POWER CONVERSION SYSTEM

• US 20140167661A1
• Filed: 02/21/2014
• Published: 06/19/2014
• Est. Priority Date: 08/22/2011
• Status: Active Grant

• Current Assignee: Franklin Electric Company Incorporated (EBW, Inc.)
• Original Assignee: Franklin Electric Company Incorporated (EBW, Inc.)
• Inventors: van der Merwe, Lyon
• Granted Patent: US 9,479,070 B2
• Time in Patent Office: Days
• US Class Current: 318/400.3
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

This disclosure relates to a power conversion system to power a variable impedance load with a variable power source, the power conversion system comprising a power converter including input terminals adapted to receive variable power from the variable power source and output terminals providing a converted power to the variable impedance load based on the variable power received at the input terminals. The power converter increases the input voltage to an output voltage. The power converter is configured to reflect a source impedance of the variable power source to the variable impedance load.

Claims

1. A power conversion system comprising:

an input terminal adapted to receive variable power having an input voltage from a variable power source having a source impedance;

an output terminal adapted to provide converted power having an output voltage to a variable impedance load, the variable impedance load receiving a load voltage based on the output voltage;

a power converter including a switching controller, power switches controlled by the switching controller, a transformer coupled to the power switches, a rectification circuit configured to rectify an alternating current output from the transformer, and input and output capacitors, the switching controller configured to switch the power switches in an alternating unregulated manner to increase the input voltage to the output voltage, the power converter configured to reflect the source impedance of the variable power source to the variable impedance load.

2. A power conversion system as in claim 1, wherein the switching controller is configured to switch the power switches at a frequency of between about 20 KHz and 100 KHz to reduce the size of the input and output capacitors, and the input and output capacitors are selected such that the reflected source impedance represents a scaled version of the variable power source impedance characteristics.

3. A power conversion system as in claim 1, further comprising a motor drive as the variable impedance load and a maximum power point control logic adapted to vary the speed of a motor coupled to the motor drive based at least on the load voltage to cause the variable power source to operate at or near a maximum power point.

4. A power conversion system as in claim 3, further comprising a fluid pump coupled to the motor, wherein the power conversion system is configured to maximize a fluid pumping efficiency by causing the variable power source to operate at the target power point.

5. A power conversion system as in claim 3, further comprising a plurality of solar panels as the variable power source, and a plurality of power converter coupled to the plurality of solar panels and to the motor drive.

6. A power conversion system as in claim 3, wherein the power converter has an input impedance which is up to about 10% of the source impedance when the motor drive operates at the target power point.

7. A power conversion system as in claim 1, wherein the input and output impedances of the power converter are substantially negligible.

8. A power conversion system as in claim 1, further comprising a solar cell as the variable power source, wherein the power converter is integrated with the solar cell to form a single-piece structure.

9. A power conversion system as in any one of claim 1, wherein the switching controller is configured to switch the power switches at a frequency which is independent of the variable impedance load and the variable power source.

10. A power conversion system as in claim 9, wherein the switching controller is configured to switch the power switches in a symmetrical alternating mode at a maximum duty cycle.

11. A power conversion system as in claim 1, wherein the power converter is thermally insensitive in a temperature range between 10°

C. and 40°

C. and is insensitive to thermal cycling.

12. A power conversion system as in claim 1, wherein the power converter is devoid of electrolytic capacitors.

13. A method of operating a power conversion system, the method comprising:

receiving a variable power having an input voltage from a variable power source having a source impedance;

converting the variable power to a converted power by increasing the input voltage to an output voltage with a power converter;

receiving, by a variable impedance load, a load voltage based on the output voltage; and

reflecting the source impedance to the variable impedance load with the power converter.

14. A method of operating a power conversion system as in claim 13, wherein the power converter includes a switching controller, power switches controlled by the switching controller, a transformer coupled to the power switches, a rectification circuit configured to rectify an alternating current output from the transformer, and input and output capacitors, the switching controller configured to switch the power switches in an alternating unregulated manner to increase the input voltage to the output voltage.

15. A method of operating a power conversion system as in claim 14, wherein the switching controller is configured to switch the power switches at a frequency of between about 20 KHz and 100 KHz to reduce the size of the input and output capacitors, and the input and output capacitors are selected such that the reflected source impedance represents a scaled version of the variable power source impedance characteristics.

16. A method of operating a power conversion system as in claim 13, further comprising:

operating the power switches at a frequency which is independent of the variable impedance load and the variable power source.

17. A method of operating a power conversion system as in claim 13, further comprising:

operating the power switches in a symmetrical alternating mode at a maximum duty cycle.

18. A method of operating a power conversion system as in claim 13, further comprising:

varying, based on the load voltage, the speed of a motor coupled to the variable impedance load to operate the variable power source at a target power point corresponding to a maximum power point of the variable power source.

19. A method of operating a power conversion system as in claim 13, wherein the variable power source comprises a plurality of solar panels, further comprising:

each of a plurality of power converters receiving variable power from each of the plurality of solar panels; and

the variable impedance load receiving the converted power from each of the plurality of power converters.

20. A power conversion system comprising:

power converting means for increasing an input voltage of a variable power sourced by a variable power source into an output voltage;

an input terminal coupled to the power converting means and adapted to receive the variable power from the variable power source; and

an output terminal coupled to the power converting means and providing a converted power having the output voltage to the variable impedance load,

the power converting means configured to reflect a source impedance of the variable power source to the variable impedance load.