Method and apparatus for controlling a hybrid power system

• US 8,008,808 B2
• Filed: 01/16/2009
• Issued: 08/30/2011
• Est. Priority Date: 01/16/2009
• Status: Active Grant

• Current Assignee: Faith Technologies Incorporated (Faith Group Co.)
• Original Assignee: ZBB Energy Corporation
• Inventors: Seeker, Steven, Dennis, Kevin, Hughes, Mike
• Primary Examiner(s): RUTLAND WALLIS, MICHAEL
• Application Number:
  US12/355,169
• Publication Number:
  US 20100181837A1
• Time in Patent Office: 956 Days
• Field of Search: 307/64, 307/72
• US Class Current: 307/72
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 2300/20 The dispersed energy generation being of renewable origin
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy wind motors F03D
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 2300/40 wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/466 Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects

Abstract

The present invention provides a simplified method of controlling power among the various sources and loads in a power system. Power generating sources are each connected to a common DC bus through a converter designed to optimize power flow to the DC bus. A DC storage device is connected to the common DC bus through a power regulator designed to maintain a constant voltage on the DC bus. Further, an inverter may be provided to convert the DC voltage to an AC voltage for a customer load or for connection to the utility grid. Each power conversion device is independently controlled to provide a modular and simplified power control system.

Claims

1. A power controller for a hybrid power system comprising:

a common DC bus;

at least one energy converter having an input electrically coupled to an electrical energy generating device and an output electrically coupled to the common DC bus, each energy converter further comprising;

an input configured to receive a voltage signal corresponding to an amplitude of a DC voltage present on the DC bus, and

a control unit configured to convert energy independently of the other converters and to disable power flow from the electrical energy generating device when the amplitude of the DC voltage exceeds a predetermined maximum value;

at least one DC energy storage device;

an energy regulator having a first terminal electrically coupled to the DC energy storage device and a second terminal electrically coupled to the DC bus,

wherein the energy regulator further comprises;

an input configured to receive a voltage signal corresponding to the amplitude of the DC voltage present on the DC bus, and

a control unit configured to convert energy independently of the converters and to maintain the amplitude of the DC voltage at a substantially constant value.

2. The power controller of claim 1 wherein the at least one DC energy storage device is a regenerative fuel cell.

3. The power controller of claim 1 further comprising an inverter electrically coupled to the DC bus to convert the DC voltage to an AC voltage.

4. The power controller of claim 3 wherein the inverter supplies power to an AC load independent of a utility grid.

5. The power controller of claim 3 wherein the inverter is connected to the utility grid and supplies power to one of the grid, an AC load, or a combination thereof.

6. The power controller of claim 5 wherein the inverter provides bidirectional power flow.

7. The power controller of claim 1 wherein the electrical energy generating device is one of a wind, photovoltaic, hydroelectric, biofuel, tidal, or biomass generating source.

8. The power controller of claim 1 wherein a DC load is coupled to the DC bus.

9. The power controller of claim 1 wherein the control unit of the regulator further comprises:

a processor configured to provide a plurality of control signals as a function of the amplitude of the DC voltage;

a memory device to store a program capable of execution on the processor;

a power conversion section receiving the control signals from the processor to transfer energy either from the storage device to the DC bus or from the DC bus to the storage device to maintain the amplitude of the DC voltage on the DC bus at a substantially constant value.

10. The power controller of claim 1 wherein the control unit of the converter further comprises:

a processor configured to provide a plurality of control signals;

a memory device to store a program capable of execution on the processor;

a power conversion section receiving the control signals from the processor to convert electrical energy from the generating device to the DC voltage on the DC bus.

11. The power controller of claim 1 wherein at least one of an additional energy converter coupled to an additional electrical energy generator may be coupled to the DC bus without modifying any of the existing energy converters or the energy regulator.

12. A power controller for a hybrid power system comprising:

a common DC bus;

at least one energy converter electrically coupled between an electrical energy generating device and the common DC bus wherein the energy converter further comprises;

a first voltage signal indicating a DC voltage level present on the DC bus, and

a first control unit executing independently of other control units to regulate power flow from the energy generating device to the DC bus while the DC voltage level is below a predetermined maximum value and to disable power flow from the energy generating device when the DC voltage level is above a predetermined maximum value;

at least one DC energy storage device; and

at least one energy regulator electrically coupled between each DC energy storage device and the common DC bus wherein each energy regulator further comprises;

a second voltage signal indicating the DC voltage level present on the DC bus, and

a second control unit executing independently of other control units to maintain the DC voltage level at a substantially constant value.

13. The power controller of claim 12 further comprising an inverter electrically coupled between the DC bus and an AC grid to convert the DC voltage to an AC voltage wherein the inverter includes a third voltage signal indicating the DC voltage level present on the DC bus and a third control unit selectively provides bidirectional power flow between the DC bus and the AC grid.

14. The power controller of claim 13 wherein a single voltage sensor provides each of the first, second and third voltage signals.

15. A method of regulating power flow between a plurality of components connected by a common DC bus in a hybrid power system comprising the steps of:

providing at least one energy converter, each energy converter having a first DC voltage signal and a first control unit configured to couple an electrical energy generating source to the DC bus independently of the other energy converters;

monitoring a DC voltage present on the DC bus with the first DC voltage signal;

converting electrical energy generated by each generating source to a DC voltage and a DC current suitable for connection to the DC bus with the corresponding energy converter when the monitored DC voltage is less than a predetermined maximum value;

providing an energy regulator having a second DC voltage signal and a second control unit configured to couple a DC electrical energy storage device to the DC bus;

monitoring the DC voltage present on the DC bus with the second voltage signal; and

regulating the DC voltage to a substantially constant value with the second control unit independently of the operation of the energy converters.

16. The method of claim 15 further comprising the steps of:

providing an inverter, the inverter having a third DC voltage signal and a third control unit configured to couple the DC bus to an AC voltage grid;

monitoring the DC voltage present on the DC bus with the third DC voltage signal; and

converting voltage from either DC to AC or AC to DC with the inverter.