Transformerless, load adaptive speed controller

• US 20050140142A1
• Filed: 02/25/2005
• Published: 06/30/2005
• Est. Priority Date: 10/22/2002
• Status: Active Grant

• Current Assignee: The Switch Controls and Converters, Inc.
• Original Assignee: Youtility Incorporated
• Inventors: Hohm, Daniel P., Wen, Jian, Welches, Richard Shaun
• Granted Patent: US 6,969,922 B2
• Time in Patent Office: Days
• US Class Current: 290/41
• CPC Class Codes: H02J 3/00125 Transmission line or load transient problems, e.g. overvoltage, resonance or self-excitation of inductive loads H02J3/01 takes precedence
• CPC Class Codes: H02J 3/01 Arrangements for reducing harmonics or ripples
• CPC Class Codes: H02J 3/1864 wherein the stepless control of reactive power is obtained by at least one reactive element connected in series with a semiconductor switch
• CPC Class Codes: H02J 3/30 using dynamo-electric machines coupled to flywheels
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H02P 2101/45 for motor vehicles, e.g. car alternators
• 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: Y02E 40/40 Arrangements for reducing harmonics
• CPC Class Codes: Y02E 60/16 Mechanical energy storage, e.g. flywheels or pressurised fluids

Abstract

The invention in one embodiment is an improved variable speed engine/generator set with an integrated power conditioning system and control method including load shedding to generate high quality AC power with improved fuel efficiency and reduced emissions. The variable speed generator control scheme allows for load adaptive speed control of engine and generator field. The transformerless power inverter topology and control method provides the necessary output frequency, voltage and/or current waveform regulation, harmonic distortion rejection, and provides for single phase, or unbalanced loading.

Claims

1. A method for producing quality AC output power to a load, comprising:

measuring a set of properties of an actual load output;

measuring a speed of a variable speed energy generating device;

calculating a speed command signal using said speed and said properties;

converting said speed command signal into a throttle adjustment signal; and

adjusting said speed of said variable speed energy generating device using said throttle adjustment signal, thereby adjusting said AC output power to said load.

2. The method according to claim 1, further comprising responding to an increased load by calculating a load shed term and reducing a portion of said load based on said load shed term.

3. The method according to claim 2, wherein said portion is a percentage of a power margin of said variable speed energy generating device.

4. The method according to claim 1, further comprising responding to an increased load by setting said speed command at about a maximum.

5. The method according to claim 1, further comprising responding to an increased load by calculating a load shed term, reducing a portion of said load based on said load shed term, and setting said speed command at about a maximum.

6. The method according to claim 1, further comprising measuring a throttle position and calculating said speed command signal using said speed, said properties, and said throttle position.

7. The method according to claim 1, wherein said set of properties is selected from the group consisting of:

voltages of each phase, currents of each phase, and phase angles of each phase.

8. The method according to claim 1, further comprising regulating a generator of said variable speed energy generating device by adjusting a field voltage.

9. The method according to claim 1, further comprising applying an adaptive speed loop gain algorithm.

10. The method according to claim 1, further comprising responding to an increased load by decreasing an inverter output AC voltage.

11. A method for regulating a variable speed generator, comprising:

measuring an actual load output;

measuring a speed of said variable speed generator;

deriving a speed command signal from said measuring;

converting said speed command signal into a throttle adjustment signal;

adjusting said speed of said variable speed generator using said throttle adjustment signal;

inverting an output of said variable speed generator thereby producing an AC power generation.

12. The method according to claim 11, further comprising deriving a second speed command and calculating a load shed term.

13. The method according to claim 11, further comprising shedding a portion of said load and increasing said speed command as a fast response to an increase in said load

14. The method according to claim 11, further comprising responding to an increased load by boosting said variable speed generator.

15. The method according to claim 11, wherein said speed command is derived using at least one look-up table.

16. The method according to claim 11, further comprising applying an offset speed command.

17. The method according to claim 11, further comprising measuring a throttle position of said variable speed generator.

18. The method according to claim 11, further comprising applying an external overload warning signal prior to an overload.

19. A system for regulating a variable speed generator and preventing stalling, comprising:

measuring a set of properties of an actual load output;

measuring a speed of a variable speed energy generating device;

calculating a speed command signal using apriori information about said variable speed generator;

deriving a load shed term;

converting said speed command signal into a throttle adjustment signal; and

adjusting said speed of said variable speed energy generating device using said throttle adjustment signal, thereby adjusting an output power to a load.

20. The system according to claim 19, further comprising shedding a portion of said load based on said load shed term in response to a decrease in said speed and an increase in an output current.

21. The system according to claim 20, wherein said portion is a power margin of said variable speed energy generating device.

22. The system according to claim 20, further comprising shedding a portion of said load by decreasing an inverter AC output voltage.

23. The system according to claim 19, wherein said speed command is a percentage of engine performance for said variable speed energy generating device.

24. The system according to claim 19, further comprising a means for detecting steady state speed errors.