METHOD AND SYSTEM FOR PERFORMANCE MANAGEMENT OF AN ENERGY STORAGE DEVICE

• US 20140336840A1
• Filed: 12/07/2012
• Published: 11/13/2014
• Est. Priority Date: 12/09/2011
• Status: Active Grant

• Current Assignee: Fluence Energy LLC (AES Corporation)
• Original Assignee: AES Corporation
• Inventors: Geinzer, Jay Craig, Shelton, John Christopher, Galura, Brett Lance
• Granted Patent: US 10,886,742 B2
• Time in Patent Office: Days
• US Class Current: 700/297
• CPC Class Codes: G05B 11/00 Automatic controllers G05B13/00 takes precedence
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 11/00 Circuit arrangements for providing service supply to auxiliaries of stations in which electric power is generated, distributed or converted
• CPC Class Codes: H02J 2300/20 The dispersed energy generation being of renewable origin
• CPC Class Codes: H02J 3/28 Arrangements for balancing of the load in a network by storage of energy
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 70/30 Systems combining energy storage with energy generation of non-fossil origin

Abstract

Approaches for managing and maintaining a state of charge of an energy storage device by adjusting (biasing) responses to electrical grid operator commands to perform ancillary services are disclosed. In embodiments, methods and systems regulate a set point regulation in an energy system. In an embodiment, a method determines when the set point needs to be changed, calculates a new set point, and moves the output of the system from an old set point to the new set point at a defined ramp rate. The method then incorporates, as part of a set point algorithm, the capability to restore the energy storage device to a desirable state of charge (SOC). Embodiments implement Dynamic Bias, SOC and Signal Bias Range Maintaining, Operational Limits, and Fixed Signal Bias algorithms and perform Intelligent Algorithm Selection to manage and maintain the SOC of an energy storage device by biasing responses to grid operator commands.

Claims

1. A method for controlling a state of charge (SOC) of an energy storage device in an energy system, the method comprising:

determining a current SOC of the energy storage device;

receiving a polynomial bias factor in response to invoking a polynomial function;

calculating a dynamic SOC bias based on the polynomial bias factor and a difference between the current SOC and a desired SOC of the energy storage device;

controlling the SOC to be within a desired SOC range in accordance with the polynomial bias factor and the regulation signal,

wherein the polynomial function can be dynamically adjusted based on characteristics of a regulation signal of the energy system.

2. The method of claim 1, wherein the polynomial function is a 7^th order polynomial function.

3. The method of claim 2, further comprising transforming the current SOC to create a current SOC index, wherein:

the current SOC index ranges from −

1 to +1;

the polynomial bias factor ranges from −

100% to +100% of the maximum bias amount; and

the energy storage unit is;

substantially empty when the current SOC index is about −

1.0;

about half full when the current SOC index is 0; and

substantially full when the current SOC index is about 1.0.

4. The method of claim 3, further comprising:

creating a first differences score for the regulation signal ranging from 0 to 1, where a first differences score of 0 represents a regulation signal that seldom changes and a first differences score of 1 represents a regulation signal that changes by a larger amount more often;

creating a threshold score for the regulation signal ranging from 0 to 1, wherein a threshold score of 0 represents a regulation signal that is very strongly positive or negative most of the time and a threshold score of 1 represents a regulation signal that is not strongly positive or negative most of the time; and

averaging the first differences score and the threshold score to create a composite score ranging from 0 to 1, wherein a composite score of 0 represents a regulation signal that is less positive or negative most of the time and changes often, and a composite score of 0 represents a regulation signal that is very strongly positive or negative most of the time and seldom changes,

wherein the polynomial function is dynamically adjusted based on the composite score to alter the way the polynomial bias factor is calculated.

5. The method of claim 4, wherein the polynomial function is y=3.35*n*(x̂

3)−

3.35*n*(x̂

5)+(x̂

7), where;

n is the composite score; and

x=2*SOC−

1, where SOC is the current SOC of the energy storage device and the value x is the current SOC index of the energy storage device.

6. The method of claim 1, further comprising:

identifying regulation signal characteristics that may;

overheat the energy storage device;

cause the energy storage device to become full;

or

cause the energy storage device to become empty; and

dynamically adjusting the polynomial function to provide a smaller or larger polynomial bias factor, depending on the characteristics of the signal

7. The method of claim 1, wherein the energy storage device provides frequency regulation or intermittent renewable regulation services to the energy system in accordance with the regulation signal.

8. The method of claim 1, further comprising servicing the regulation signal in accordance with certain minimum technical requirements (MTRs) associated with an Independent System Operator (ISO), a Regional Transmission Organization (RTO), a power pool, or an operator of an electric grid associated with the energy system.

9. The method of claim 1, wherein the desired SOC range reflects equipment requirements for the energy storage device and

operations parameters associated with an operations plan for the energy storage device.

10. The method of claim 1, wherein the energy system supplies power to a regional power utility, a power pool, or a Regional Transmission Organization (RTO).

11. A method for adjusting a rate of change of an output of a variable energy generation source in an energy system comprising an energy storage unit, the method comprising:

calculating a state of charge (SOC) bias factor for the energy storage unit based on a current SOC of the energy storage unit and a desired SOC for the energy storage unit;

calculating a moving average output of the variable energy generation source over a time period;

calculating an indicated setpoint based on the moving average and the SOC bias factor;

receiving a ramp rate indicating desired rate of change of output for the variable generation source;

calculating a current set point based on the indicated setpoint, a unit delay of the variable energy generation source, the ramp rate, and current generation output of the variable energy generation source;

comparing the current set point to the indicated set point;

determining, based on the comparing, whether the current set point needs to be changed; and

moving the current set point toward the indicated set point at the ramp rate.

12. The method of claim 11, further comprising:

transmitting a regulation signal to the energy storage device representing the difference between the current set point and the current generation output of the variable energy generation source; and

maintaining the total output of the variable energy generation source at a fixed amount by charging or discharging the energy storage device in accordance with the regulation signal.

13. The method of claim 12, wherein the variable energy generation source is an intermittent, renewable energy resource.

14. The method of claim 13, wherein:

the variable energy generation is a wind energy resource or a solar energy resource;

the current generation output is current wind generation or current solar generation; and

the regulation signal is a wind or solar regulation signal.

15. The method of claim 11, wherein the ramp rate can be either an increase or a decrease of power output of the variable energy generation source.

16. The method of claim 11, wherein the time period for calculating the moving average is related to an energy capacity of the energy storage device such that the time period is longer for an energy storage device with a relatively high energy capacity and the time period is shorter for an energy storage device with are relatively low energy capacity.

17. The method of claim 11, further comprising updating the indicated setpoint to a combined value of the moving average and the SOC bias factor in response to determining that a difference between the combined value and the indicated set point exceeds a defined threshold value.

18. A system for controlling a state of charge (SOC) and responsiveness of an energy storage device to a regulation signal to be within specified tolerances, the system comprising:

a processor; and

a memory storing control logic, that in response to execution by the processor, causes the processor to perform operations comprising;

storing, in a storage device, 30 seconds of past regulation signals;

identifying the highest and lowest values over those 30 seconds;

calculating a range between the highest and lowest values; and

selecting the highest of a current regulation signal or the highest value minus 10% of the range.

19. The system of claim 18, wherein the specified tolerance of the SOC of the energy storage device comprises a plurality of bands of SOC values including:

SOC values greater than 97%;

SOC values greater than 55% and less than or equal to 97%;

SOC values greater than 45% and less than or equal to 55%;

SOC values greater than 3% and less than or equal to 45%; and

SOC values less than or equal to 3%.

20. The system of claim 18, wherein the specified tolerance is one or more of:

a function of a value of the regulation signal; and

an amount of time it takes for the energy storage device to respond to the regulation signal.

21. A non-transitory computer readable storage medium having instructions stored thereon that, in response to execution by a computing device, cause the computing device to perform operations for maintaining a state of charge (SOC) for an energy storage device supplying power to an electric grid, the operations comprising:

determining a maximum allowed average deviation from a regulation signal associated with the electric grid;

in response to determining that the SOC of the energy storage device is above a maximum SOC limit;

setting an SOC bias amount equal to or slightly less than a maximum SOC bias amount; and

adding the SOC bias amount to the regulation signal; and

in response to determining that the SOC is equal to or below a minimum SOC limit, setting the SOC bias amount to zero,

wherein the maximum SOC bias amount is;

a maximum allowed average deviation according to a minimum technical requirement (MTR) of an operator of the electric grid;

or

less than a maximum allowed deviation according to an MTR in order to cover system deviations due to auxiliary load and other factors.

22. The non-transitory computer readable storage medium of claim 21, wherein the maximum and minimum SOC limits are adjustable.

23. The non-transitory computer readable storage medium of claim 21, wherein the maximum SOC limit is 55% and the minimum SOC limit is 45%.

24. The non-transitory computer readable storage medium of claim 21, wherein the operator of the electric grid is an Independent System Operator (ISO) or a Regional Transmission Organization (RTO).

25. A system for controlling a state of charge (SOC) of an energy storage device configured to supply power to an electric grid, the system comprising:

at least one power generator configured to generate power, the at least one power generator being connected to the electric grid and being coupled to the energy storage device;

an SOC receiver configured to receive indications of a current SOC and a desired SOC of the energy storage device;

an SOC bias calculator configured to calculate an SOC bias based at least on a regulation signal and a difference between the current SOC and the desired SOC;

a controller configured to adjust, based on the SOC bias, the SOC of the energy storage device to be within a desired SOC range.

26. A non-transitory computer readable storage medium having instructions stored thereon that, in response to execution by a computing device, cause the computing device to perform operations for controlling a state of charge (SOC) of an energy storage device configured to supply power to an electric grid, the operations comprising:

determining a current SOC of the energy storage device;

receiving an indication of a desired SOC of the energy storage device;

calculating an SOC bias based at least on a difference between the current SOC and the desired SOC;

adjusting, based on the SOC bias and in accordance with a regulation signal, the SOC of the energy storage device to be within a desired SOC range.

27. The non-transitory computer readable storage medium of claim 26, wherein the regulation signal is received from an operator of the electric grid.