Expandable hybrid electric generator and method therefor

• US 6,362,540 B1
• Filed: 10/20/1999
• Issued: 03/26/2002
• Est. Priority Date: 10/20/1999
• Status: Expired due to Term

• Current Assignee: Pinnacle West Capital Corporation
• Original Assignee: Pinnacle West Capital Corporation
• Inventors: Hill, Bryan T.
• Primary Examiner(s): Ballato, Josie
• Assistant Examiner(s): POLK, SHARON A
• Application Number:
  US09/422,137
• Time in Patent Office: 888 Days
• Field of Search: 307/52-63, 307/31-35, 307/24, 307/66, 340/310, 363/71, 363/127
• US Class Current: 307/52
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy wind motors F03D
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/40 Synchronising a generator for connection to a network or to another generator
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects

Abstract

An expandable hybrid electric generator (20) includes a number of power blocks (22) that may be nearly identical to one another. The power blocks (22) are controlled by a master controller (34), and an external supervisor (30) performs some master controller (34) functions should the master controller (34) fault. The power blocks (22) each include a battery bank (42) and an inverter/charger (44), both of which couple to a DC bus (40). The inverter (44) and an AC generator (50) couple to an AC bus (24). The DC busses (40) of the power blocks (22) remain independent of one another, but all power blocks (22) couple together at the AC bus (24). The master controller (34) issues instructions to the inverters (44) that maintain approximately equal states at the independent DC busses (40) of the power blocks (22).

Claims

1. An expandable hybrid electric power generating system comprising:

an AC bus configured to supply electrical power to an electrical load;

a plurality of power blocks wherein each of said power blocks has a DC energy source coupled to a DC bus of said power block, and an inverter coupled to said DC bus of said power block and to said AC bus; and

a controller in communication with said power blocks, said controller being configured to provide instructions to said power blocks which cause said power blocks to maintain approximately equal states at said DC busses of said power blocks.

2. An expandable hybrid electric power generating system as claimed in claim 1 wherein:

said DC energy source in each of said power blocks includes a battery;

said inverters of said power blocks are configured to selectively transfer power from said AC bus to said DC busses of said power blocks and to transfer power from said DC busses of said power blocks to said AC bus;

said controller is configured to determine, when said inverters are transferring power from said DC busses to said AC bus, if a difference between an electrical load share for one of said power blocks and an average electrical load share for all of said power blocks is greater than a first predetermined amount, and to disable one of said power blocks from supplying power to said AC bus if said load share difference is greater than said first predetermined amount;

said controller is further configured to determine, when said inverters are transferring power from said AC bus to said DC busses, if a difference between an electrical charge share for one of said power blocks and an average electrical charge share for all of said power blocks is greater than a second predetermined amount, and to disable one of said power blocks from supplying power to said AC bus if said charge share difference is greater than said second predetermined amount; and

said controller is further configured to equalize said battery of one of said plurality of power blocks using electrical power supplied from said others of said power blocks.

3. An expandable hybrid electric power generating system as claimed in claim 2 additionally comprising:

an external supervisor in communication with said plurality of power blocks, said external supervisor being configured to respond to a power outage at said AC bus which exceeds a predetermined duration by controlling operation of said plurality of power blocks;

a first power supply for energizing said controller; and

a second power supply for energizing said external supervisor.

4. An expandable hybrid electric power generating system as claimed in claim 1 additionally comprising an AC generator located in each of said plurality of power blocks, said AC generators being coupled to said AC bus.

5. An expandable hybrid electric power generating system comprising:

an AC bus configured to supply electrical power to an electrical load;

a first power block having a first DC energy source coupled to a first DC bus, a first inverter coupled to said first DC bus and to said AC bus, and a generator coupled to said AC bus;

a second power block having a second DC energy source coupled to a second DC bus, and a second inverter coupled to said second DC bus and to said AC bus; and

a controller in signal communication with said first and second DC busses and said first and second inverters, said controller being configured to maintain approximately equal states at said first and second DC busses.

6. An expandable hybrid electric power generating system as claimed in claim 5 additionally comprising a plurality of DC energy sources coupled to one of said first and second DC busses.

7. An expandable hybrid electric power generating system as claimed in claim 5 wherein:

said system additionally comprises a third power block having a third DC energy source coupled to a third DC bus, and a third inverter coupled to said third DC bus and to said AC bus;

said controller is in signal communication with said third DC bus and said third inverter; and

said controller is configured to maintain approximately equal states among said first, second and third DC busses.

8. An expandable hybrid electric power generating system as claimed in claim 5 wherein:

said controller is configured to determine if a difference between an electrical load share for one of said power blocks and an average electrical load share for all of said power blocks is greater than a predetermined amount; and

said controller is further configured to activate an alarm if said difference is greater than said predetermined amount.

9. An expandable hybrid electric power generating system as claimed in claim 5 wherein:

said controller is configured to determine if a difference between an electrical load share for one of said power blocks and an average electrical load share for all of said power blocks is greater than a predetermined amount; and

said controller is further configured to disable said one power block from supplying power to said AC bus if said difference is greater than said predetermined amount.

10. An expandable hybrid electric power generating system as claimed in claim 5 wherein:

said controller is configured to monitor said electrical load; and

said controller is configured to control enabled and disabled states of said generator for supplying power to said AC bus in response to said electrical load.

11. An expandable hybrid electric power generating system as claimed in claim 10 wherein:

said generator is a first generator;

said second power block has a second generator coupled to said AC bus;

said controller is configured so that when said electrical load is less than a first threshold, neither of said first and second generators is enabled to supply power to said AC bus;

said controller is configured so that when said electrical load is greater than said first threshold and less than a second threshold, one of said first and second generators is enabled to supply power to said AC bus; and

said controller is configured so that when said electrical load is greater than said second threshold, both of said first and second generators are enabled to supply power to said AC bus.

12. An expandable hybrid electric power generating system as claimed in claim 11 wherein:

said first and second inverters are configured to permit power flow from said respective first and second DC busses to said AC bus for supplying power to said electrical load and to permit power flow from said AC bus to said respective first and second DC busses for charging said first and second DC energy sources; and

said first and second thresholds are different values when power flows from said first and second DC busses to said AC bus than when power flows from said AC bus to said first and second DC busses.

13. An expandable hybrid electric power generating system as claimed in claim 5 wherein:

said controller receives signals indicating instantaneous voltages on said first DC bus and on said second DC bus; and

said controller is configured to filter said signals so that said first and second DC busses are maintained at approximately equal states in response to filtered instantaneous voltage states of said first and second DC busses.

14. An expandable hybrid electric power generating system as claimed in claim 5 wherein said first and second inverters are configured to adjust power flow from said respective first and second DC busses to said AC bus independent of said electrical load and in response to commands issued by said controller to maintain approximately equal states at said first and second DC busses.

15. An expandable hybrid electric power generating system as claimed in claim 5 wherein said first and second inverters are configured to transfer power from said AC bus to said respective first and second DC busses to charge said first and second DC energy sources.

16. An expandable hybrid electric power generating system as claimed in claim 15 wherein:

said first DC energy source is a battery; and

said controller is configured to equalize said battery using electrical power supplied from said second power block.

17. An expandable hybrid electric power generating system as claimed in claim 15 wherein said first and second inverters are configured to adjust power flow from said AC bus to said first and second DC busses independent of loads on said first and second DC busses and in response to commands issued by said controller to maintain approximately equal states at said first and second DC busses.

18. An expandable hybrid electric power generating system as claimed in claim 17 wherein:

said controller is configured to determine if a difference between a charging share of one of said power blocks and an average charging share for all of said power blocks is greater than a predetermined amount; and

said controller is further configured to activate an alarm if said difference is greater than said predetermined amount.

19. An expandable hybrid electric power generating system as claimed in claim 17 wherein:

said controller is configured to determine if a difference between a charging share of one of said power blocks and an average charging share for all of said power blocks is greater than a predetermined amount; and

said controller is further configured to disable said one power block from supplying power to said AC bus if said difference is greater than said predetermined amount.

20. An expandable hybrid electric power generating system as claimed in claim 19 wherein said controller is configured to disable said one power block if said charging share is greater than said predetermined amount during a charging cycle but refrains from disabling said power block due to greater charging share during an absorbing cycle.

21. An expandable hybrid electric power generating system as claimed in claim 5 additionally comprising an external supervisor in communication with said first and second power blocks, said external supervisor being configured to respond to a power outage at said AC bus which exceeds a predetermined duration by controlling operation of said first and second power blocks.

22. An expandable hybrid electric power generating system as claimed in claim 5 additionally comprising an external supervisor in communication with said controller, said external supervisor being configured to control operation of said power blocks in response to a fault in said controller.

23. An expandable hybrid electric power generating system as claimed in claim 22 additionally comprising:

a first power supply for energizing said controller; and

a second power supply for energizing said external supervisor.

24. An expandable hybrid electric power generating system as claimed in claim 22 wherein said external supervisor is configured to disable said first and second power blocks from supplying power to said AC bus when said fault in said controller occurs.

25. An expandable hybrid electric power generating system as claimed in claim 24 wherein said external supervisor is configured to enable said first and second generators to provide power to said AC bus after disabling said first and second power blocks from supplying power to said AC bus.

26. A method of controlling an expandable hybrid electric power generating system having an AC bus configured to supply electrical power to an electrical load and a plurality of modular power blocks, wherein power block has a DC energy source coupled to a DC bus for that power block, and an inverter coupled to said DC bus and to said AC bus, and said method comprises:

receiving, at a controller, monitoring signals which describe states of said DC busses in said power blocks; and

sending adjustment instructions to said plurality of power blocks from said controller, said adjustment instructions being configured to maintain approximately equal states at said DC busses in said power blocks.

27. A method as claimed in claim 26 additionally comprising:

determining if a difference between an electrical load share for one of said power blocks and an average electrical load share for all of said power blocks is greater than a predetermined amount; and

activating an alarm if said difference is greater than said predetermined amount.

28. A method as claimed in claim 26 additionally comprising:

determining if a difference between an electrical load share for one of said power blocks and an average electrical load share for all of said power blocks is greater than a predetermined amount; and

disabling said one power block from supplying power to said AC bus if said difference is greater than said predetermined amount.

29. A method as claimed in claim 26 wherein each of said power blocks additionally has an AC generator coupled to said AC bus, said method additionally comprising:

monitoring said electrical load; and

controlling enabled and disabled states of said first and second generators for supplying power to said AC bus in response to said electrical load.

30. A method as claimed in claim 26 wherein:

said electrical load undergoes instantaneous changes; and

said adjustment instructions are substantially non-responsive to said instantaneous changes.

31. A method as claimed in claim 26 wherein:

said DC energy sources of said power blocks are batteries;

said inverters of said plurality of power blocks are configured to selectively transfer power from said AC bus to respective DC busses of said power blocks to charge said respective batteries of said power blocks; and

said method additionally comprises equalizing one of said batteries of said plurality of power blocks using electrical power supplied from others of said power blocks.

32. A method as claimed in claim 26 wherein:

said inverters of said plurality of power blocks are configured to selectively transfer power from said AC bus to respective DC busses of said power blocks to charge said respective DC energy sources of said power blocks;

said sending activity maintains approximately equal states at said DC busses of said power blocks while power flows from said DC busses to said AC bus; and

said method additionally comprises sending charging adjustment instructions to said plurality of power blocks, said charging adjustment instructions being configured to maintain approximately equal states at said DC busses in said power blocks while power flows from said AC bus to said DC busses.