Photovoltaic DC/DC micro-converter

• US 9,502,895 B1
• Filed: 05/19/2015
• Issued: 11/22/2016
• Est. Priority Date: 07/01/2008
• Status: Expired due to Fees

• Current Assignee: Perfect Galaxy International Limited
• Original Assignee: Perfect Galaxy International Limited
• Inventors: Casey, Leo Francis, Mossoba, Joseph T.
• Primary Examiner(s): Deberadinis, Robert
• Application Number:
  US14/716,818
• Time in Patent Office: 553 Days
• Field of Search: 307/43, 307/82
• US Class Current: 1/1
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H02J 1/12 Parallel operation of dc generators with converters, e.g. with mercury-arc rectifier
• 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 3/04 by static converters
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A photo-voltaic (PV) power generating system and a control system for PV array string-level control and PV modules serially-connected into strings of PV modules. The system includes plural parallel strings of serially-connected powergenerating photovoltaic modules that form a PV array, DC/DC micro-converters that are coupled to a DC voltage buss and to the output of a corresponding photovoltaic module or to the output of a string of photovoltaic modules; a gating or central inverter; and a control system. The micro-converters are structured and arranged to include at least one of: an active clamp device, a ground fault detection device, and a fractional power converter that injects power in series or in parallel with voltage or current from the power-generating portion onto the DC buss.

Claims

1. A system for photovoltaic power generation comprising:

a plurality of power-generating photovoltaic strings, wherein each of the power-generating photovoltaic strings comprise a plurality of power-generating photovoltaic modules;

a plurality of direct current (DC)/DC micro-converters, wherein the DC/DC micro-converters are electrically coupled to the power-generating photovoltaic modules, to the power-generating photovoltaic string, or both;

a plurality of active clamps electrically coupled to the DC/DC micro-converters, wherein the plurality of active claims are configured to limit the power-generating photovoltaic strings to less than or equal to pre-established threshold voltage by creating a short-circuit;

a gating inverter electrically coupled to DC/DC micro-converters and to one or more electrical loads; and

a central controller electrically coupled to the gating inverter.

2. The system of claim 1, wherein the active clamps are integrated within at least some of the DC/DC micro-converters.

3. The system of claim 1, wherein at least some of the plurality of active clamps comprises a voltage sensing component configured to measure an output voltage for each of the power-generating photovoltaic strings.

4. The system of claim 3, wherein the at least some of the plurality of active clamps comprises a comparator configured to compare the output voltage for at least one of the power-generating photovoltaic strings with a pre-established threshold voltage.

5. The system of claim 4, wherein the at least some of the plurality of active clamps comprise a controller configured to switch one or more switching components to an on state to create the short-circuit based upon the output of the comparator.

6. The system of claim 4, wherein the pre-established threshold voltage is less than or equal to a limiting breakdown voltage of the power-generating photovoltaic modules.

7. The system of claim 1, wherein the gating inverter is electrically coupled to the DC/DC micro-converters via one or more high voltage DC buss such that the power generated from power-generating photovoltaic modules are not stored at the power-generating photovoltaic modules.

8. The system of claim 1, wherein the DC/DC micro-converters comprise at least one maximum power point controller configured to regulate output voltages of the power-generating photovoltaic strings based upon the maximum power of the power-generating photovoltaic strings.

9. A system for photovoltaic power generation comprising:

a plurality of power-generating photovoltaic strings comprising a plurality of power-generating photovoltaic modules;

a plurality of direct current (DC)/DC micro-converters, wherein the DC/DC micro-converters are electrically coupled to at least one of the following;

the power-generating photovoltaic modules or the power-generating photovoltaic string;

at least one ground fault detector electrically coupled to the DC/DC micro-converters, wherein the at least one ground fault detector is configured to detect a ground fault for one of the power-generating photovoltaic strings;

an inverter electrically coupled to DC/DC micro-converters and to one or more loads; and

a controller electrically coupled to the inverter.

10. The system of claim 9, wherein the at least one ground fault detector is integrated within at least one of the DC/DC micro-converters.

11. The system of claim 9, wherein the at least one ground fault detector is configured to disconnect the one of the power-generating photovoltaic strings from a voltage buss when detecting the ground fault for the one of the power-generating photovoltaic strings, wherein the voltage buss electrically couples the inverter to the DC/DC micro-converters.

12. The system of claim 9, wherein the inverter comprises an energy storage and is electrically coupled to the DC/DC micro-converters via at least one high voltage DC buss, and wherein the power generated from power-generating photovoltaic modules are stored at the energy storage of the inverter.

13. The system of claim 9, wherein each of the DC/DC micro-converters comprise a maximum power point controller adapted to regulate output voltages from a corresponding power-generating photovoltaic strings of the power-generating photovoltaic strings based on a point of maximum power for the corresponding power-generating photovoltaic string.

14. The system of claim 9, wherein the at least one ground fault detector is configured to detect the ground fault for the one of the power-generating photovoltaic strings by:

measuring the voltages of the one of the power-generating photovoltaic strings and the output voltage of the inverter;

measuring the input current of the DC/DC micro-converter and the output current of the DC/DC micro-converter associated with the one of the power-generating photovoltaic strings; and

comparing the product of the voltage of the one of the power-generating photovoltaic strings and the input current of the DC/DC micro-converter associated with the one of the power-generating photovoltaic strings with the product of the output voltage of the inverter and the output current of the DC/DC micro-converter associated with the one of the power-generating photovoltaic strings.

15. A system for photovoltaic power generation comprising:

a plurality of power-generating photovoltaic strings comprising a plurality of power-generating photovoltaic modules;

a plurality of direct current (DC)/DC micro-converters, wherein the DC/DC micro-converters are electrically coupled to the power-generating photovoltaic modules, to the power-generating photovoltaic string, or both, and wherein at least some of the DC/DC micro-converters comprise a fractional power converter adapted to draw a fraction of a total power from the plurality of power-generating photovoltaic strings;

an inverter electrically coupled to DC/DC micro-converters and to at least one grid; and

a control system electrically coupled to the inverter.

16. The system of claim 15, wherein the fractional power converter is a voltage-injection fractional power converter.

17. The system of claim 16, wherein the voltage-injection fractional power converter is adapted to inject a voltage that is in series with an input voltage supplied by the power-generating photovoltaic strings.

18. The system of claim 15, wherein the fractional power converter is a current-injection fractional power converter.

19. The system of claim 18, wherein the current-injection fractional power converter is adapted to inject a current that is in parallel with an output current directly generated by the power-generating photovoltaic strings.

20. The system of claim 15, wherein the fractional power converter is bi-directional, wherein the inverter comprises an energy storage, wherein the inverter is electrically coupled to the DC/DC micro-converters via at least one high voltage DC buss, and wherein the power generated from power-generating photovoltaic modules are stored at the energy storage of the inverter without storing the power generated from power-generating photovoltaic modules at the power-generating photovoltaic modules.