Series stacked DC-DC converter with serially connected DC power sources and capacitors

• US 10,651,735 B2
• Filed: 07/14/2017
• Issued: 05/12/2020
• Est. Priority Date: 02/06/2017
• 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
• Primary Examiner(s): Ahmed, Yusef A
• Assistant Examiner(s): Ahmad, Shahzeb K
• Application Number:
  US15/650,355
• Publication Number:
  US 20180226890A1
• Time in Patent Office: 1,033 Days
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• 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: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/0074 Plural converter units whose inputs are connected in series
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 1/0093 wherein the output is created by adding a regulated voltage to or subtracting it from an unregulated input
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: H02S 50/00 Monitoring or testing of PV systems, e.g. load balancing or fault identification
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• 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 sources. The DC sources may be photovoltaic panels. One aspect includes a stack of DC power sources (e.g., photovoltaic modules) with a DC to DC converter (e.g., power optimizer) associated with each DC power source. An output capacitor of a DC to DC converter is connected in series with its DC power source. Thus, there is a string of DC power sources and output capacitors connected in electrical series. The DC output of the system is a series connection of the DC power sources and the output capacitors. This reduces stress on the output capacitors, while allowing for efficient power generation by the DC power sources.

Claims

1. A system comprising:

a plurality of power units, each power unit comprising;

a DC to DC converter having a first terminal, a second terminal, and a third terminal, the DC to DC converter having an output capacitor coupled between the first terminal and the second terminal; and

a direct current (DC) power source having a DC output coupled between the second terminal and the third terminal;

the plurality of power units are series coupled between a first power unit at a first end of the series and a second power unit at a second end of the series, comprising a coupling between the third terminal of the DC to DC converter in one of the power units and the first terminal of the DC to DC converter in a next power unit in the series in a direction from the first power unit to the second power unit; and

a DC voltage output configured to receive a voltage between the first terminal of the DC to DC converter in the first power unit and the third terminal of the DC to DC converter in the second power unit, the voltage is a summation of individual voltages across each of the DC power sources and the output capacitor of each of the DC to DC converters.

2. The system of claim 1, further comprising:

one or more power regulating circuits configured to control the DC to DC converters to regulate power output from the DC power sources.

3. The system of claim 2, wherein the one or more power regulating circuits are configured to control a duty cycle of each of the DC to DC converters to control a voltage on the output capacitor of each DC to DC converter.

4. The system of claim 2, wherein the DC power sources comprise photovoltaic modules.

5. The system of claim 4, wherein the one or more power regulating circuits are configured to control the DC to DC converters to operate the photovoltaic modules at maximum power points.

6. The system of claim 4, further comprising:

a solar inverter having a pair of input terminals, wherein the pair of input terminals of the solar inverter are electrically coupled across a series combination of the DC power sources and the output capacitor of each DC to DC converter.

7. The system of claim 6, wherein the solar inverter is configured to regulate a voltage at the pair of input terminals to a target voltage.

8. The system of claim 1, wherein the DC to DC converters comprise:

a buck converter configured as a DC power optimizer.

9. The system of claim 1, wherein the DC to DC converters comprise:

a boost converter configured as a DC power optimizer.

10. The system of claim 1, wherein the DC to DC converters comprise:

a buck-boost converter configured as a DC power optimizer.

11. The system of claim 1, wherein the DC power sources comprise batteries.

12. The system of claim 1, wherein the DC power sources comprise photovoltaic modules, and further comprising:

a battery having a pair of input terminals, wherein the pair of input terminals of the battery are electrically coupled across a series combination of the photovoltaic modules and the output capacitor of each DC to DC converter.

13. A method of regulating power in a system comprising power units coupled in series, each power unit comprising a power optimizer having an output capacitor coupled between a first terminal and a second terminal of the power optimizer, each power unit comprising a photovoltaic module coupled between the second terminal and a third terminal of the power optimizer, the power units are series coupled between a first power unit at a first end of the series and a second power unit at a second end of the series, comprising a coupling between the third terminal of the power optimizer in one of the power units in the series to the first terminal of the power optimizer in a next power unit in the series in a direction from the first power unit to the second power unit, the method comprising:

monitoring an output signal at each of the photovoltaic modules;

operating the power optimizers responsive to the output signals to regulate power output of the photovoltaic modules; and

providing a DC voltage that is a summation of an individual voltage across each of the photovoltaic modules and an individual voltage across each of the output capacitors to a solar inverter or a battery, the DC voltage taken between the first terminal of the power optimizer in the first power unit and the third terminal of the power optimizer in the second power unit.

14. The method of claim 13, wherein operating the power optimizers responsive to the output signals to regulate power output of the photovoltaic modules comprises:

controlling the power optimizers to regulate voltages across each of the output capacitors.

15. The method of claim 14, wherein the controlling the power optimizers to regulate voltages across each of the output capacitors comprises:

establishing duty cycles of the power optimizers.

16. The method of claim 14, wherein the controlling the power optimizers to regulate voltages across each of the output capacitors comprises:

establishing either a buck mode or a boost mode for each of the power optimizers.

17. A photovoltaic power transfer system, comprising:

series stacked systems coupled in series and/or parallel, each of the series stacked systems comprising;

a plurality of power units, each of the power units comprising;

a photovoltaic module having a DC voltage output;

a capacitor; and

a power optimizer having a first terminal, a second terminal, and a third terminal, the capacitor coupled between the first terminal and the second terminal, the DC voltage output of the photovoltaic module coupled between the second terminal and the third terminal;

the power units are series coupled between a first power unit at a first end of the series and a second power unit at a second end of the series, comprising a coupling between the third terminal of the power optimizer in one of the power units in the series to the first terminal of the power optimizer in a next power unit in the series in a direction from the first power unit to the second power unit; and

a DC voltage output of the photovoltaic power transfer system that is configured to receive a voltage between the first terminal of the power optimizer in the first power unit and the third terminal of the power optimizer in the second power unit, the voltage being a summation of a DC voltage from the DC voltage output of the photovoltaic module and a voltage across the capacitor from each of the plurality of power units in a string of the series stacked systems that are coupled in electrical series.

18. The system of claim 17, further comprising:

a solar inverter having a DC voltage input and an AC voltage output, wherein the DC voltage input is coupled across a series combination of the photovoltaic modules and the capacitors of the plurality of power units in a string of the series stacked systems that are coupled in electrical series.

19. The system of claim 18, wherein the power optimizer is configured to control the voltage across the capacitor responsive to an output condition of the photovoltaic module.

20. The system of claim 19, wherein the power optimizer is configured to regulate a power output of the photovoltaic module.