High efficiency power generating system

• US 4,964,027 A
• Filed: 12/05/1989
• Issued: 10/16/1990
• Est. Priority Date: 12/05/1989
• Status: Expired due to Fees

• Current Assignee: Sundstrand Corporation (Rtx Corporation)
• Original Assignee: Sundstrand Corporation (Rtx Corporation)
• Inventors: Cook, Alexander, Hitt, David H., Rice, John N.
• Primary Examiner(s): Wong, Peter S.
• Application Number:
  US07/446,430
• Time in Patent Office: 315 Days
• Field of Search: 363/39, 363/40, 363/44, 363/45, 363/46, 363/47, 363/48, 363/71, 363/78, 363/79, 363/81, 363/84, 363/95, 307/22, 307/26, 307/72
• US Class Current: 363/40
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output

Abstract

A power generating system (10) in accordance with the present invention includes a converter (14) for producing an AC output (16) including a fundamental and at least one harmonic of the fundamental; a frequency analyzer (18), having at least one input coupled to the AC output, for providing an analysis of a frequency spectrum of the AC output; a processor (36), coupled to the frequency analyzer, for calculating at least one switching frequency, each switching frequency being used for transforming a different harmonic within the AC output back to the fundamental; a controller (34), responsive to the at least one calculated switching frequency, for producing control signals at the at least one calculated frequency for transforming the at least one harmonic back to the fundamental; a separating filter (24), coupled to the AC output, for separating the fundamental and that at least one harmonic; at least one converter (30 and 32), coupled to the at least one harmonic from the converter and to the controller, each converter being switched by control signals from the controller which have a calculated switching frequency for transforming at least one of the at least one harmonic to the fundamental; and outputs from the at least one converter being combined with the fundamental from the separating filter.

Claims

1. A power generating system comprising:

a converter for producing an AC output including a fundamental and at least one harmonic of the fundamental in response to applied control signals;

a frequency analyzer, having at least one input coupled to the AC output, for providing an analysis of a frequency spectrum of the AC output;

a processor, coupled to the frequency analyzer, for calculating at least one switching frequency, each switching frequency being used for transforming a different harmonic within the AC output to the fundamental;

a controller, responsive to the at least one calculated switching frequency, for producing control signals at the at least one calculated switching frequency for transforming the at least one harmonic back to the fundamental and control signals for the converter for producing the AC output;

a separating filter, coupled to the AC output, for separating the AC output into the fundamental and the at least one harmonic;

at least one additional converter, coupled to the at least one harmonic from the converter and to the controller, each converter being switched by control signals from the controller which have a calculated switching frequency for transforming one of the at least one harmonics to the fundamental; and

outputs from the at least one converter being combined with the fundamental from the separating filter.

2. A power generating system in accordance with claim 1 wherein:

the frequency analyzer identifies harmonics which have a voltage above a threshold; and

the processor calculates at least one switching frequency with each switching frequency being a different harmonic having a voltage level above the threshold and each switching frequency Ws equal Wh plus Wa where Ws is equal to or less than 2*Wh, Wh equals a harmonic frequency and Wa equals the transformed fundamental frequency.

3. A power generating system in accordance with claim 1 further comprising:

a low pass filter, coupled to an output of each of the at least one additional converter, for attenuating harmonics above the fundamental with an output of the low pass filter being coupled to the fundamental produced by the separating filter.

4. A power generating system in accordance with claim 2 further comprising:

a low pass filter, coupled to an output of each of the at least one additional converter, for attenuating harmonics above the fundamental with an output of the low pass filter being coupled to the fundamental produced by the separating filter.

5. A power generating system in accordance with claim 1 further comprising:

a phase reference signal generator, coupled to the AC output from the converter, for producing a signal representative of a phase shift produced by the separating filter;

a phase comparator, coupled to the AC output produced by the separating filter and the signal representative of phase shift, for producing a phase error control signal proportional to a difference between the fundamental from the separating filter and the signal representative of phase shift; and

the controller is responsive to the phase error control signal for varying the control signals to change phase of an output produced by one of the converters so that the fundamental from the separating filter is in phase with the output of each of the at least one additional converters.

6. A power generating system in accordance with claim 5 wherein:

the one of the converters is the converter for producing an AC output.

7. A power generating system in accordance with claim 5 wherein:

the one of the converters is the at least one additional converter.

8. A power generating system in accordance with claim 2 further comprising:

a phase reference signal generator coupled to the AC output from the converter, for producing a signal representative of a phase shift produced by the separating filter;

a phase comparator, coupled to the AC output produced by the separating filter and the signal representative of phase shift, for producing a phase error control signal proportional to a difference between the fundamental from the separating filter and the signal representative of phase shift; and

the controller is responsive to the phase error control signal for varying the control signals to change phase of an output produced by one of the converters so that the fundamental from the separating filter is in phase with the output of each of the at least one additional converters.

9. A power generating system in accordance with claim 8 wherein:

the one of the converters is the converter for producing an AC output.

10. A power generating system in accordance with claim 8 wherein:

the one of the converters is the converter for producing an AC output.

11. A power generating system in accordance with claim 3 further comprising:

a phase reference signal generator coupled to the AC output from the converter, for producing a signal representative of a phase shift produced by the separating filter;

a phase comparator, coupled to the AC output produced by the separating filter and the signal representative of phase shift, for producing a phase error control signal proportional to a difference between the fundamental from the separating filter and the signal representative of phase shift; and

the controller is responsive to the phase error control signal for varying the control signals to change phase of an output produced by one of the converters so that the fundamental from the separating filter is in phase with the output of each of the at least one additional converters.

12. A power generating system in accordance with claim 11 wherein:

the one of the converters is the converter for producing an AC output.

13. A power generating system in accordance with claim 11 wherein:

the one of the converters is the at least one additional converter.

14. A power generating system in accordance with claim 4 further comprising:

a phase reference signal generator coupled to the AC output from the converter, for producing a signal representative of a phase shift produced by the separating filter;

a phase comparator, coupled to the AC output produced by the separating filter and the signal representative of phase shift, for producing a phase error control signal proportional to a difference between the fundamental from the separating filter and the signal representative of phase shift; and

the controller is responsive to the phase error control signal for varying the control signals to change phase of an output produced by one of the converters so that the fundamental from the separating filter is in phase with the output of each of the at least one additional converters.

15. A power generating system in accordance with claim 14 wherein:

the one of the converters is the converter for producing an AC output.

16. A power generating system in accordance with claim 14 wherein:

the one of the converters is the at least one additional converter.

17. A DC power generating system comprising:

a converter for producing an AC output;

a transformer, coupled to the AC output, for producing a transformed AC output having a voltage different than the AC output of the converter;

a frequency analyzer, having at least one input coupled to the AC output of the transformer, for providing an analysis of a frequency spectrum of one of the AC outputs;

a processor, coupled to the frequency analyzer, for calculating at least one switching frequency, each switching frequency being used for transforming a different frequency component within the AC output back to DC;

a controller, responsive to the at least one calculated switching frequency, for producing control signals at the at least one calculated switching frequency for transforming at least one frequency component back to DC;

a separating filter, coupled to the AC output, for separating the AC output into DC and the at least one frequency component;

at least one additional converter, coupled to the at least one frequency component from the converter and to the controller, each converter being switched by control signals from the controller which have a calculated switching frequency for transforming one of the at least one frequency components to DC; and

outputs from the at least one converter being combined with the DC from the separating filter.

18. A power generating system in accordance with claim 17 wherein:

the frequency analyzer identifies frequency components which have a voltage above a threshold; and

the processor calculates at least one switching frequency with each switching frequency for a frequency component having a voltage level above the threshold and each switching frequency Ws equals Wh plus Wa where Ws is equal to or less than 2*Wh, Wh equals a frequency component and WA is zero.

19. A power generating system in accordance with claim 17 further comprising:

a low pass filter, coupled to an output of each of the at least one additional converter, for attenuating AC components with an output of the low pass filter being coupled to the DC produced by the separating filter.

20. A power generating system in accordance with claim 18 further comprising:

a low pass filter, coupled to an output of each of the at least one additional converter, for attenuating AC components with an output of the low pass filter being coupled to the DC produced by the separating filter.

21. A method of power generation of AC at a fundamental frequency comprising:

switching a DC potential to generate an AC output including a fundamental and at least one harmonic of the fundamental;

analyzing a frequency spectrum of the AC output to detect at least one harmonic which is above a threshold voltage;

calculating at least one switching frequency with each switching frequency being used for transforming a separate harmonic of the at least one harmonic to the fundamental; and

separating the at least one harmonic of the fundamental from the fundamental and switching at least one separated harmonic of the fundamental at least one calculated switching frequency to transform at least one harmonic to the fundamental.

22. A method in accordance with claim 21 further comprising:

low pass filtering the transformed fundamental for attenuating harmonics within the transformed fundamental prior to combining the transformed fundamental with the fundamental and each switching frequency Ws equals Wh plus Wa where WS is equal to or less than 2*Wh;

Wh equals a harmonic frequency and Wa equals a transformed frequency.

23. A method in accordance with claim 21 further comprising:

modifying the switching of the at least harmonic in response to a phase error control signal which is a function of a difference between a phase shift produced by separating the fundamental and the at least one harmonic and the fundamental produced by separation to cause the transformed fundamental to have a phase which matches a phase of the fundamental produced by separation.

24. A method in accordance with claim 22 further comprising:

low pass filtering the transformed fundamental for attenuating harmonics within the transformed fundamental prior to combining the transformed fundamental with the fundamental and each switching frequency Ws equals Wh plus Wa where WS is equal to or less than 2*Wh;

Wh equals a harmonic frequency and Wa equals transformed frequency.

25. A method of power generation of DC comprising:

switching a DC potential to generate an AC output having a first voltage;

transforming the AC output of the first voltage to produce an AC output of a second voltage;

analyzing a frequency spectrum of one of the AC outputs to detect an AC component which is above a threshold voltage;

calculating at least one switching frequency with each switching frequency being used for transforming a separate frequency component to DC;

producing DC from the AC output of the second voltage; and

separating at least one frequency component from the DC and switching at least one separate frequency component at at least one calculated switching frequency to transform at least one frequency component to DC.

26. A method in accordance with claim 25 further comprising:

low pass filtering the transformed DC for attenuating any frequency components within the transformed DC prior to combining the transformed DC with the DC produced from the AC output of the second voltage; and

each switching frequency Ws equals Wh plus Wa where Ws is equal to or less than 2*Wh, Wh equals a frequency component and Wa is zero.

27. A hybrid power generating system comprising:

an AC power generating unit including;

(a) a converter for producing an AC output including a fundamental and at least one harmonic of the fundamental in response to applied control signals;

(b) a frequency analyzer, having at least one input coupled to the AC output, for providing an analysis of a frequency spectrum of the AC output;

(c) a processor, coupled to the frequency analyzer, for calculating at least one switching frequency, each switching frequency being used for transforming a harmonic within the AC output back to the fundamental;

(d) a controller, responsive to the at least one switching frequency, for producing control signals for transforming the at least one switching frequency back to the fundamental and control signals for the converter for producing the AC output;

(e) a first separating filter, coupled to the AC output, for separating the AC output into the fundamental and the at least one harmonic;

(f) at least one additional converter, coupled to the at least one harmonic from the converter and to the controller, each converter being switched by control signals from the controller which have a switching frequency for transforming one of the at least one harmonics to the fundamental; and

(g) outputs from the at least one converter being combined with the fundamental from the first separating filter;

a DC power generating unit including;

(a) a converter for producing an AC output;

(b) a transformer, coupled to the AC output, for producing a transformed AC output having a voltage different than the AC output of the inverter;

(c) a frequency analyzer, having at least one input coupled to the AC output from the transformer, for providing an analysis of a frequency spectrum of one of the AC outputs;

(d) a processor, coupled to the frequency analyzer, for calculating at least one switching frequency, each switching frequency being used for transforming a different frequency component within the AC output back to DC;

(e) a controller, responsive to the at least one switching frequency, for producing control signals for transforming at least one frequency component back to DC;

(f) a second separating filter, coupled to the AC output, for separating the AC output into the DC and the at least one frequency component;

(g) at least one additional converter, coupled to the at least one frequency component from the converter and to the controller, each converter being switched by control signals from the controller which have a switching frequency for transforming one of the at least one frequency components to DC; and

(h) outputs from the at least one converter being combined with the DC from the second separating filter; and

a power generation system controller for controlling generation of electrical power by the power generating units.

28. A hybrid power generating system in accordance with claim 27 wherein:

in the AC power generating unit the frequency analyzer identifies harmonics which have a voltage above a threshold;

the processor calculates a switching frequency for at least one harmonic having a voltage level above the threshold; and

a low pass filter is coupled to an output of each of the at least one additional converter for attenuating harmonics above the fundamental with an output of the low pass filter being coupled to the fundamental produced by the first separating filter; and

each switching frequency Ws equals Wh plus Wa where Ws is equal to or less than 2*Wh, Wh equals a harmonic frequency and Wa equals the transformed fundamental frequency; and

in the DC power generating unit a low pass filter is coupled to an output of each of the at least one additional converter for attenuating AC components with an output of the low pass filter being coupled to the DC produced by the separating filter; and

each switching frequency Ws equals Wh plus Wa where Ws is equal to or less than 2*Wh, Wh equals a frequency component and Wa is zero.

29. A hybrid power generating system in accordance with claim 27 further comprising:

a phase reference signal generator, coupled to the AC output from the separating filter, for producing a signal representative of a phase shift produced by the separating filter;

a phase comparator, coupled to the AC output produced by the separating filter, and the signal representative of phase shift, for producing phase error control signal proportional to a difference between the fundamental from the separating filter and the signal representation of phase shift; and

the controller of the AC power generating unit is responsive to the phase error control signal for varying the control signals to change phase of an output produced by one of the converters so that the fundamental from the first separating filter is in phase with the output of each of the at least one additional converters of the AC power generating unit.

30. A hybrid power generating system in accordance with claim 28 further comprising:

a phase reference signal generator, coupled to the AC output from the first separating filter, for producing a signal representative of a phase shift produced by the first separating filter;

a phase comparator, coupled to the AC output produced by the separating filter, and the signal representative of phase shift, for producing phase error control signal proportional to a difference between the fundamental from the separating filter and the signal representation of phase shift; and

the controller is responsive to the phase error control signal for varying the control signals to change phase of an output produced by one of the converters of the AC power generating unit so that the fundamental from the first separating filter is in phase with the output of each of the at least one additional converters of the AC power generating unit.

31. A hybrid power generating system in accordance with claim 29, wherein:

the one of the converters is the converter for producing an AC output.

32. A hybrid power generating system in accordance with claim 29 wherein:

the one of the converters is the at least one additional converter.

33. A hybrid power generating system in accordance with claim 30 wherein:

the one of the converters is the converter for producing an AC output.

34. A hybrid power generating system in accordance with claim 30 wherein:

the one of the converters is the at least one additional converter.