Power transfer management for local power sources of a grid-tied load

• US 8,693,228 B2
• Filed: 02/18/2010
• Issued: 04/08/2014
• Est. Priority Date: 02/19/2009
• Status: Active Grant

• Current Assignee: Apparent Labs LLC
• Original Assignee: William B. Westbrock, Jr.
• Inventors: Matan, Stefan, Westbrock, William B. Jr., Horton, Fred C., Klemm, Joseph M., Marrone, Frank P., McKinley, Arnold F., Wiseman, Kurt W.
• Primary Examiner(s): Laxton, Gary L
• Application Number:
  US12/708,514
• Publication Number:
  US 20100208501A1
• Time in Patent Office: 1,510 Days
• Field of Search: 363/95, 363/97, 363/98, 363/131, 363/132, 307/18, 307/22, 307/26, 307/31, 307/82, 307/151, 323/205, 323/307, 323/207, 323/906
• US Class Current: 363/97
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G05F 1/70 Regulating power factor; Regulating reactive current or power
• CPC Class Codes: H02J 3/18 Arrangements for adjusting, eliminating or compensating reactive power in networks for adjustment of voltage H02J3/16
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 3/50 Controlling the sharing of the out-of-phase component
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• 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
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

A power transfer system provides power factor conditioning of the generated power. Power is received from a local power source, converted to usable AC power, and the power factor is conditioned to a desired value. The desired value may be a power factor at or near unity, or the desired power factor may be in response to conditions of the power grid, a tariff established, and/or determinations made remotely to the local power source. Many sources and power transfer systems can be put together and controlled as a power source farm to deliver power to the grid having a specific power factor characteristic. The farm may be a grouping of multiple local customer premises. AC power can also be conditioned prior to use by an AC to DC power supply for more efficient DC power conversion.

Claims

1. A method comprising:

receiving, at a power converter, direct current (DC) power from a local power source, the local power source and the power converter electrically located on a same side of a point of connection to a utility power grid as a local load tied to the power grid, where the local load includes a consumer premises of the power grid;

receiving characteristic shape and phase information about a target periodic waveform having a phase with respect to an AC voltage of the power grid;

converting with the power converter the DC power to alternating current (AC) power to deliver to the local load, including generating an output waveform to generate a current with output hardware;

conditioning a power factor of the AC power by controlling the phase of the generated current with respect to phase of the voltage of the power grid, including

sampling the output waveform;

comparing the output waveform to a corresponding reference output waveform, the reference output waveform representing an ideal version of the target periodic waveform based on the received characteristic shape and phase information;

generating a feedback signal based on comparing the output waveform to the reference output waveform; and

adjusting an operation of the output hardware at runtime based on the feedback signal, wherein adjusting the operation of the output hardware converges the output waveform toward the reference output waveform and phase; and

delivering the conditioned AC power on the local load side of the power grid.

2. The method of claim 1, wherein receiving at the power converter comprises:

receiving at a micro-inverter installed on the consumer premises.

3. The method of claim 1, wherein receiving power from the local power source comprises:

receiving power from a metastable power source.

4. The method of claim 3, wherein receiving power from the metastable local power source comprises:

receiving power from a solar power source, a tidal power source, a wind power source, or a thermally coupled heat source.

5. The method of claim 1, wherein conditioning the power factor further comprises:

conditioning the power factor by adjusting a phase of generated AC current with a table-based phase adjustment.

6. The method of claim 1, wherein conditioning the power factor further comprises:

conditioning the power factor of the generated AC current based on conditions of the power grid.

7. The method of claim 6, wherein conditioning the power factor based on conditions of the power grid further comprises:

measuring one or more conditions of the power grid from the customer premises.

8. The method of claim 6, wherein conditioning the power factor based on conditions of the power grid further comprises:

receiving a remote communication from a device not located on the same side of the point of connection indicating a power factor adjustment; and

adjusting the power factor in response to receiving the remote communication.

9. The method of claim 8, wherein receiving the remote communication comprises:

receiving a communication via internet, cellular, radio, or WiFi interface.

10. The method of claim 6, wherein conditioning the power factor based on conditions of the power grid further comprises:

receiving a communication from a master controller on the same side of the point of connection indicating a power factor adjustment; and

adjusting the power factor in response to receiving the communication.

11. The method of claim 6, wherein conditioning the power factor comprises:

degrading the power factor away from unity responsive to conditions of the power grid.

12. The method of claim 1, wherein conditioning the power factor comprises:

adjusting the power factor to approximately unity.

13. The method of claim 1, wherein conditioning the power factor further comprises:

conditioning the power factor of the generated AC current based on a best benefit analysis, including considering a power rate tariff set by a utility of the power grid.

14. The method of claim 1, wherein delivering the conditioned AC power further comprises:

delivering conditioned AC power to the power grid.

15. An inverter apparatus comprising:

input hardware to receive a direct current (DC) power from a local power source, the local power source and the inverter electrically located on a same side of a point of connection to a utility power grid as a local load tied to the power grid, where the local load includes a consumer premises of the power grid;

inverter hardware to convert the DC power to alternating current (AC) power to deliver to the local load, including receive characteristic shape and phase information about a target periodic waveform having a phase with respect to an AC voltage of the power grid and generate an output current waveform based on a reference output waveform representing an ideal version of the target periodic waveform based on the received characteristic shape and phase information;

power factor conditioning hardware to condition a power factor of the AC power by controlling the phase of the generated current output waveform with respect to phase of the voltage of the power grid including offsetting the reference output waveform to generate the output current waveform at a desired power factor with respect to the AC voltage of the power grid; and

output hardware to deliver the conditioned AC power on the local load side of the power grid.

16. The inverter apparatus of claim 15, wherein the power factor conditioning hardware further comprises:

a software algorithm to locally determine power factor conditioning.

17. The inverter apparatus of claim 15, further comprising:

a remote control mechanism to receive a command from a remote device providing input for determining power factor conditioning.

18. The inverter apparatus of claim 15, wherein the power factor conditioning hardware is to further generate an output current waveform with output hardware;

sample the output current waveform;

compare the output current waveform to a corresponding the reference output waveform;

generate a feedback signal based on comparing the output current waveform to the reference output waveform; and

adjust an operation of the output hardware at runtime based on the feedback signal to converge the output current waveform toward the reference output waveform and phase.