating the comparisons to determine if a transient condition exists; and

adjusting operation of the system in response to the transient condition.

9. The method of claim 8, wherein the values each correspond to a function of a number of current samples taken over a corresponding one of the time segments.

10. The method of claim 8, wherein the performing of the comparisons includes determining a difference between two of the values for each of the time segments and comparing the difference to a threshold.

11. The method of claim 10, wherein a first one of the two of the values corresponds to a more recent one of the time segments than a second one of the two values, and the second one of the two values is a minimum of a subset of the values, the subset corresponding to a subset of the time segments spanning more than the waveform period.

12. The method of claim 8, which includes providing the electric power generation system with a vehicle, the vehicle including several air conditioners, the electric power generation system including a variable speed generator driven by an engine.

13. The method of claim 12, wherein the adjusting of the operation of the system includes increasing rotational speed of the generator in response to the transient condition.

14. The method of claim 13, which includes causing the transient condition by starting two or more of the air conditioners.

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 frequency AC power;

power circuitry electrically coupled to the generator to rectify the variable frequency AC power to provide DC power on a DC bus and an inverter to provide a regulated AC electric power output with a target waveform period from the DC bus;

a current sensor to detect electric current of the regulated AC electric power output;

a processor operatively coupled to the current sensor and the power circuitry, the processor executing operating logic to;

establish a sequence of values each representative of electric current of the output for a corresponding one of a number of sequential time segments, the time segments each being less than the target waveform period, determine a difference between a first one of the values and a second one of the values and compare the difference to a threshold for each of the time segments, determine a transient condition exists if the difference reaches the threshold for any of the time segments, and generate an output signal in response to the transient condition; and

wherein the engine is responsive to the output signal to increase rotational speed of the generator.

16. The system of claim 15, further comprising an electrical energy storage device coupled to the DC bus, the power circuitry including means for charging the electrical energy storage device.

17. The system of claim 16, further comprising means for providing power to the DC bus from the electrical energy storage device in response to the transient condition and means for disabling the charging means in response to the transient condition.

18. The system of claim 15, further comprising a vehicle carrying the engine, the variable speed generator, the power circuitry, a current sensing arrangement and the processor, and multiple air conditioners, the transient condition corresponding to start-up of two or more of the air conditioners.

19. The system of claim 15, wherein the operating logic includes means for selecting the second one of the values from a subset of the values, the second one of the values being the minimum of the subset, and the subset corresponding to a sequence of the time segments spanning more than the waveform period.

20. An apparatus, comprising:

an electric power generation system to provide an AC electric power output with a target waveform period;

means for establishing a sequence of values each representative of electric current of the output for a corresponding one of a number of sequential time segments, the time segments each being less than the target waveform period;

means for processing the values for each respective one of the time segments, the processing means including;

means for determining a difference between a first one of the values and a second one of the values for the respective one of the time segments, the first one of the values being more recent in the sequence of values than the second one of the values;

means for

selecting the second one of the values from a subset of values corresponding to a subset of the time segments spanning more than the target waveform period for the respective one of the time segments;

means for performing a comparison of the difference to a threshold; and

means for controlling operation of the electric power generation system in accordance with the comparison.