Reconfigurable power systems and converters

• US 9,537,319 B2
• Filed: 03/29/2012
• Issued: 01/03/2017
• Est. Priority Date: 04/15/2011
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited), North Carolina State University (University of North Carolina System)
• Original Assignee: ABB Research Ltd. (ABB Limited), North Carolina State University (University of North Carolina System)
• Inventors: Parkhideh, Babak, Kim, Hongrae
• Primary Examiner(s): Fureman, Jared
• Assistant Examiner(s): Dominique, Emmanuel R
• Application Number:
  US13/433,357
• Publication Number:
  US 20120261999A1
• Time in Patent Office: 1,741 Days
• Field of Search: 307/80, 363/95, 363/106
• US Class Current: 1/1
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

Reconfigurable power systems and converters and operating methods therefor are disclosed. Reconfigurable power systems may include a DC power source, an electrical energy storage device, an AC power grid connection, and a power converter configured to selectively couple two or more of the DC power source, the electrical energy storage device, and the AC power grid connection.

Claims

1. A reconfigurable power system, comprising:

a DC power source;

an electrical energy storage device;

an AC power grid connection; and

a power converter comprising;

a plurality of switching devices,

a first switch interposed between said electrical energy storage device and said plurality of switching devices,

a second switch interposed between said electrical energy storage device and said AC power grid connection,

a third switch interposed between said AC power grid connection and said plurality of switching devices, and

a fourth switch interposed between said DC power source and said plurality of switching devices,

said power converter configured to

selectively couple the DC power source to the electrical energy storage device by closing said fourth switch and maintaining either;

said first switch in an open position and said second switch in a closed position;

or said first switch in a closed position and said second switch in an open position,

selectively couple the DC power source to the AC power grid connection by maintaining said second switch in an open position, and said third and fourth switches in a closed position, and

selectively couple the electrical energy storage device to the AC power grid connection by maintaining said first and third switches in a closed position,

and wherein the power converter is further configured to;

(1) deliver, during a first time period, power from the DC power source to the electrical energy source but not to the AC power grid connection, the first time period including at least a portion of time in which power outputted by the DC power source is around a power source peak level and a grid demand level of an external AC power grid that is coupled to the reconfigurable power system via the AC power grid connection is below a peak demand level;

(2) deliver, during a second time period, power from the DC power source and the electrical energy source to at least the AC power grid connection, the second time period including at least a portion of time in which the grid demand level is around the peak demand level; and

(3) deliver, during a third time period, power from the electrical energy storage device to the AC power grid connection, the third time period including at least a portion of time in which the power outputted by the DC power source is less than the source peak level and the grid demand level is below the peak demand level.

2. The reconfigurable power system of claim 1, wherein the DC power source includes at least one solar cell.

3. The reconfigurable power system of claim 1, wherein the electrical energy storage device includes a battery.

4. The reconfigurable power system of claim 1, wherein said plurality of switching devices includes at least one semiconductor switching device selected from the group consisting of a power transistor, a power MOSFET, an insulated gate bipolar transistor and a gate turn-off thyristor.

5. The reconfigurable power system of claim 1, wherein said plurality of switching devices are configured to selectively function as a DC-AC inverter, a DC-DC converter, or an AC-DC converter.

6. The reconfigurable power system of claim 5, wherein said plurality of switching devices are configured to function as the DC-AC inverter when coupling at least one of the DC power source and the electrical energy storage device to the AC power grid connection to deliver power from at least one of the DC power source and the electrical energy storage device to an AC power grid.

7. The reconfigurable power system of claim 5, wherein said plurality of switching devices are configured to function as the DC-DC converter when coupling the DC power source to the electrical energy storage device to charge the electrical energy storage device.

8. The reconfigurable power system of claim 5, wherein said plurality of switching devices are configured to function as the AC-DC converter when coupling the AC power grid connection to the electrical energy storage device to charge the electrical energy storage device.

9. The reconfigurable power system of claim 1, wherein:

the reconfigurable power system is configured to operate in a selected one of at least three modes;

in a first one of the modes said plurality of switching devices are configured as a DC-DC converter coupling the DC power source to the electrical energy storage device;

in a second one of the modes said plurality of switching devices are configured as a DC-AC inverter coupling at least one of the DC power source and the electrical energy storage device to the AC power grid connection; and

in a third one of the modes said plurality of switching devices are configured as an AC-DC converter coupling the AC power grid connection to the electrical energy storage device.

10. The reconfigurable power system of claim 1, wherein:

the reconfigurable power system is configured to operate in a selected one of at least three modes;

in a first one of the modes said plurality of switching devices are configured as a DC-DC converter coupling the DC power source to the electrical energy storage device;

in a second one said plurality of switching devices are configured as a DC-AC inverter coupling the DC power source and the electrical energy storage device to the AC power grid connection; and

in a third one of the modes said plurality of switching devices are configured as a DC-AC inverter coupling the electrical energy storage device to the AC power grid connection.

11. The reconfigurable power system of claim 10, where in a fourth one of the at least three modes said plurality of switching devices are configured as a DC-AC inverter coupling the DC power source to the AC power grid connection.

12. The reconfigurable power system of claim 10, comprising:

a capacitor connected in parallel with the electrical energy storage device and the DC power source; and

a resistor configured to selectively series-couple the electrical energy storage device to the capacitor.

13. A reconfigurable power converter, comprising:

a power source connection configured to couple with a DC power source;

a storage device connection configured to couple with an electrical energy storage device;

a grid connection configured to couple with an AC power grid; and

a power converter comprising a plurality of switching devices and a plurality of switches, said plurality of switches are selectively interposed between said plurality of switching devices and said power source connection, said storage device connection and said grid connection, said power converter configured to selectively couple two or more of the power source connection, the storage device connection, and the grid connection, wherein the power converter is selectively configured as one of;

a DC-DC converter when coupling the power source connection to the storage device connection, but not to the grid connection, by closing selected switches in said plurality of switches and routing, during a first time period, power from said DC power source through said selected switches that are closed and said plurality of switching devices to said electrical energy storage device, said first time period including at least a portion of time in which power outputted by the DC power source is around a power source peak level and a grid demand level of an external AC power grid that is coupled to the reconfigurable power system via the grid connection is below a peak demand level;

a DC-AC inverter when coupling, during a second time period, at least one of the power source connection and the storage device connection to the grid connection by closing selected switches in said plurality of switches and routing power from one of said DC power source and said electrical energy storage device through said selected switches that are closed and said plurality of switching devices to said AC power grid, the second time period including at least a portion of time in which the grid demand level is around the peak demand level; and

an AC-DC converter when coupling, during a third time period, the grid connection to the storage device connection by closing selected switches in said plurality of switches and routing power from said AC power grid through said selected switches that are closed and said plurality of switching devices to said electrical energy storage device.

14. The reconfigurable power converter of claim 13, wherein the DC power source includes at least one solar cell.

15. The reconfigurable power converter of claim 13, wherein the electrical energy storage device includes a battery.

16. The reconfigurable power converter of claim 13, wherein said plurality of switching devices includes at least one semiconductor switching device.

17. The reconfigurable power converter of claim 13, comprising a resistor configured to selectively limit inrush current to an electrical energy storage device coupled with the storage device connection.

18. A method of operating a reconfigurable power converter configured to selectively couple two or more of a DC power source, an electrical energy storage device, and an AC power grid connection, wherein the power converter comprises a plurality of switching devices and a plurality of switches interposed between the DC power source, the electrical energy storage device, and the AC power grid connection, and the method comprises:

configuring, during a first time period, the power converter as a DC-DC converter and coupling the DC power source to the electrical energy storage device by closing selected switches in said plurality of switches and routing power from said DC power source through said selected switches that are closed and said plurality of switching devices to said electrical energy storage device, the first time period including at least a portion of time in which power outputted by the DC power source is around a power source peak level and a grid demand level of an external AC power grid that is coupled to the reconfigurable power system via the AC power grid connection is below a peak demand level;

configuring, during a second time period, the power converter as a DC-AC inverter and coupling at least one of the DC power source and the electrical energy storage device to the AC power grid connection by closing selected switches in said plurality of switches and routing power from one of said DC power source and said electrical energy storage device through said selected switches that are closed and said plurality of switching devices to said AC power grid connection, the second time period including at least a portion of time in which the grid demand level is around the peak demand level; and

configuring, during a third time period, the power converter as a DC-AC inverter and coupling the electrical energy storage device to the AC power grid connection by closing selected switches in said plurality of switches and routing power from said electrical energy storage device through said selected switches that are closed and said plurality of switching devices to said AC power grid connection, the third time period including at least a portion of time in which the power outputted by the DC power source is less than the source peak level and the grid demand level is below the peak demand level.

19. The method of claim 18, wherein the DC power source includes at least one solar cell.

20. The method of claim 19, wherein the power converter performs maximum power point tracking for the at least one solar cell when the power converter is configured as a DC-DC converter that couples the DC power source to the electrical energy storage device.

21. The method of claim 19, comprising configuring the power converter as a DC-AC inverter and coupling the DC power source to the AC power grid connection, wherein the power converter performs maximum power point tracking for the at least one solar cell when the power converter is configured as a DC-AC inverter that couples the DC power source to the AC power grid connection.

22. The method of claim 18, comprising configuring the power converter as an AC-DC converter and coupling the AC power grid connection to the electrical energy storage device by closing selected switches in said plurality of switches and routing power from said AC power grid connection through said selected switches that are closed and said plurality of switching devices to said electrical energy storage device.

23. The method of claim 18, wherein a capacitor is connected in parallel with the electrical energy storage device, the method comprising:

uncoupling the DC power source from the electrical energy storage device;

equalizing a voltage of the electrical energy storage device to a voltage of the capacitor; and

configuring the power converter as a DC-AC inverter and coupling the DC power source and the electrical energy storage device to the AC power grid connection after equalizing the voltage of the electrical energy storage device to the voltage of the capacitor.

24. The method of claim 23, where equalizing the voltage of the electrical energy storage device to the voltage of the capacitor comprises connecting the electrical energy storage device to the capacitor through a resistor.