How to manipulate the frequency response of a battery

Abstract

The present disclosure relates to a computer-implemented method for operating a battery to provide a frequency response to an electric power grid, the battery including a plurality of containers configured to store electric energy, and for a given container, the method includes the steps of: determining a target response for the container by dividing a target response of the system by the plurality of containers; determining a container capacity by dividing a battery capacity by the plurality of containers; determining a state of charge offset between an average charge across the plurality of containers and the charge of the given container; determining a response adjustment by multiplying the container capacity by the state of charge offset; and adjusting the target response for the container by the response adjustment to determine the response of the given container.

Description

[Technical Field]

[0001] The present disclosure relates to the operation of batteries, and more particularly to providing frequency response to an electrical grid with batteries. [Background technology]

[0002] Due to the increasing trend toward the use of renewable energy sources (RESs) in the form of wind and solar power, power grids are increasingly required to manage variable-output renewable energy sources with intermittent output. Energy storage systems (ESSs) are sometimes integrated with grid-linked RESs and are used to manage the uncertainty and output variability of renewable energy generation, maintain secure grid operations, and meet increasing reserve requirements to balance supply and demand. ESSs can also be used independently of RESs. ESSs play an important role in storing excess generated energy and subsequently making it available during suboptimal generation conditions or peak energy demand. Improvements in energy storage technology and power electronics, coupled with these changes in the electricity market, are increasing reliance on ESSs as a cost-effective energy resource. Among ESSs, battery energy storage systems (BESSs) are one of the most suitable candidates for grid-scale applications because they provide rapid active power response and are well-suited to compensate for fluctuations generated by RESs and demand usage.

[0003] Maintaining a balance between energy demand and generation to keep the system frequency close to the nominal frequency (e.g., 50 Hz in the UK) is a key issue in power system operation and control. The nature of renewable energy generation can cause power fluctuations on the generation side or reduce system inertia, which can contribute to frequency stability issues.

[0004] Typically, a battery providing frequency response services to a system operator consists of multiple vessels. When a battery is called into service, it typically assumes a generic battery state of charge (SoC) that represents the state of charge (SoC) of each vessel in the set of vessels. As a result, when a battery needs to import (charge) or export (discharge) power, the request to import or export power from multiple vessels does not differentiate between the individual vessels.

[0005] Different battery containers can diverge in different directions, for example, due to microfailures or inefficiencies in some components (e.g., inverters or battery cells). Therefore, conventional approaches lack a mechanism for converging the state of charge of multiple battery containers to a common state of charge. This can cause one or several of the containers to reach their upper or lower limits, halting power import or export, while the battery's state of charge (i.e., the average of all containers) remains either below the upper limit or above the lower limit, resulting in an error in which one or more containers are unresponsive. Furthermore, if monitoring logic is configured to interpret the failure of one container as a failure of the entire battery (as is necessary for some services), this can result in a battery "outage" even when some containers are within their operational limits. Such outages are undesirable, can place additional strain on other elements of the system, and can incur service provider penalties for non-delivery. Furthermore, frequent outages can make the service unpredictable and unreliable, potentially disqualifying the battery from providing service.

[0006] Therefore, it is desirable to provide an improved method of operating batteries to provide frequency response to the power grid. [Brief explanation of the drawings]

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0008] [Figure 1] FIG. 1 illustrates an exemplary method for operating a battery for frequency response according to one embodiment. [Figure 2] FIG. 2 illustrates an exemplary method for determining a target response of a system. [Figure 3] FIG. 3 illustrates an exemplary method for determining the state of charge of a container. Detailed Description of the Invention

[0009] As shown in FIG. 1 , the present technology provides a computer-implemented method for operating a battery to provide frequency response to an electric power grid, where the battery includes a plurality of containers configured to store electrical energy. The method includes, for a given container, the following steps:

[0010] In S101, a target response for the vessel is determined by dividing the target response for the system by a number of vessels.

[0011] In S102, the container capacity is determined by dividing the battery capacity by the number of containers.

[0012] In S103, a state of charge offset between the average state of charge across the plurality of containers and the state of charge of a given container is determined.

[0013] In S104, the response adjustment is determined by multiplying the reservoir capacity by the state of charge offset.

[0014] In S105, a predetermined vessel response is determined by adjusting the vessel's target response with a response adjustment.

[0015] The techniques described herein enable a multi-container battery to operate efficiently based on the status of each individual container and provide effective frequency response services to the power grid by adjusting the response based on the current status of each battery container. In this way, the techniques allow the battery to operate efficiently and reduce the likelihood of an entire battery outage.

[0016] In some embodiments, a further multiplication by a factor K may be performed in S106 when determining the response adjustment.

[0017] In some embodiments, the coefficient K may be determined by the parameters of the battery.

[0018] In some embodiments, if the response of a given vessel exceeds the upper or lower limits, the coefficient K may be adjusted so that the response of the given vessel falls between the upper and lower limits.

[0019] In some embodiments, the upper limit may correspond to a condition in which a given container is fully charged, and / or the lower limit may correspond to a condition in which a given container is fully discharged.

[0020] In some embodiments, the response of a given vessel may include the rate at which the given vessel is charged or discharged, with negative values ​​of the response corresponding to charging and positive values ​​corresponding to discharging.

[0021] In some embodiments, the method may further include comparing the state of charge range of the plurality of containers to a predetermined threshold, and the state of charge range of the plurality of containers may be determined by the difference between the highest state of charge and the lowest state of charge among the plurality of containers.

[0022] In some embodiments, once the state of charge range of the plurality of containers is determined to be below a predetermined threshold, the response for all containers of the plurality of containers may be set to be the same.

[0023] In some embodiments, when a state of charge range for a plurality of containers is determined to be equal to or greater than a predetermined threshold, a response for all containers in the plurality of containers may be established using the method.

[0024] In some embodiments, the state of charge of a given container may be determined by averaging, over a predetermined period of time, multiple instantaneous state of charge values ​​for the given container measured at predetermined time intervals.

[0025] In some embodiments, the method may further include implementing a shutdown strategy for scaling the response of a given vessel in the event that one or more vessels fail.

[0026] In some embodiments, the shutdown strategy may involve adjusting the target response of the system downward in proportion to the number of functioning vessels.

[0027] In some embodiments, the method may further include setting an expected number of containers, and adjusting the target response of the system downward in proportion to the number of containers if the number of containers is found to be less than the expected number of containers.

[0028] A further aspect of the present technology provides for providing a computer readable medium containing machine readable code that, when executed by a processor, causes the processor to perform the methods described above.

[0029] A further aspect of the present technology provides a controller for operating a battery to provide a frequency response, the controller comprising at least one processor and a non-removable computer-readable medium having stored thereon software instructions, executed by the at least one processor, for determining a response for a given container by dividing battery capacity by a plurality of containers to determine a state of charge offset between a given container's state of charge and an average state of charge across the plurality of containers, multiplying the state of charge offset by the container capacity to determine a response adjustment, and adjusting a target response for the container with the response adjustment.

[0030] Each embodiment of the present technology will have at least one, but not necessarily all, of the above-described objects and / or aspects, and it will be understood that some aspects of the present technology, while attempting to achieve the above-described object, may not satisfy that object and / or may satisfy other objects not specifically set forth herein.

[0031] Additional and / or alternative features, aspects, and advantages of embodiments of the technology will become apparent from the following description, the accompanying drawings, and the appended claims.

[0032] Generally, embodiments of the present technology provide a method for determining how a battery with multiple containers operates to provide charging and frequency response for a power grid, which method is summarized as follows:

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[0033] It should be noted that if K equals 0, no correction is required. "Response" refers to the rate at which a particular reservoir of a battery is charged or discharged. In some embodiments, "Response" may also refer to the amount at which a particular reservoir of a battery is charged or discharged. When "Response" is a negative value, the particular reservoir is being charged. When "Response" is a positive value, the particular reservoir is being discharged.

[0034] Thus, according to current methods, if the state of charge of a particular container (e.g., as a percentage or fraction) is higher than the average state of charge of all the containers of the battery, the particular container is configured to be undercharged or overdischarged, whereas if the state of charge of a particular container is lower than the average state of charge of all the containers of the battery, the particular container is configured to be overcharged or overdischarged.

[0035] In some embodiments, if the method determines a response for a particular container such that the particular container exceeds an upper limit or falls below a lower limit, the coefficient K can be adjusted to adjust the value of the response so that the particular container operates within the upper and lower limits. The upper limit may correspond, for example, to a condition where the particular container is fully charged. The lower limit may correspond, for example, to a condition where the particular container is fully discharged.

[0036] In some cases, it may be preferable not to apply the current method, such as when the state of charge of each container of a battery deviates slightly from the average state of charge, making adjustments made by applying the current method insignificant or when applying the current method is inefficient. Therefore, in some embodiments, a predetermined threshold "entryDeadbandSocRange" may be set. This sets the response of each container of a battery to be the same when the range of state of charge of multiple containers is below the predetermined threshold "entryDeadbandSocRange." For example, the predetermined threshold "entryDeadbandSocRange" may be set so that the target response for the container is the target response of the system divided by the number of containers in the battery. When the range of state of charge of multiple containers exceeds the predetermined threshold "entryDeadbandSocRange," the response of each container of the battery may be adjusted to the response determined by the current method. In some embodiments, another threshold "exitDeadbandSocRange" for the range of state of charge of multiple containers may be set, above which the response of a given container may be determined by the current method. Here, the range of states of charge of the plurality of containers (state of charge range) may be determined, for example, by the difference between the highest and lowest states of charge among the plurality of containers.

[0037] In some embodiments, a time-averaged state of charge may be used as the state of charge for a particular container, as shown in Figure 2. For example, the time-averaged state of charge for a particular container may be determined by averaging multiple instantaneous state of charge values ​​for the given container measured in S201 at various times or predetermined time intervals over a predetermined time period "deviceEnergySampleFrameSeconds" in S202. Using a time-averaged state of charge smooths out the effect of the adjustment, with longer time intervals "deviceEnergySampleFrameSeconds" corresponding to smoother corrective adjustments.

[0038] The present method can be configured to evaluate the current conditions under which the battery operates to provide frequency response services. For example, it can take into account an outage declared on the grid (such as when one or more vessels fail). In some embodiments, it may be desirable to scale the response of the battery or individual vessels in the battery based on the number of vessels functioning, as shown in FIG. 3.

[0039] In some embodiments, the method may be configured to ignore one or more out-of-service containers due to charge management actions. For example, if it is determined in S301 that the number of functioning containers is less than the total number of containers, then in S302, the target response of the system may be scaled down. For example, the scale down may be proportional to the number of functioning containers. For example, if one out of five containers is out of service, the target response of the system may be scaled down to 80%. In other embodiments, the scale down may be performed using different ratios or weights.

[0040] In some embodiments, the method may be configured to ignore one or more vessels that are unable to provide service due to local withdrawal reasons (or other reasons), in which case the target response of the system may again be scaled back in proportion to the number of functioning or operational vessels at S302.

[0041] In some embodiments, a vessel number baseline or vessel number forecast is set, and if the number of vessels in operation is less than this forecasted number of vessels, the target response of the system may be scaled down, for example proportionally to the number of vessels.

[0042] The technology can efficiently operate based on the status of individual containers in a multi-container battery and provide an appropriate frequency response to the power grid by adjusting the response based on the battery's status relative to the other containers. In this way, the technology can efficiently operate the battery and reduce the likelihood of the entire battery going offline.

[0043] As will be appreciated by those skilled in the art, the technology may be embodied as a system, method, or computer program product, and thus may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware.

[0044] Furthermore, the present technology may take the form of a computer program product embodied in a computer-readable medium having computer-readable program code embodied thereon. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof.

[0045] Computer program code for carrying out operations of the present techniques may be written in any combination of one or more programming languages, including object-oriented and conventional procedural programming languages.

[0046] For example, program code for carrying out operations of the present technology may consist of source code, object code, or executable code in a conventional programming language (interpreted or compiled) such as C, assembly code, code for configuring or controlling an ASIC (application specific integrated circuit) or FPGA (field programmable gate array), or code in a hardware description language such as Verilog™ or VHDL (high-speed integrated circuit hardware description language).

[0047] The program code may execute entirely on the user's computer, partly on the user's computer and partly on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer via any type of network. The code components may be embodied as procedures, methods, etc., and may be composed of subcomponents in the form of instructions or sequences of instructions at any level of abstraction, from direct machine instructions in a native instruction set to higher-level compiled or interpreted language constructs.

[0048] It will also be apparent to those skilled in the art that the logical methods according to preferred embodiments of the present technology may be embodied in whole or in part in a logic device including logic elements for performing the steps of the method, where appropriate, and such logic elements may be comprised of elements such as logic gates in a programmable logic array or an application specific integrated circuit. Such logic arrangements may further be embodied in enabling elements for temporarily or permanently establishing the logical structure within such arrays or circuits, for example using a virtual hardware descriptor language, which elements may be stored and transmitted using a fixed or transmittable carrier medium.

[0049] The examples and conditional statements described herein are intended to help the reader understand the principles of the present technology, and are not intended to limit the scope of the present technology to the specifically described examples and conditions. Those skilled in the art will understand that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present technology and are included within the scope defined by the appended claims.

[0050] Furthermore, to aid in understanding, the above description may describe relatively simplified implementations of the technology, and those skilled in the art will appreciate that various implementations of the technology may be more complex.

[0051] In some cases, examples of useful modifications to the technology are provided. This is intended to aid understanding and is not intended to limit or delimit the scope of the technology. These modifications are not an exhaustive list, and one of ordinary skill in the art may make other modifications while remaining within the scope of the technology. Furthermore, the absence of examples of modifications should not be interpreted as meaning that modifications are impossible, and / or that the described method is the only way to implement elements of the technology.

[0052] Furthermore, all statements describing principles, aspects, and specific examples of embodiments of the present technology are intended to encompass both structural and functional equivalents, whether now known or developed in the future. Thus, for example, all block diagrams embodying the principles of the present technology will be understood by those skilled in the art to represent conceptual views of illustrative circuitry embodying the principles of the technology. Similarly, any flowcharts, flow diagrams, state transition diagrams, pseudocode, and the like will be understood to substantially illustrate processes represented on a computer-readable medium and executed by a computer or processor, whether or not such a computer or processor is explicitly shown.

[0053] The functionality of each element shown in the diagram, including the block functions labeled "processor," can be provided through the use of dedicated hardware as well as hardware capable of executing software. When provided by a processor, the functionality may be provided by a single dedicated processor, a single shared processor, or several individual processors (some of which may be shared). Furthermore, the explicit use of the terms "processor" or "controller" should not be construed as referring solely to hardware capable of executing software. This implicit term can include, but is not limited to, digital signal processor (DSP) hardware, network processors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and / or custom, may also be included.

[0054] A software module, or simply a module implied as software, may be represented as any combination of flowchart elements or other elements illustrating the execution of process steps. Such modules may be executed by explicitly or implicitly shown hardware.

[0055] It will be apparent to those skilled in the art that many modifications and variations can be made to the exemplary embodiments described above without departing from the scope of the present technology.

Claims

1. 1. A computer-implemented method for operating a battery that provides frequency response to an electric power grid, the battery comprising a plurality of containers, each configured to store electrical energy, the method comprising, for a given container: determining a target response for the container by dividing a target response of the system by the plurality of containers; determining a container capacity by dividing a battery capacity by the plurality of containers; determining a state of charge offset between an average state of charge of the plurality of containers and a state of charge of the given container; determining a response adjustment by multiplying the capacity of the container by the state-of-charge offset; determining a response for the given container by adjusting a target response for the container with the response adjustment; A method comprising:

2. The method of claim 1 , wherein determining the response adjustment further comprises multiplying by a factor K.

3. 3. The method of claim 2, wherein the coefficient K is determined by parameters of the battery.

4. 4. The method of claim 2 or 3, wherein if the response of the given container is greater than an upper limit or less than a lower limit, the coefficient K is adjusted until the resulting response of the given container is within the range between the upper limit and the lower limit.

5. 5. The method of claim 4, wherein the upper limit corresponds to a fully charged state of the given container and / or the lower limit corresponds to a fully discharged state of the given container.

6. 2. The method of claim 1, wherein the response of the given container comprises a rate at which the given container is charged or discharged, with a negative value of the response corresponding to charging and a positive value of the response corresponding to discharging.

7. 10. The method of claim 1, further comprising initially comparing a state of charge range of the plurality of containers to a predetermined threshold, wherein the state of charge range of the plurality of containers is determined by the difference between a highest state of charge and a lowest state of charge among the plurality of containers.

8. 8. The method of claim 7, wherein upon determining that the state of charge range of the plurality of containers is below the predetermined threshold, the response of all of the plurality of containers is set to be the same.

9. 9. The method of claim 7 or 8, wherein upon determining that the state of charge range of the plurality of containers is above the predetermined threshold, a response of each of the plurality of containers is set using the method.

10. 10. The method of claim 1, wherein the state of charge of the given container is determined by averaging a plurality of instantaneous state of charge values ​​for the given container measured at predetermined time intervals over a predetermined period of time.

11. The method of claim 1 , further comprising implementing a failure handling strategy that scales the response of the given container when one or more containers of the plurality fail.

12. The method of claim 11 , wherein the failure handling strategy comprises adjusting the target response of the system downward in proportion to the number of functioning containers.

13. 10. The method of claim 1, further comprising: setting an expected number of containers; and, upon determining that the plurality of containers is less than the expected number of containers, adjusting a target response of the system downward in proportion to the plurality of containers.

14. A computer readable medium comprising machine readable code which, when executed by a processor, causes the processor to perform the method of claim 1.

15. 15. The computer-readable medium of claim 14, wherein the response adjustment further comprises multiplying by a coefficient K, and if the response of the given container is greater than an upper limit value or less than a lower limit value, the coefficient K is adjusted until the resulting response of the given container is within the range of the upper limit value and the lower limit value.

16. 15. The computer-readable medium of claim 14, wherein the response of the given container comprises a rate at which the given container is charged or discharged, a negative value of the response corresponding to charging and a positive value of the response corresponding to discharging.

17. A control device for operating a battery that provides frequency response to an electric power grid, the battery comprising a plurality of containers each configured to store electrical energy; The control device at least one processor; When executed by the at least one processor, the device, for a given container of the plurality of containers, determining a target response for the container by dividing a target response of the system by the number of containers; determining a container capacity by dividing a battery capacity by the plurality of containers; determining a state of charge offset between an average state of charge of the plurality of containers and a state of charge of the given container; determining a response adjustment by multiplying the capacity of the container by the state-of-charge offset; a non-transitory computer readable medium having stored thereon software instructions for determining a response for the given container by adjusting a target response for the container with the response adjustment; A control device comprising:

18. 18. The control device of claim 17, wherein the response adjustment further comprises multiplying by a coefficient K, and if the response of the given container is greater than an upper limit value or less than a lower limit value, the coefficient K is adjusted until the resulting response of the given container is within the range of the upper limit value and the lower limit value.

19. 18. The control device of claim 17, wherein the response of the given container comprises a rate at which the given container is charged or discharged, with a negative value of the response corresponding to charging and a positive value of the response corresponding to discharging.

20. 18. The control device of claim 17, wherein the software instructions, when executed by the at least one processor, further cause the device to initially compare a state of charge range of the plurality of containers to a predetermined threshold, and determine the state of charge range of the plurality of containers by the difference between the highest state of charge and the lowest state of charge among the plurality of containers.

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