Multiple buck stage single boost stage optimizer

• US 10,333,314 B2
• Filed: 04/17/2017
• Issued: 06/25/2019
• Est. Priority Date: 04/17/2017
• Status: Active Grant

• Current Assignee: Huawei Digital Power Technologies Company Limited (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Dai, Heping, Mao, Xiaolin
• Primary Examiner(s): Dole, Timothy J.
• Assistant Examiner(s): Ahmad, Shahzeb K
• Application Number:
  US15/489,278
• Publication Number:
  US 20180301905A1
• Time in Patent Office: 799 Days
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• 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 7/483 Converters with outputs that each can have more than two voltages levels
• CPC Class Codes: H02M 7/4835 comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
• CPC Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

The disclosure relates to technology for providing power, voltage, and/or current from a combination of DC power sources, such as photovoltaic modules or DC batteries. One aspect includes a buck-boost optimizer having a number of inductorless buck stages and a boost stage. The buck-boost optimizer may be used within a power generation system. The combined output voltages of each of the buck stages may be input to the boost stage. The boost stage may have an inductor that may serve as an energy storage device to boost a voltage, as well as to filter a signal from the buck stages. Thus, the buck-boost optimizer may use a single inductor. Having a single inductor provides for a very efficient power generation system. Also, cost and size of components in the power generation system may be reduced.

Claims

1. A system comprising:

a plurality of buck stages each having an input configured to receive a DC voltage from a DC power source and a buck stage output configured to provide a DC voltage;

logic configured to operate the plurality of buck stages to regulate a power output of each of the DC power sources, including operate the respective buck stages at target duty cycles to maintain a target power efficiency for each buck stage, the combined DC voltages from the plurality of buck stage outputs depends on the target duty cycles; and

a boost stage comprising a boost stage output and a single boost stage input configured to receive the combined DC voltages from the plurality of buck stage outputs;

wherein the logic is further configured to instruct the boost stage to reduce the DC voltage at the input of the boost stage below a threshold voltage responsive to a determination that the combined DC voltages of the plurality of buck stages will be below the threshold voltage in order to maintain the target duty cycles of the respective buck stages.

2. The system of claim 1, wherein the boost stage further comprises a filter that is configured to receive a current output of the plurality of buck stages.

3. The system of claim 2, wherein the boost stage is configured to use the filter as an energy storage device.

4. The system of claim 3, wherein the filter is an inductor.

5. The system of claim 4, wherein the plurality of buck stages and the boost stage share the inductor.

6. The system of claim 1, wherein the DC voltage sources are photovoltaic modules, wherein the target power efficiency for each buck stage is at the maximum power point of the respective photovoltaic module.

7. The system of claim 1, further comprising:

a DC to AC converter having an input connected to the boost stage output, wherein the DC to AC converter is configured to regulate a DC voltage at the input of the DC to AC converter.

8. The system of claim 7, wherein the logic is further configured to:

control a duty cycle of the boost stage to reduce the voltage at the input of the boost stage relative to the voltage at the output of the boost stage responsive to a determination that the DC voltage at the input of the DC to AC converter does not meet a criterion.

9. The system of claim 1, wherein the plurality of buck stages are configured to generate a pulse width modulated output voltage at the same switching frequency, wherein the plurality of buck stages are configured to interleave the pulse width modulated output voltages.

10. The system of claim 1, wherein the plurality of buck stages are inductorless.

11. A method of operating a power generation system, the method comprising:

receiving DC voltages from each of respective ones of a plurality of photovoltaic modules at a corresponding plurality of buck stages;

operating each of the plurality of buck stages to regulate a power output of the corresponding photovoltaic modules, including generating a DC output voltage for each buck stage, including operating the respective buck stages at target duty cycles to maintain a target power efficiency for each buck stage, the combined DC voltages from the plurality of buck stage outputs depends on the target duty cycles;

receiving a combined DC output voltage from all of the plurality of buck stages at an input of a single boost stage;

operating the single boost stage to boost the combined output voltage from the plurality of buck stages, including instructing the boost stage to reduce the DC voltage at the input of the boost stage below a threshold voltage responsive to a determination that the combined DC voltages of the plurality of buck stages will be below the threshold voltage in order to maintain the target duty cycles of the respective buck stages to thereby allow the respective buck stages to be operated at the target duty cycles; and

providing the boosted voltage to a solar inverter.

12. The method of claim 11, further comprising receiving an output current of the plurality of buck stages at a filter of the boost stage.

13. The method of claim 12, wherein the filter comprises an inductor, wherein operating the boost stage to boost the output voltage from the buck stages comprises storing energy in the inductor.

14. The method of claim 11, further comprising:

boosting the reduced DC voltage at the input of the boost stage to maintain the output voltage of the boost stage at a target voltage level for the solar inverter.

15. The method of claim 11, wherein operating each of the plurality of buck stages to regulate a power output of the corresponding photovoltaic modules comprises:

generating a pulse width modulated output voltage at each of the buck stages at the same switching frequency; and

interleaving the pulse width modulated output voltages.

16. A photovoltaic power system, comprising:

a plurality of photovoltaic modules, each configured to provide a DC voltage;

a buck-boost convertor comprising a plurality of buck stages and a single boost stage, wherein each of the buck stages comprises an input configured to receive the DC voltage from one of the photovoltaic modules, wherein each of the buck stages comprises an output configured to provide a DC voltage, wherein each of the buck stages is configured to regulate a power output of the corresponding photovoltaic module, wherein the single boost stage comprises a single input configured to receive the combined DC voltages from the plurality of buck stage outputs, wherein the single boost stage comprises an output configured to provide a DC voltage; and

logic configured to operate the respective buck stages at target duty cycles to maintain a target power efficiency for each buck stage, the combined DC voltages from the plurality of buck stage outputs depends on the target duty cycles, the logic is further configured to instruct the boost stage to reduce the DC voltage at the input of the boost stage below a threshold voltage responsive to a determination that the combined DC voltages of the plurality of buck stages will be below the threshold voltage in order to maintain the target duty cycles of the respective buck stages.

17. The photovoltaic power system of claim 16, wherein the plurality of buck stages are configured to provide a series output current, wherein the boost stage comprises an inductor that is configured to receive the series current.

18. The photovoltaic power system of claim 17, wherein the boost stage is configured to use the inductor as an energy storage device to boost the combined DC voltages from the plurality of buck stages and to provide the boosted voltage at the output of the boost stage.

19. The photovoltaic power system of claim 16, wherein the photovoltaic power system further comprises a plurality of buck-boost convertors as recited in claim 16, wherein the plurality of buck-boost convertors are connected in series, wherein the combined DC voltage output from the boost stages of the plurality of buck-boost convertors is provided to a solar inverter.

20. The photovoltaic power system of claim 16, wherein the photovoltaic power system further comprises:

a plurality of buck-boost convertors as recited in claim 16, wherein the plurality of buck-boost convertors are connected in series;

an additional boost stage having an input configured to receive the combined DC voltages from the boost stages of the plurality of buck-boost convertors; and

a solar inverter having a DC input configured to receive a DC voltage from an output of the additional boost stage.

21. The photovoltaic power system of claim 16, wherein the plurality of buck stages are configured to generate a pulse width modulated output voltage at the same switching frequency, wherein the plurality of buck stages are configured to interleave the pulse width modulated output voltages.

22. The photovoltaic power system of claim 16, wherein a first of the photovoltaic modules comprises a single photovoltaic panel, multiple photovoltaic panels that are connected in series, or a sub-string of a photovoltaic panel.

23. The photovoltaic power system of claim 16, wherein the photovoltaic power system comprises a plurality of buck-boost convertors as recited in claim 16, wherein the plurality of buck-boost convertors are connected in series, connected in parallel, or a combination of series and parallel.