Method and Apparatus for Controlling a Hybrid Power System

• US 20110273022A1
• Filed: 07/19/2011
• Published: 11/10/2011
• Est. Priority Date: 01/16/2009
• Status: Active Grant

• Current Assignee: Faith Technologies Incorporated (Faith Group Co.)
• Original Assignee: EnSync, Inc.
• Inventors: Vang, Der, Raasch, Michael, Dennis, Kevin
• Granted Patent: US 9,093,862 B2
• Time in Patent Office: Days
• US Class Current: 307/72
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• 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 2300/28 The renewable source being wind energy wind motors F03D
• 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 3/388 Islanding, i.e. disconnection of local power supply from the network
• CPC Class Codes: H02J 3/42 with automatic parallel connection when synchronisation is achieved
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• 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
• CPC Class Codes: Y02P 80/20 using renewable energy

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. The converter selectively transfers energy to the DC bus at a maximum rate or at a reduced rate according to the level of the DC voltage present on the DC bus. At least one storage device is preferably connected to the common DC bus through a power regulator. The power regulator selectively transfers energy to or from the DC bus as a function of DC voltage level present on the DC bus. Further, an inverter may be provided to bidirectionally convert between the DC voltage and an AC voltage for connection to a customer load or the utility grid. Each power conversion device is independently controlled to provide a modular and simplified power control system.

Claims

1. A power control system for managing energy transfer, the power control system comprising:

a common DC bus;

a plurality of energy storage devices; and

a plurality of energy regulators, each energy regulator having a first connection electrically coupled to at least one of the energy storage devices and a second connection electrically coupled to the common DC bus, wherein each energy regulator further comprises;

a plurality of switches, each switch selectively energized according to a switching signal, wherein the plurality of switches control energy transfer between the first and the second connections;

a voltage signal corresponding to an amplitude of a DC voltage present on the DC bus;

a memory device storing at least a control program, a low voltage setpoint, and a high voltage setpoint; and

a processor executing the control program to generate the switching signals for each of the plurality of switches as a function of the voltage signal, the low voltage setpoint, and the high voltage setpoint, wherein energy is transferred from the common DC bus to the energy storage devices if the voltage signal is greater than the high voltage setpoint and energy is transferred from the energy storage devices to the common DC bus if the voltage signal is less than the low voltage setpoint.

2. The power control system of claim 1 further comprising

at least a first and a second energy storage device;

and

at least a first and a second energy regulator corresponding to each of the first and the second energy storage devices, respectively, wherein

at least one of the low voltage setpoint and the high voltage setpoint of the first energy regulator is different than the respective low voltage setpoint or high voltage setpoint of the second energy regulator.

3. The power control system of claim 2 wherein the first energy storage device is of different construction than the second energy storage device and each of the low voltage setpoint and the high voltage setpoint for both the first energy regulator and the second energy regulator is a function of the construction of the first energy storage device and the second energy storage device, respectively.

4. The power control system of claim 1 further comprising a central controller in communication with each of the energy regulators having a processor configured to execute a stored program and a memory device storing at least the program and a copy of each of the voltage setpoints for the energy regulators.

5. The power control system of claim 4 wherein the central controller is configured to periodically execute the stored program on the processor to exchange the low voltage setpoint and the high voltage setpoint of a first energy regulator with the low voltage setpoint and the high voltage setpoint of a second energy regulator.

6. The power control system of claim 4 wherein the central controller is configured to periodically execute the stored program on the processor to:

load a new value into each of the low voltage setpoint and the high voltage setpoint of a first of the energy regulators, wherein each of the new values is greater than the high voltage setpoint of each of the other energy regulators;

receive a signal corresponding to a first energy storage device connected to the first energy regulator being discharged; and

resetting the value of each of the low voltage setpoint and the high voltage setpoint of the first energy regulator to their original operating value.

7. The power control system of claim 1 further comprising:

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

a plurality of switches, each switch selectively energized according to a switching signal, wherein the plurality of switches control energy transfer between the input and the output;

a voltage signal corresponding to the amplitude of the DC voltage present on the DC bus;

a memory device storing at least a control program and a mode select setpoint; and

a processor executing the control program to generate the switching signals to transfer energy from the input to the output as a function of the voltage signal and the mode select setpoint.

8. The power control system of claim 7 wherein the processor executes the control program in a first operating mode to transfer a maximum amount of energy generated by the source to the DC bus if the DC voltage signal is less than the mode select setpoint, and the processor executes the control program in a second operating mode to transfer energy generated by the source to the DC bus at a reduced rate if the DC voltage signal is greater than the mode select setpoint.

9. The power control system of claim 8 wherein the rate at which the energy generated by the source is transferred to the DC bus is a function of the difference between the voltage signal and the mode select setpoint.

10. A method for managing energy transfer between a plurality of energy storage devices connected by a common DC bus, comprising the steps of:

connecting a plurality of energy regulators to the common DC bus, each energy regulator having a first connection electrically coupled to at least one of the energy storage devices and a second connection electrically coupled to the common DC bus;

receiving a signal corresponding to an amplitude of a DC voltage present on the common DC bus at a processor executing in each energy regulator;

at each energy regulator, comparing the DC voltage signal to a low voltage setpoint and a high voltage setpoint, each of the low voltage setpoint and the high voltage setpoint being stored in a memory device in the energy regulator;

transferring energy between each energy regulator and the DC bus independently of the other energy regulators, wherein each energy regulator transfers energy from the common DC bus to the connected energy storage device if the DC voltage signal is greater than the high voltage setpoint and each energy regulator transfers energy from the connected energy storage device to the common DC bus if the voltage signal is less than the low voltage setpoint.

11. The method of claim 10 further comprising the initial step of configuring each of the low voltage setpoint and the high voltage setpoint in at least a first and a second energy regulator, wherein at least one of the low voltage setpoint and the high voltage setpoint of the first energy regulator is different than the respective low voltage setpoint or high voltage setpoint of the second energy regulator.

12. The method of claim 11 further comprising the initial step of configuring the low voltage and high voltage setpoints in each of the energy regulators.

13. The method of claim 11 further comprising the step of exchanging, at a periodic interval, the low voltage setpoint and the high voltage setpoint of a first energy regulator with the low voltage setpoint and the high voltage setpoint of a second energy regulator.

14. The method of claim 11 further comprising the steps of:

loading, at a periodic interval, a new value into each of the low voltage setpoint and the high voltage setpoint of a first of the energy regulators, wherein each of the new values is greater than the high voltage setpoint of at least one of the other energy regulators;

receive a signal corresponding to a first energy storage device connected to the first energy regulator being discharged; and

resetting the value of each of the low voltage setpoint and the high voltage setpoint of the first energy regulator to their original operating value.

15. The method of claim 14 further comprising the initial step of scheduling each of the energy regulators to periodically execute the steps of claim 14 such that only one of the energy regulators executes the steps of claim 14 at a time.

16. The method of claim 10 further comprising the steps of:

connecting at least one energy converter to the common DC bus, each energy converter having an input electrically coupled to a power generating source and an output electrically coupled to the common DC bus;

receiving a signal corresponding to the amplitude of the DC voltage present on the common DC bus at a processor executing in each energy converter; and

transferring energy between each energy converter and the DC bus independently of the other energy converters and independently of the energy regulators.

17. The method of claim 16 wherein each energy converter transfers energy between the power generating source and the DC bus in a first operating mode to transfer a maximum amount of energy generated by the source to the DC bus if the DC voltage signal is less than a mode select setpoint, and the processor executes the control program in a second operating mode to transfer energy generated by the source to the DC bus at a reduced efficiency if the DC voltage signal is greater than the mode select setpoint.

18. A power control system for managing energy transfer between at least one energy source and at least one load, the power control system comprising:

a common DC bus;

at least one energy converter further comprising;

an input electrically coupled to one of the energy sources,

an output electrically coupled to the common DC bus, and

a voltage signal corresponding to an amplitude of the voltage present on the common DC bus, wherein each energy converter is configured to transfer energy from the energy source to the common DC bus as a function of the voltage signal; and

an inverter further comprising;

a first connection electrically coupled to the common DC bus,

a second connection connected to a utility grid, and

a voltage signal corresponding to an amplitude of the voltage present on the common DC bus, wherein the inverter is configured to selectively transfer energy bidirectionally between the common DC bus and the utility grid as a function of the voltage signal, a high voltage setpoint, and a low voltage setpoint.

19. The power control system of claim 18 further comprising:

at least one energy storage device; and

at least one energy regulator further comprising;

a first connection electrically coupled to one of the energy storage devices,

a second connection electrically coupled to the common DC bus, and

a voltage signal corresponding to an amplitude of the voltage present on the common DC bus, wherein the energy regulator is configured to selectively transfer energy bidirectionally between the common DC bus and the energy storage device as a function of the voltage signal, a low voltage setpoint, and a high voltage setpoint.

20. The power control system of claim 19 further comprising a central interface storing a copy of each of the setpoints and having a user interface to permit an operator to configure each of the setpoints, wherein the central interface further comprises a processor configured to execute a stored program to periodically reconfigure at least one of the setpoints.