POWER BALANCING IN A MULTI-PHASE SYSTEM

• US 20140191583A1
• Filed: 03/13/2013
• Published: 07/10/2014
• Est. Priority Date: 01/04/2013
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Enecsys Limited
• Inventors: Chisenga, Lesley, Garrity, Paul, Jungreis, Aaron
• Granted Patent: US 9,257,837 B2
• Time in Patent Office: Days
• US Class Current: 307/82
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 3/26 Arrangements for eliminating or reducing asymmetry in polyphase networks
• CPC Class Codes: H02M 7/44 by static converters
• CPC Class Codes: Y02B 10/10 Photovoltaic [PV]
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 40/50 Arrangements for eliminating or reducing asymmetry in polyphase networks
• CPC Class Codes: Y02P 80/20 using renewable energy

Abstract

Some embodiments of the invention provide a method for balancing the power output to each phase of a set of micro-inverters. The method of some embodiments is performed by a gateway, which receives output messages from a plurality of micro-inverters. The gateway identifies the phase of each micro-inverter and calculates the output of the plurality of micro-inverters to each power line of a multi-phase system. The gateway then sends control signals to the micro-inverters to control the output of each micro-inverter to maintain a balanced aggregate power output to each phase of the power grid.

Claims

1. A method for maintaining balanced energy transmissions between different phases of a multi-phase power system, the method comprising:

for each phase of the multi-phase system, identifying a set of micro-inverters associated with the phase;

calculating an aggregate power output for each phase of the multi-phase system; and

controlling an individual power output of at least one micro-inverter of at least one set of micro-inverters in order to reduce the imbalance between the power outputs to each phase of the multi-phase power system.

2. The method of claim 1, wherein identifying a set of micro-inverters comprises:

receiving a message from each micro-inverter;

recording a received time of each message; and

using received time of each message to determine the phase for each micro-inverter.

3. The method of claim 1, wherein controlling the individual power output of the at least one micro-inverter comprises sending a control signal to the micro-inverter over a communication system.

4. The method of claim 3, wherein the communication system is a wireless communication system.

5. The method of claim 1, wherein controlling the individual power output comprises setting a same threshold power output level for the at least one micro-inverter as for all of the micro-inverters in the same set of micro-inverters.

6. The method of claim 1, wherein controlling the individual power output of the at least one micro-inverter comprises setting a threshold output level for the micro-inverter that is different from the threshold output level of a micro-inverter in a different set of micro-inverters of another phase.

7. The method of claim 1, wherein controlling the individual power output comprises preventing the at least one micro-inverter from injecting power into the multi-phase power system.

8. A multi-phase power system comprising:

a plurality of sets of micro-inverters, each set of micro-inverters for injecting power into a power line of a particular phase of a multi-phase AC grid mains;

a gateway for (i) receiving a set of information comprising the individual power output from each micro-inverter of the plurality of sets of micro-inverters, (ii) calculating an aggregate power output of each set of micro-inverters, and (iii) balancing the output to different phases of the multi-phase AC grid mains, the balancing comprising controlling the output of at least one micro-inverter of at least one set of micro-inverters.

9. The system of claim 8, further comprising at least one sensor for measuring the aggregate power output to the power line of the particular phase of the multi-phase AC grid mains.

10. The system of claim 8, wherein controlling the output of at least one micro-inverter comprises sending control signals to the at least one micro-inverter based on the set of information.

11. The system of claim 10, wherein the control signals comprise instructions to change the output of the at least one micro-inverter.

12. The system of claim 8, wherein balancing the output to the phases of the multi-phase power further comprises ensuring that the output to each phase of the multi-phase power grid is within a threshold value of the outputs to the other phases.

13. The system of claim 8, wherein the set of information comprises a value of at least one of voltage output, current output, and power output.

14. The system of claim 13, wherein the value is an average output over a period of time.

15. The system of claim 10, wherein the control signals comprise instructions to prevent a micro-inverter from injecting power into the multi-phase power system.

16. The system of claim 10, wherein each micro-inverter comprises (i) a wireless transmitter for transmitting the sets of information and (ii) a wireless receiver for receiving the control signals.

17. A non-transitory machine readable medium comprising a program to be executed on at least one processing unit, the program comprising sets of instructions for:

identifying, for each power line of a multi-phase AC grid mains, a set of micro-inverters that provides power to the power line;

calculating an aggregate power output for each set of micro-inverters; and

balancing the aggregate power output of each set of micro-inverters, the balancing comprising controlling the output of at least one micro-inverter of at least one set of micro-inverters.

18. The non-transitory machine readable medium of claim 17, wherein the program further comprises sets of instructions for receiving data from each set of micro-inverters.

19. The non-transitory machine readable medium of claim 17, wherein calculating an aggregate power output comprises receiving data from sensors from each phase of the AC grid mains.

20. The non-transitory machine readable medium of claim 17, wherein controlling the output of at least one micro-inverter comprises updating the output threshold for all of the micro-inverters providing power to a particular phase of the multi-phase system.

21. A method for controlling power being injected into different power lines of a multi-phase power system, the method comprising:

receiving messages from a plurality of micro-inverters, wherein each message is generated by a micro-inverter when a power line connecting the micro-inverter is at a particular phase of an AC cycle;

identifying a first power line as a power line that is connected to a first micro-inverter transmitting the first message;

calculating a timing differential between the first message received from the first micro-inverter and a second message received from the second micro-inverter; and

identifying a second power line as a power line connected to a second micro-inverter based on the calculated timing differential.

23. The method of claim 21, wherein each micro-inverter generates a message when a power line connecting the micro-inverter is at a voltage peak of an AC cycle.

24. The method of claim 21, wherein each micro-inverter generates two messages in each AC cycle.