Electric starter generator system employing bidirectional buck-boost power converters, and methods therefor

• US 7,327,113 B2
• Filed: 11/15/2004
• Issued: 02/05/2008
• Est. Priority Date: 11/15/2004
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Bringman, Matthew Christopher, Steigerwald, Robert Louis, Garces, Luis Jose
• Primary Examiner(s): DUDA, RINA I
• Application Number:
  US10/990,193
• Publication Number:
  US 20060103341A1
• Time in Patent Office: 1,177 Days
• Field of Search: 318/599, 318/811, 318/727, 318/801, 363/17, 363/21.1, 363/22, 363/26, 290/40.C, 290/4.C, 290/40.B
• US Class Current: 318/599
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

A bidirectional buck-boost power converter 13 including a pair of inverter modules 14, 15 disposed at an output of a machine, and an inductor L_o connected between the pair of inverter modules 14, 15. A method for controlling a voltage output of a machine starter generator having an inverter rectifier and bidirectional buck-boost converter, includes outputting a dc voltage controlled by bidirectional buck-boost pulse width modulation (PWM) switching control, when the starter generator is in a generator mode.

Claims

1. An electric starter generator (ESG) system configured to supply mechanical power to a turbine during a starting operation and configured to transform mechanical power from the turbine to electrical power during a generating operation, said ESG system comprising:

a synchronous starter generator mechanically coupled to the turbine and configured to supply an alternating current (AC) voltage;

an inverter/rectifier electrically connected to said synchronous starter generator and configured to convert the AC voltage to a DC voltage; and

a bidirectional buck-boost power converter configured to perform each of a plurality of operations;

step up the output voltage during transient operations, step down the output voltage during transient operations, step up the output voltage during steady state operations, and step down the output voltage during steady state operations, such that a DC bus voltage is maintained substantially constant during both steady state and transient operations solely via the bidirectional buck-boost power converter and one or more DC bus link filters.

2. The ESG system of claim 1, wherein said bidirectional buck-boost power converter comprises:

a pair of half bridge inverter modules disposed at an output of said inverter/rectifier; and

an inductor connected between said pair of half bridge inverter modules.

3. The ESG system of claim 1, wherein said inverter/rectifier is configured for operation in a six-step mode.

4. The ESG system of claim 3, wherein said inverter/rectifier is configured for operation in the six-step mode during a starting operation of the synchronous starter generator.

5. The ESG system of claim 1, wherein said inverter/rectifier is configured for operation in a pulse width modulation (PWM) mode.

6. The ESG system of claim 4, wherein said inverter/rectifiers is configured for operation in the PWM mode to deliver a DC link voltage proportional to a machine frequency of the synchronous starter generator during a starting operation.

7. The ESG system of claim 1, wherein said bidirectional buck-boost power converter is configured to maintain an output voltage within a tolerance of at least +22% and −

26% during the transient operation.

8. The ESG system of claim 1, wherein said bidirectional buck-boost power converter comprises:

a pair of full-bridge inverter modules disposed at an output of said inverter/rectifier; and

a transformer connected between said pair of full-bridge inverter modules.

9. A method for controlling a voltage output of a wound field synchronous starter generator having an inverter/rectifier and a bi-directional buck-boost converter, said method comprising:

outputting a DC voltage based upon a field current when said wound field synchronous starter generator is in a generator mode; and

performing a buck-boost operation of the buck-boost converter in a mode selected from a buck-boost converter conduction mode, a buck-boost converter load application mode, a buck-boost converter load rejection mode and a buck-boost converter starting mode such that a DC bus voltage is maintained substantially constant solely via the bi-directional buck-boost converter and one or more DC bus link filters during the conduction mode, the load application mode, the load rejection mode and the starting mode.

10. A method for controlling a voltage output of an ac starter generator having an inverter/rectifier and bi-directional buck-boost converter, said method comprising;

outputting a dc voltage controlled by a bi-directional buck-boost pulse width modulation (PWM) switching control, when said ac starter generator is in a generator mode, such that a dc bus voltage is maintained substantially constant solely via the bi-directional buck-boost converter and one or more DC bus link filters during a sudden load application or removal.

11. The method of claim 10, wherein only a plurality of inverter/rectifier diodes conduct a current to an output of said ac starter generator.

12. The method of claim 10, wherein said inverter/rectifier performs PWM switching to perform at least one of drawing sinusoidal current waves from said ac starter generator and boosting said dc voltage to said bi-directional buck-boost converter.

13. The method of claim 10, further comprising:

controlling said voltage output and an output current based upon inverter PWM control, when said an starter generator is in a start mode.

14. The method of claim 13, wherein only a plurality of inverter/rectifier diodes conduct said current to an output of said an starter generator.

15. The method of claim 13, wherein said bi-directional buck-boost converter performs PWM switching to control a current from a DC bus to said inverter/rectifier.

16. The method of claim 10, further comprising:

operating said inverter/rectifier in six-step mode, when said ac starter generator is in a start mode.

17. The method of claim 16, further comprising:

controlling said output voltage by PWM switching of said bi-directional buck-boost converter.

18. The method of claim 16, wherein said output voltage is proportional to a machine speed of said ac starter generator.