Method and apparatus for controlling a hybrid power system

• US 9,093,862 B2
• Filed: 07/19/2011
• Issued: 07/28/2015
• Est. Priority Date: 01/16/2009
• Status: Active Grant

• Current Assignee: Faith Technologies Incorporated (Faith Group Co.)
• Original Assignee: ZBB Energy Corporation
• Inventors: Dennis, Kevin, Raasch, Michael, Vang, Der
• Primary Examiner(s): CAVALLARI, DANIEL J
• Application Number:
  US13/185,862
• Publication Number:
  US 20110273022A1
• Time in Patent Office: 1,470 Days
• Field of Search: 307/82
• US Class Current: 1/1
• 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 first electrical energy storage device operatively connected to the common DC bus;

a second electrical energy storage device operatively connected to the common DC bus;

a first electrical energy regulator having a first connection electrically coupled to the first electrical energy storage device and a second connection electrically coupled to the common DC bus;

a second electrical energy regulator having a first connection electrically coupled to the second electrical energy storage device and a second connection electrically coupled to the common DC bus;

wherein each of the first and the second electrical 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 common 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 first electrical energy storage device if the voltage signal is greater than the high voltage setpoint of the first electrical energy regulator,

energy is transferred from the first electrical energy storage device to the common DC bus if the voltage signal is less than the low voltage setpoint of the first electrical energy regulator,

energy is transferred from the common DC bus to the second electrical energy storage device if the voltage signal is greater than the high voltage setpoint of the second electrical energy regulator,

energy is transferred from the first electrical energy storage device to the common DC bus if the voltage signal is less than the low voltage setpoint of the second electrical energy regulator,

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

2. The power control system of claim 1 wherein the first electrical energy storage device is selected from one of a battery, a flow battery, and a fuel cell and the second electrical energy storage device is selected from one of a battery, a flow battery, and a fuel cell, wherein the first energy storage device is different 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 selection of the first electrical energy storage device and the second electrical energy storage device, respectively.

3. 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.

4. The power control system of claim 3 further comprising:

a first set of voltage setpoints, including a low voltage setpoint and a high voltage setpoint, stored in the memory device of the central controller;

a second set of voltage setpoints, including a low voltage setpoint and a high voltage setpoint, stored in the memory device of the central controller, wherein the central controller is configured to execute in a first mode and a second mode, wherein;

during the first mode the central controller sets the low voltage and high voltage setpoints of the first electrical energy regulator to the first set of voltage setpoints and the low voltage and high voltage setpoints of the second electrical energy regulator to the second set of voltage setpoints,

during the second mode the central controller sets the low voltage and high voltage setpoints of the first electrical energy regulator to the second set of voltage setpoints and the low voltage and high voltage setpoints of the second electrical energy regulator to the first set of voltage setpoints, and

the central controller periodically executes the stored program on the processor to switch between the first mode and the second mode.

5. The power control system of claim 3 further comprising:

a first set of voltage setpoints, including a low voltage setpoint and a high voltage setpoint, stored in the memory device of the central controller;

a second set of voltage setpoints, including a low voltage setpoint and a high voltage setpoint, stored in the memory device of the central controller;

a third set of voltage setpoints, including a low voltage setpoint and a high voltage setpoint, stored in the memory device of the central controller, wherein each of the low voltage setpoint and the high voltage setpoint for the third set of voltage setpoints is greater than the high voltage setpoint of both the first and second sets of voltage setpoints;

wherein the central controller is configured to execute in a first mode and a second mode, wherein;

during the first mode the central controller sets the low voltage and high voltage setpoints of the first electrical energy regulator to the first set of voltage setpoint and the low voltage and high voltage setpoints of the second electrical energy regulator to the second set of voltage setpoints, and

during the second mode the central controller sets the low voltage and high voltage setpoints of one of the first electrical energy regulator and the second electrical energy regulator to the third set of voltage setpoints.

6. 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.

7. The power control system of claim 6 wherein:

the control program stored on the memory device of each energy converter includes a first operating mode and a second operating mode, wherein the first operating mode transfers a maximum amount of energy generated by the source to the DC bus and the second operating mode reduces the amount of energy transferred between the source and the DC bus as a function of the DC voltage signal,

the processor executes the control program in the first operating mode when the DC voltage signal is less than the mode select setpoint, and

the processor executes the control program in the second operating mode when the DC voltage signal is greater than the mode select setpoint.

8. A method for managing energy transfer between a first electrical energy storage devices, a second electrical energy storage device, and a common DC bus using a first electrical energy regulator and a second electrical energy regulator, wherein the first electrical energy regulator has a first connection electrically coupled to the first electrical energy storage devices and a second connection electrically coupled to the common DC bus and the second electrical energy regulator has a first connection electrically coupled to the second electrical energy storage device and a second connection electrically coupled to the common DC bus, the method comprising the steps of:

receiving a signal corresponding to an amplitude of a DC voltage present on the common DC bus at a processor in each of the first and the second electrical energy regulators;

generating a switching signal for each of a plurality of switches in each of the first and the second electrical energy regulators with the processor as a function of the voltage signal, wherein the plurality of switches in each of the first and the second electrical energy regulators control energy transfer between the first connection and the second connection of the corresponding energy regulator;

transferring energy from the common DC bus to the first electrical energy storage devices via the first electrical energy regulator when the voltage signal is greater than a high voltage setpoint in the first electrical energy regulator;

transferring energy from the first electrical energy storage device to the common DC bus via the first electrical energy regulator when the voltage signal is less than a low voltage setpoint in the first electrical energy regulator;

transferring energy from the common DC bus to the second electrical energy storage device via the second electrical energy regulator when the voltage signal is greater than a high voltge setpoint in the second electrical energy regulator; and

transferring energy from the second electrical energy storage device to the common DC bus via the second electrical energy regulator when the voltage signal is less than a low voltage setpoint in the second electrical energy regulator, wherein at least one of the low voltage setpoint and the high voltage setpoint of the first electrical energy regulator is different than the corresponding low voltage setpoint and high voltage setpoint of the second electrical energy regulator.

9. The method of claim 8 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 in each energy converter;

transferring energy between the power generating source and the common DC bus in a first operating mode to transfer a maximum amount of energy generated by the power generating source to the DC bus when the DC voltage signal is less than a mode select setpoint; and

transferring energy between the power generating source and the common DC bus in a second operating mode to transfer a portion of the energy generated by the power generating source to the DC bus when the DC voltage signal is greater than the mode select setpoint, wherein the portion decreases as the DC voltage signal increases above the mode select setpoint.

10. A method for managing energy transfer between a plurality of energy storage devices and a common DC bus using plurality energy regulators, wherein each energy regulator has 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, the method comprising the steps of:

configuring each of a low voltage setpoint and a 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;

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

generating a switching signal for each of a plurality of switches in each energy regulator with the processor as a function of the voltage signal, wherein the plurality of switches in each energy regulator control energy transfer between the first connection the second connection of the corresponding energy regulator;

transferring energy from the common DC bus to the energy storage devices when the voltage signal is greater than the high voltage set point;

transferring energy from the energy storage device to the common DC bus when the voltage signal is less than the low voltage setpoint; and

exchanging, at a periodic interval, the low voltage setpoint and the high voltage setpoint of the first energy regulator with the low voltage setpoint and the high voltage setpoint of the second energy regulator.

11. A method for managing energy transfer between a plurality of energy storage devices and a common DC bus using a plurality of energy regulators, wherein each energy regulator has 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, the method comprising the steps of:

configuring each of a low voltage setpoint and a 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;

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

generating a switching signal for each of a plurality of switches in each energy regulator with the processor as a function of the voltage signal, wherein the plurality of switches in each energy regulator control energy transfer between the first connection and the second connection of the corresponding energy regulator;

transferring energy from the common DC bus to the energy storage devices when the voltage signal is greater than the high voltage setpoint;

transferring energy from the energy storage devices to the common DC bus when the voltage signal is less than the low voltage setpoint; and

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;

receiving 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.

12. The method of claim 11 further comprising the initial step of scheduling each of the plurality of energy regulators to periodically execute the steps of claim 11 such that only one of the energy regulators executes the steps of claim 11 at a time.