AUTONOMOUS CHARGE BALANCING OF DISTRIBUTED AC COUPLED BATTERIES WITH DROOP OFFSET

• US 20170163049A1
• Filed: 12/05/2016
• Published: 06/08/2017
• Est. Priority Date: 12/03/2015
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Enphase Energy Incorporated
• Inventors: Zimmanck, Donald Richard
• Granted Patent: US 10,511,178 B2
• Time in Patent Office: Days
• CPC Class Codes: H02J 13/00007 using the power network as support for the transmission
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/0045 concerning the insertion or the connection of the batteries
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/123 the energy generation units being or involving renewable energy sources
• CPC Class Codes: Y04S 10/14 Energy storage units
• CPC Class Codes: Y04S 40/121 using the power network as support for the transmission

Abstract

A system and apparatus for autonomous charge balancing of an energy storage device of the microgrid. In one embodiment the apparatus comprises the energy storage device; and a power conditioner, coupled to the energy storage device, comprising a droop control module for operating the power conditioner, during an autonomous mode of operation, such that the state of charge of the energy storage device is autonomously driven toward the state of charge of at least one other energy storage device of the microgrid.

Claims

1. An apparatus for autonomous charge balancing of an energy storage device of a microgrid, comprising:

the energy storage device; and

a power conditioner, coupled to the energy storage device, comprising a droop control module for operating the power conditioner, during an autonomous mode of operation, such that the state of charge of the energy storage device is autonomously driven toward the state of charge of at least one other energy storage device of the microgrid.

2. The apparatus of claim 1, wherein operating the power conditioner such that the state of charge of the energy storage device is autonomously driven toward the state of charge of at least one other energy storage device of the microgrid comprises operating the power conditioner to have a droop offset based on the state of charge of the energy storage device.

3. The apparatus of claim 2, wherein the droop offset is further based on a predetermined state of charge target.

4. The apparatus of claim 2, wherein the droop offset is inversely proportional to state of charge of the energy storage device.

5. The apparatus of claim 2, wherein the power conditioner is a DC-AC inverter.

6. The apparatus of claim 5, wherein the DC-AC inverter is a voltage forming inverter.

7. The apparatus of claim 5, wherein the DC-AC inverter is a current feeding inverter.

8. The apparatus of claim 1, wherein the energy storage device is a battery.

9. A system for autonomous charge balancing of a plurality of energy storage devices of a microgrid, comprising:

the plurality of energy storage devices; and

a plurality of power conditioners coupled via a power bus and coupled to the plurality of energy storage devices in a one-to-one correspondence, wherein each power conditioner comprises a droop control module for operating the power conditioner during an autonomous mode of operation, and wherein during the autonomous mode of operation the plurality of power conditioners are operated such that the states of charge of the plurality of energy storage devices are autonomously driven toward being equal.

10. The system of claim 9, wherein operating the power conditioner during an autonomous mode of operation comprises operating the power conditioner to have a droop offset based on the state of charge of the corresponding energy storage device.

11. The system of claim 10, wherein the droop offset is further based on a predetermined state of charge target.

12. The system of claim 11, wherein the predetermined state of charge target is the same for each energy storage device of the plurality of energy storage devices.

13. The system of claim 10, wherein the droop offset is inversely proportional to state of charge of the corresponding energy storage device.

14. The system of claim 10, wherein each power conditioner of the plurality of power conditioners is a DC-AC inverter.

15. The system of claim 14, wherein the DC-AC inverter is a voltage forming inverter.

16. The system of claim 14, wherein the DC-AC inverter is a current feeding inverter.

17. The system of claim 9, wherein each energy storage device of the plurality of energy storage devices is a battery.

18. The system of claim 9, wherein the microgrid further comprises at least one additional power conditioner coupled to the power bus and coupled to a corresponding energy source.

19. The system of claim 18, wherein the corresponding energy source is a renewable energy source.

20. The system of claim 18, wherein the corresponding energy source is a photovoltaic (PV) module.