Method and apparatus for preventing excessive reaction to a load disturbance by a generator set

• US 6,555,929 B1
• Filed: 10/24/2000
• Issued: 04/29/2003
• Est. Priority Date: 10/24/2000
• Status: Active Grant

• Current Assignee: Kohler Company
• Original Assignee: Kohler Company
• Inventors: Albsmeier, Eric, Lindgren, Michael S., Eaton, Zane C.
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): GONZALEZ, JULIO CESAR
• Application Number:
  US09/695,168
• Time in Patent Office: 917 Days
• Field of Search: 322/28, 322/17, 322/90, 322/44, 322/89, 322/29, 318/139, 606/68, 180/65.4
• US Class Current: 290/40.00B
• CPC Class Codes: F02D 11/105 characterised by the function converting demand to actuation, e.g. a map indicating relations between an accelerator pedal position and throttle valve opening or target engine torque
• CPC Class Codes: F02D 2041/141 using a feed-forward control element
• CPC Class Codes: F02D 31/002 controlling air supply
• CPC Class Codes: F02D 41/083 taking into account engine load variation, e.g. air-conditionning
• CPC Class Codes: H02P 9/102 for limiting effects of transients

Abstract

A method and apparatus are disclosed for controlling a genset having an engine and an alternator in order to prevent an excessive change in a speed of the engine because of a sudden change in a load on the alternator. The method includes obtaining a first measured value of an actual AC output power of the alternator at a genset controller during a first time period, and obtaining a second measured value of the actual AC output power of the alternator at the genset controller during a second time period. The method further includes determining at the genset controller a first output power based upon at least the first measured value, and a second output power based upon at least the second measured value. The method additionally includes determining at the genset controller, based upon the first output power and the second output power, whether the actual AC output power has changed in an amount greater than a first threshold, and providing a first control signal from the genset controller to the genset causing a position of a throttle to be modified when it is determined that the actual AC output power has changed in an amount greater than the first threshold.

Claims

1. A method of controlling a genset having an engine and an alternator in order to prevent an excessive change in a speed of the engine because of a sudden change in a load on the alternator, the method comprising:

obtaining a first measured value of an actual AC output power of the alternator at a genset controller during a first time period;

obtaining a second measured value of the actual AC output power of the alternator at the genset controller during a second time period;

determining at the genset controller a first output power based upon at least the first measured value, and a second output power based upon at least the second measured value;

determining at the genset controller, based upon the first output power and the second output power, whether the actual AC output power has changed in an amount greater than a first threshold; and

providing a first control signal from the genset controller to the genset causing a position of a throttle to be modified when it is determined that the actual AC output power has changed in an amount greater than the first threshold.

2. The method of claim 1, wherein it is determined whether the actual AC output power has increased in an amount greater than the first threshold by comparing a ratio of the second output power to the first output power with a first threshold value, and the first control signal causes the throttle to be opened in response to the determination that the actual AC output power has increased in an amount greater than the first threshold.

3. The method of claim 2, further comprising:

obtaining a measurement of the speed of the engine;

determining whether a difference between the measurement and a nominal speed is less than a second threshold; and

providing a second control signal from the genset controller to the genset causing control of the throttle to be released to an engine governor of the genset when it is determined that the difference is less than the second threshold.

4. The method of claim 3, wherein the second control signal causes the throttle to close.

5. The method of claim 3, wherein the second threshold is at least one of 25 RPM and a predefined value.

6. The method of claim 2, further comprising:

obtaining a first plurality of additional values of the actual AC output power of the alternator at the genset controller during the first time period; and

obtaining a second plurality of additional values of the actual AC output power of the alternator at the genset controller during the second time period,

wherein the genset controller determines the first output power based upon the first measured value and the first plurality of additional values, and determines the second output power based upon the second measured value and the second plurality of additional values.

7. The method of claim 6, wherein the genset controller determines the first output power as the average of the first measured value and each of the first plurality of additional values, and determines the second output power as the average of the second measured value and each of the second plurality of additional values.

8. The method of claim 6, wherein the alternator is configured to operate at a frequency of 50 Hertz, and each of the first and second pluralities of additional values includes 18 additional values.

9. The method of claim 6, wherein the alternator is configured to operate at a frequency of 60 Hertz, and each of the first and second pluralities of additional values includes 15 additional values.

10. The method of claim 6, wherein the genset controller determines whether the actual AC output power has increased in an amount greater than the first threshold by calculating the ratio of the second output power to the first output power.

11. The method of claim 10, wherein the genset controller determines that the actual AC output power has increased in amount greater than the first threshold when the genset controller calculates that the ratio of the second output power to the first output power is greater than 1.3.

12. The method of claim 2, wherein the magnitude of the first control signal, and consequently the degree to which the throttle is caused to open, varies in dependence upon the degree to which the actual AC output power has increased.

13. The method of claim 2, further comprising:

obtaining at least two measurements of the speed of the engine;

calculating a slope of the speed of the engine;

determining whether the slope exceeds a second threshold; and

providing a second control signal from the genset controller to the genset causing the throttle to close when it is determined that the slope exceeds the second threshold.

14. The method of claim 3,

wherein the providing of the first control signal continues after it is determined that the actual AC output power has increased in the amount greater than the first threshold, and

wherein the magnitude of the first control signal that is provided varies in dependence upon the difference between the speed of the engine and the nominal speed until it is determined that the difference between the measurement and the nominal speed is less than the second threshold.

15. An apparatus for controlling a genset having an engine and an alternator in order to prevent an excessive change in a speed of the engine because of a sudden change in a load on the alternator, the apparatus comprising:

a first input terminal configured to receive at least a first measured value and a second measured value of an actual AC output power of an alternator of the genset;

a processor coupled to the first input terminal, wherein the processor is configured to determine a first output power and a second output power based upon at least the first measured value and at least the second measured value, respectively, and to determine, based upon the first output power and the second output power, whether the actual AC output power has changed in an amount greater than a first threshold; and

a first output terminal coupled to the processor and configured to provide a first output signal to the genset causing a position of a throttle on the genset to be modified when the processor determines that the actual AC output power of the alternator has changed in an amount greater than the first threshold.

16. The apparatus of claim 15, further comprising:

a second input terminal coupled to the processor, the terminal being configured to receive a measurement of the speed of the engine,

wherein the processor is configured to determine whether a difference between the measurement and a nominal speed is less than a second threshold, and

wherein the first output terminal is configured to provide a second control signal from the genset controller to the genset causing control of the throttle to be released to an engine governor of the genset when it is determined that the difference is less than the second threshold.

17. The apparatus of claim 16, wherein the processor includes a microprocessor, wherein it is determined whether the actual AC output power has increased in an amount greater than the first threshold and, if the actual AC output power has been determined to have increased in an amount greater than the first threshold, the throttle is opened.

18. The apparatus of claim 16, wherein the first input terminal is a three-phase input interface, and the second input interface and the first output terminal are a CAN interface.

19. An apparatus for converting mechanical energy into electrical energy comprising:

a genset including an engine coupled to an alternator;

an engine control module coupled to the genset;

a means for monitoring an actual AC output power of the alternator, for determining whether the actual AC output power has increased in an amount greater than a first threshold, and for providing a first signal to the engine control module in order to cause an opening of a throttle of the engine when it is determined that the actual AC output power has increased in an amount greater than the first threshold; and

a means for monitoring the speed of the engine, for determining whether a difference between the speed and a nominal speed is less than a second threshold, and for providing a second signal to the engine control module causing control of the throttle to be released to at least one of the engine control module and the engine when it is determined that the difference is less than the second threshold.

20. The apparatus of claim 19, wherein the means for determining whether the actual AC output power has increased in an amount greater than a first threshold determines an increase in the actual AC output power by comparing a first average of a first plurality of power measurements with a second average of a second plurality of power measurements.