METHOD FOR DISTRIBUTED POWER HARVESTING USING DC POWER SOURCES

• US 20080150366A1
• Filed: 12/04/2007
• Published: 06/26/2008
• Est. Priority Date: 12/06/2006
• Status: Active Grant

• Current Assignee: Solaredge Limited, Solaredge Technologies Incorporated
• Original Assignee: Solaredge Limited
• Inventors: Galin, Yoav, Fishelov, Amir, Adest, Meir, Sella, Guy, Handelsman, Lior
• Granted Patent: US 8,013,472 B2
• Time in Patent Office: Days
• US Class Current: 307/77
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/18 Arrangements for adjusting, eliminating or compensating reactive power in networks for adjustment of voltage H02J3/16
• 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: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H02M 7/44 by static converters
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving

Abstract

A system and method for combining power from DC power sources. Each power source is coupled to a converter. Each converter converts input power to output power by monitoring and maintaining the input power at a maximum power point. Substantially all input power is converted to the output power, and the controlling is performed by allowing output voltage of the converter to vary. The converters are coupled in series. An inverter is connected in parallel with the series connection of the converters and inverts a DC input to the inverter from the converters into an AC output. The inverter maintains the voltage at the inverter input at a desirable voltage by varying the amount of the series current drawn from the converters. The series current and the output power of the converters, determine the output voltage at each converter.

Claims

1. A method for harvesting power from a distributed power system having a plurality of DC power sources and a plurality of DC power converters, the method comprising:

coupling each of the power sources to a respective DC power converter;

coupling the power converters in series, to thereby form at least one serial string;

coupling the serial string to a power delivery device;

fixing one of input voltage or input current to the power delivery device to a predetermined value, thereby forcing current flowing through the serial string to vary according to power provided by the power sources;

controlling power output from each power source individually and individually varying the input voltage and current to each respective converter according to a predetermined criteria.

2. The method of claim 1, wherein fixing one of the input voltage or input current comprises fixing to a predetermined constant value.

3. The method of claim 1, wherein coupling the serial string to a power delivery device comprises coupling the serial string to a DC/AC inverter and fixing the input voltage to the inverter.

4. The method of claim 1, wherein monitoring power output comprises tracking maximum power point of the power source, and individually varying the input voltage and current comprises setting the input voltage and current so as to draw maximum power from each power source.

5. The method of claim 1, further comprising individually converting the input voltage and current of each converter to output power at current level dictated by the current flowing through the serial string and at a floating voltage.

6. The method of claim 3, further comprising individually converting the input voltage and current of each converter to output power at current level dictated by the current flowing through the serial string and at a floating voltage.

7. The method of claim 1, further comprising monitoring load on each converter individually and limiting power output from each converter to a preset safe level until the load reaches a preset value.

8. The method of claim 1, further comprising monitoring power output of at least one of the power source and DC power converter and directing current to a bypass when the power output exhibits predetermined characteristics.

9. The method of claim 1, further comprising individually operating each power converter to monitor and report power related data, the power related data comprising at least one of:

input current to the converter, input voltage to the converter, temperature of the power source, input power to the converter, and available illumination.

10. In a distributed power system having a plurality of DC power sources coupled to a central load, a method for improving the reliability of components within the load, comprising:

coupling the DC power sources to the central load;

maintaining the input to the central load to a fixed predetermined voltage, the voltage being a safe operating voltage for the components within the load;

varying the current input to the central load according to the power drawn from the DC power sources.

11. The method of claim 10, wherein the central load comprises a DC/AC inverter, and the step of maintaining the input comprises maintaining the input voltage to the inverter.

12. The method of claim 11, wherein coupling the DC power sources comprises coupling each of a plurality of solar panels to a respective converter from a plurality of converters, and coupling all of the converters to the inverter.

13. The method of claim 12, further comprising operating each converter to boost the voltage obtained from a respective solar panel as soon as the respective solar panel starts to output electrical energy.