POWER TRANSFER MANAGEMENT FOR LOCAL POWER SOURCES OF A GRID-TIED LOAD

• US 20140350742A1
• Filed: 02/20/2014
• Published: 11/27/2014
• 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.
• Granted Patent: US 9,690,313 B2
• Time in Patent Office: Days
• US Class Current: 700/297
• 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;

converting with the power converter the DC power to alternating current (AC) power to deliver to the local load, including generating a reactive power component from the DC power; and

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

2. The method of claim 1, wherein generating the reactive power component comprises:

generating an AC current waveform out of phase with respect to a voltage waveform off the grid, based on a table-based phase adjustment.

3. The method of claim 1, wherein generating the reactive power component comprises:

generating the reactive power component in response to detection of a reactive power need by the local load.

4. The method of claim 1, wherein generating the reactive power component further comprises:

generating an output current waveform with output hardware;

sampling the output current waveform;

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

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

adjusting 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.

5. A method comprising:

receiving characteristic shape and phase information about a target periodic waveform;

generating an output waveform with output hardware;

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.

6. The method of claim 5, wherein the output waveform and the reference output waveform comprise an output current waveform and a reference output current waveform, respectively.

7. The method of claim 5, wherein generating the output waveform comprises:

generating the output waveform based on a pulse width modulated base waveform, the pulse width modulated base waveform created from entries in a pulse width modulator (PWM) table.

8. The method of claim 7, wherein adjusting the operation of the output hardware further comprises:

dynamically adjusting one or more entries in the PWM table during runtime based on the generated feedback signal.

9. The method of claim 5, wherein sampling the output waveform and comparing the output waveform to the reference output waveform comprises:

sampling and comparing point-by-point between the two waveforms.

10. The method of claim 5, wherein comparing the output waveform to the reference output waveform comprises:

precomputing a set of ideal sample points representing the reference output waveform prior to sampling the output waveform; and

storing the precomputed sample points.

11. The method of claim 5, wherein comparing the output waveform to the reference output waveform comprises:

comparing a sample point of the output waveform to a corresponding reference setpoint with a PID (proportional-integral-derivative) controller.

12. The method of claim 5, wherein adjusting the operation of the output hardware further comprises:

adjusting the operation of the output hardware to reduce harmonic distortion in the output waveform without performing a specific harmonic distortion analysis.

13. The method of claim 5, further comprising:

dynamically adjusting entries in a reference waveform table during runtime to dynamically adjust the reference output waveform.

14. The method of claim 5, further comprising:

shifting the output waveform in phase dynamically with respect to the target periodic waveform without increasing harmonic distortion.

15. A method comprising:

receiving, at an AC/DC power supply, alternating current (AC) power;

conditioning a power factor of the AC power by controlling a phase of current of the AC power with respect to phase of an AC voltage of the power supply, wherein controlling the phase includes adjusting the phase of the current of the AC power to be in phase with the phase of the AC voltage;

converting the conditioned AC power into direct current (DC) power; and

delivering the DC power to a load of the power supply.

16. The method of claim 15, wherein conditioning the power factor further comprises:

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