Distributed power harvesting systems using DC power sources

• US 9,088,178 B2
• Filed: 12/04/2007
• Issued: 07/21/2015
• Est. Priority Date: 12/06/2006
• Status: Active Grant

• Current Assignee: Solaredge Limited, Solaredge Technologies Incorporated
• Original Assignee: Solaredge Technologies Incorporated
• Inventors: Adest, Meir, Handelsman, Lior, Galin, Yoav, Fishelov, Amir, Sella, Guy
• Primary Examiner(s): Amrany, Adi
• Application Number:
  US11/950,271
• Publication Number:
  US 20080143188A1
• Time in Patent Office: 2,786 Days
• Field of Search: 307/43, 307/77, 307/82
• US Class Current: 1/1
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02M 7/42 Conversion of dc power input into ac power output without possibility of reversal
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

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 system comprising:

a plurality of direct current (DC) power sources;

a plurality of DC/DC power converters, each comprising;

output terminals,

input terminals coupled to a respective DC power source of the plurality of DC power sources,

a controller configured to set an input voltage and an input current at the input terminals to maximize power of the respective one of the DC power sources, and

a power conversion circuit configured to convert an input power received at the input terminals to an output power at the output terminals, the output terminals of all the DC/DC power converters coupled in series to form a series string; and

a power inverter comprising DC terminals and alternating current (AC) terminals, wherein the DC terminals of the power inverter are coupled to the series string, wherein the power inverter is configured to convert DC power received from the series string to AC power at the AC terminals, and wherein the power inverter includes circuitry with an inverter control loop configured to take a measurement of an inverter input voltage at the DC terminals and maintain the inverter input voltage at a regulated level based on the measurement.

2. The system of claim 1, wherein each of the DC/DC power converters further comprises a converter control loop configured to transfer a feedback signal from one of the input terminals to the controller.

3. The system of claim 2, wherein the power conversion circuit comprises:

a buck converter; and

a boost converter, wherein the controller is further configured to selectively activate the buck converter and the boost converter in response to the feedback signal.

4. The system of claim 3, wherein the power conversion circuit further comprises an inductor that is shared by the buck converter and the boost converter, and wherein the controller is further configured to perform pulse width modulation.

5. The system of claim 1, further comprising a shunt regulator coupled in parallel with the DC terminals.

6. The system of claim 1, further comprising one or more additional series strings, wherein each of the one or more additional series strings comprises one or more additional DC/DC power converters, wherein each of the one or more additional series strings is coupled in parallel to the series string, and wherein each of the one or more additional series strings is coupled to the power inverter.

7. The system of claim 1, wherein each of the DC/DC power converters further comprises:

a current sensor configured to provide current information, indicating the input current at the input terminals, to the controller; and

a voltage sensor configured to provide voltage information, indicating the input voltage at the input terminals, to the controller.

8. The system of claim 1, wherein each of the plurality of DC power sources comprises a solar panel or a building integrated solar panel.

9. The system of claim 1, wherein at least one of the plurality of DC power sources comprises a fuel cell.

10. The system of claim 1, wherein at least one of the plurality of DC power sources comprises a battery.

11. The system of claim 1, wherein each of the plurality of DC/DC power converters further comprises a safety module configured to limit the output power to a preset value until a predetermined event has occurred.

12. The system of claim 11, wherein the predetermined event comprises one of applying a load above a preset threshold to the DC/DC power converter and receiving a release signal.

13. The system of claim 1, further comprising a plurality of switching devices, each switching device of the plurality of switching devices configured to form a switchable current bypass to at least one of the DC power sources.

14. The system of claim 1, wherein at least one of the DC power sources comprises a solar panel that comprises a plurality of cell strings, each cell string comprising one or more serially connected solar cells, and wherein the system further comprises:

a switching device configured to selectively bypass one or more of the cell strings.

15. The system of claim 14, wherein the switching device comprises a transistor.

16. The system of claim 1, wherein each of the DC/DC power converters further comprises a monitoring module configured to monitor status related data, the status related data comprising at least one of the input current of the DC/DC power converter, the input voltage of the DC/DC power converter, temperature of the respective DC power source, input power to the DC/DC power converter, and illumination data.

17. An apparatus, comprising:

input terminals;

a sensor configured to sense at least one of a voltage across the input terminals and a current through the input terminals;

a direct current/direct current (DC/DC) power conversion circuit comprising at least one switching device and configured to convert an input power received at the input terminals to an output power at output terminals of the DC/DC power conversion circuit;

a controller configured to receive a feedback signal from the sensor and to set the voltage and the current at the input terminals to maximize the input power by adjusting a duty cycle of the at least one switching device;

one or more bypass terminals;

a plurality of bypass switching devices connected in series between the input terminals, one or more connections between the plurality of bypass switching devices connected respectively to the one or more bypass terminals;

a power inverter comprising DC terminals and alternating current (AC) terminals and configured to convert DC power received at the DC terminals to AC power at the AC terminals,

wherein one of the DC terminals of the power inverter is coupled to one of the output terminals of the DC/DC power conversion circuit, and

wherein the power inverter comprises a control device configured to maintain an inverter input voltage at the DC terminals of the power inverter at a regulated level.

18. The apparatus of claim 17, wherein each of the plurality of bypass switching devices is controlled to form a bypass in response to a respective control signal received from the controller when a reverse bias voltage is sensed across that bypass switching device.

19. The apparatus of claim 17, further comprising a DC power source connected to the input terminals.

20. The apparatus of claim 19, wherein the DC power source comprises a solar panel having a plurality of solar cell strings connected across the bypass switching devices via the bypass terminals and input terminals .

21. A method, comprising:

receiving power from a plurality of direct current (DC) power sources, each DC power source coupled to input terminals of a respective converter of a plurality of converters, each respective converter having output terminals, the plurality of converters connected in series at their respective output terminals to form a series string;

setting a voltage and current at input terminals of each respective converter such that the power of the DC power sources is maximized;

converting power received at the input terminals to output power on the output terminals of each respective converter; and

measuring with a control loop a voltage across the series string, and based on the measuring, maintaining the voltage across the series string at a regulated level.

22. The method of claim 21, the output powers on the output terminals of the plurality of converters summing to form DC series string power of the series string the method further comprising:

converting the DC series string power to alternating current (AC) power.

23. The method of claim 21, wherein the setting of the voltage and current at the input terminals to maximize the power of each of the DC power sources comprises:

performing a peak power tracking algorithm.

24. The method of claim 21, further comprising:

selectively bypassing a particular string of solar cells among a plurality of strings of solar cells included within one of the DC power sources.

25. The method of claim 24, further comprising:

determining that the particular string of solar cells enters reverse bias,

wherein the bypassing of the particular string of solar cells is performed in response to the determining that the particular string of solar cells enters reverse bias.

26. A system, comprising:

a plurality of direct current (DC) sources;

a plurality of DC/DC power converters, each of the DC/DC power converters comprising;

output terminals;

input terminals coupled to a respective DC power source of the plurality of the DC power sources,

a controller configured to set a voltage and a current at the input terminals of the DC/DC power converter, and

a power conversion circuit configured to convert an input power received at the input terminals to an output power at output terminals, the output terminals of all the DC/DC power converters coupled in series to form a series string; and

a closed loop circuit configured to regulate a voltage across the series string to a predetermined value.

27. The system of claim 26, further comprising a shunt regulator coupled in parallel to the series string and configured to dissipate excess power.

28. The system of claim 26, further comprising a power inverter coupled in parallel to the string and configured to convert DC power to alternating current (AC) power.

29. The system of claim 26, wherein the power conversion circuit comprises a buck plus boost converter.