Energy storage SOC equalization method applied to distributed optical storage system and optical storage system

Abstract

The invention relates to the technical field of new energy storage control, in particular to an energy storage SOC balancing method applied to a distributed optical storage system and the optical storage system. The method comprises the steps that the overall energy storage expected power of the optical storage system, the SOC of each energy storage unit and the expected power range are acquired, and power constraint conditions are defined; based on the overall energy storage expected power, the SOC of each energy storage unit and the expected power range, determining a working energy storage unit from each energy storage unit; the overall energy storage expected power is distributed to the working energy storage units, and the initial expected power of each working energy storage unit is obtained; and iteratively executing a power derating redistribution step until a power distribution termination condition is met, and obtaining the expected output power of each energy storage unit. According to the invention, SOC dynamic balance of the energy storage unit can be realized.

Description

Technical Field

[0001] This application relates to the field of new energy storage control technology, and in particular to a method for SOC equalization of energy storage systems and a photovoltaic storage system applied to distributed photovoltaic storage systems. Background Technology

[0002] In string-type distributed energy storage systems, factors such as battery aging, uneven output of the PCS (Power Conversion System), and the influence of ambient temperature lead to inconsistent SOC (State of Charge) among multiple energy storage units. Related technologies employ traditional master-slave control strategies, resulting in rigid power distribution mechanisms under derating conditions and a lack of system-level SOC coordination control. This prevents dynamic SOC balancing and increases the risk of battery overcharging / over-discharging. Summary of the Invention

[0003] To address the problem that existing technologies cannot achieve dynamic SOC balancing of energy storage units, this application provides an energy storage SOC balancing method and a photovoltaic storage system applicable to distributed photovoltaic storage systems.

[0004] Firstly, this application provides a method for energy storage SOC equalization applied to distributed photovoltaic energy storage systems, employing the following technical solution: A method for equalizing the state of energy storage (SOC) in a distributed photovoltaic-storage system includes: Obtain the overall expected energy storage power of the photovoltaic-storage system, the SOC and expected power range of each energy storage unit, and define the power constraints. Based on the overall expected energy storage power, the SOC and expected power range of each energy storage unit, the working energy storage unit is determined from the various energy storage units; The overall desired energy storage power is allocated to the working energy storage units to obtain the initial desired power of each working energy storage unit; the power derating and redistribution step is iteratively executed until the power allocation termination condition is met to obtain the desired output power of each energy storage unit. The power derating and redistribution step, using the working energy storage unit as the current energy storage unit, includes: dividing the current energy storage unit into drated energy storage units and non-drated energy storage units; adjusting the current expected power of the drated energy storage unit based on its current expected power and expected power range to complete the power derating, and determining the difference power based on the power constraint conditions; allocating the difference power to the non-drated energy storage unit; and updating the non-drated energy storage unit as the current energy storage unit.

[0005] By adopting the above technical solution, key parameters of the photovoltaic-storage system are obtained and power constraints are defined, providing a foundation and standard for subsequent operations and ensuring reasonable and legal power allocation. Based on the obtained parameters, working energy storage units are determined, accurately screening units that can participate in power allocation, avoiding ineffective participation, and improving system operating efficiency. The overall power is allocated to the working energy storage units to obtain the initial expected power, providing an initial value for power balance adjustment. By iteratively executing the power derating and redistribution steps, the power of dated and non-dated energy storage units is continuously adjusted, gradually achieving reasonable power redistribution, ultimately ensuring that the expected output power of each energy storage unit meets system requirements, achieving SOC balance of energy storage units, and improving the stability and reliability of the photovoltaic-storage system.

[0006] In a preferred embodiment, this application can be further configured as follows: determining the working energy storage unit from the various energy storage units based on the overall expected energy storage power, the SOC of each energy storage unit, and the expected power range of each energy storage unit includes: Calculate the maximum SOC difference based on the SOC of each energy storage unit; Substitute the maximum SOC difference into the equalization start-stop segmentation function. When the maximum SOC difference exceeds the equalization start threshold, the equalization algorithm is started. Arrange the energy storage units in descending order of their corresponding SOC to obtain an energy storage unit list; Based on the overall expected energy storage power and the expected power range of each energy storage unit, the system energy storage charging and discharging state is identified; based on the system energy storage charging and discharging state, the working energy storage unit that can meet the overall expected energy storage power is determined from among the various energy storage units.

[0007] By adopting the above technical solution, the maximum SOC difference of each energy storage unit is calculated to measure the degree of SOC difference and provide a basis for whether to start balancing. Substituting this into the balancing start-stop piecewise function, the balancing algorithm is started when the start threshold is exceeded, which can avoid unnecessary balancing operations and save system resources. The energy storage units are arranged into a list according to SOC from largest to smallest. The charging and discharging state of the system's energy storage is identified. Combining the overall expected power of energy storage and the expected power range of each unit, the working energy storage units that can meet the power requirements and fit the current charging and discharging state can be accurately selected.

[0008] In a preferred embodiment, this application can be further configured as follows: the desired power range includes an upper limit and a lower limit of desired power, and any working energy storage unit is taken as the target energy storage unit; the overall desired energy storage power is allocated to the working energy storage units to obtain the initial desired power of each working energy storage unit, including: Obtain the charging and discharging status of the system's energy storage; When the system energy storage is in the discharge state, the product of the SOC of each energy storage unit and the upper limit of the expected power is calculated as a first value, and the sum of the first values ​​of the working energy storage units is calculated as a second value; the ratio of the first value and the second value of the target energy storage unit is calculated as a first ratio, and the product of the first ratio and the overall expected power of energy storage is calculated as the initial expected power of the target energy storage unit. When the system's energy storage charging and discharging state is in the charging state, the product of the discharge depth and the lower limit of the expected power of each energy storage unit is calculated as a third value, and the sum of the third values ​​of the working energy storage units is calculated as a fourth value; the ratio of the third value and the fourth value of the target energy storage unit is calculated as a second ratio, and the product of the second ratio and the overall expected power of energy storage is calculated as the initial expected power of the target energy storage unit.

[0009] By adopting the above technical solution, the charging and discharging status of the system energy storage is obtained. In the discharging state, the power is allocated according to the ratio of the product of the energy storage unit's SOC and the expected power limit, which allows units with higher SOC and larger power limits to undertake more discharging tasks and make full use of their current energy storage capacity. In the charging state, the power is allocated according to the ratio of the product of the depth of discharge and the expected power limit, which allows units with a large depth of discharge and a reasonable power limit to be charged first, thus balancing the status of each energy storage unit.

[0010] In a preferred embodiment, this application can be further configured as follows: adjusting the current expected power of the derating energy storage unit based on the current expected power and expected power range of the derating energy storage unit to complete the power derating includes: For any derating energy storage unit, the current expected power of the derating energy storage unit is compared with the expected power range of the derating energy storage unit; If the current expected power of the derating energy storage unit is not higher than the lower limit of the expected power, then the current expected power of the derating energy storage unit is adjusted to the lower limit of the expected power. If the current expected power of the derating energy storage unit is not lower than the upper limit of the expected power, then the current expected power of the derating energy storage unit will be adjusted to the upper limit of the expected power.

[0011] By adopting the above technical solution, the current expected power of the derated energy storage unit is compared with its expected power range, which can accurately locate the current power within a reasonable range. If the current expected power is not higher than the lower limit of the expected power, it is adjusted to the lower limit of the expected power to avoid the power being too low and affecting the normal operation of the energy storage unit, thus ensuring its basic operating capability. If the current expected power is not lower than the upper limit of the expected power, it is adjusted to the upper limit of the expected power to prevent the power from being too high and exceeding the capacity of the energy storage unit, thus ensuring its safe and stable operation. Through such adjustments, the power is effectively controlled within a reasonable range, realizing the standardized operation of power derated.

[0012] In a preferred embodiment, this application can be further configured such that: the power constraint conditions include upper and lower limit constraints for the energy storage unit and power conservation constraints; the definition of the power constraint conditions includes: The upper and lower limit constraints of the energy storage unit are defined as follows: the expected power of each energy storage unit in the photovoltaic energy storage system does not exceed the corresponding expected power range. The power conservation constraint is defined as follows: the sum of the expected power of all energy storage units in the photovoltaic-energy storage system is equal to the overall expected energy storage power.

[0013] By adopting the above technical solutions, upper and lower limit constraints are defined for energy storage units to ensure that the expected power of each energy storage unit is within a reasonable range, preventing damage to equipment due to excessive power or ineffective energy storage due to insufficient power, thus ensuring the safety and stability of the energy storage unit's operation. Furthermore, power conservation constraints are defined to ensure that the sum of the expected power of all energy storage units is equal to the overall expected power of the energy storage system, guaranteeing the overall power balance of the photovoltaic-energy storage system. This allows the system to accurately allocate and regulate power according to demand, improving the reliability and coordination of system operation.

[0014] In a preferred embodiment, this application can be further configured as follows: dividing the current energy storage unit into dated energy storage units and non-dated energy storage units includes: The current expected power of each energy storage unit in the current energy storage unit is compared with the corresponding expected power range. The energy storage unit whose current expected power exceeds the corresponding expected power range is identified as a drated energy storage unit, and the energy storage unit whose current expected power does not exceed the corresponding expected power range is identified as a non-drated energy storage unit. Adjust the operating flags of the derated energy storage unit.

[0015] By adopting the above technical solution, the current expected power of the current energy storage unit is compared with the expected power range, which can accurately identify energy storage units with abnormal power and classify them as drated energy storage units. This allows for timely control of units with excessive power, preventing damage caused by unreasonable power operation. Units with normal power are classified as non-drated energy storage units, ensuring the continuous and stable operation of normal units. Furthermore, adjusting the operation flags of drated energy storage units can clearly mark these abnormal units, facilitating subsequent targeted adjustments and handling of their power.

[0016] In a preferred embodiment, this application can be further configured such that: the iterative execution of the power derating and redistribution step, until the power allocation termination condition is met, to obtain the desired output power of each energy storage unit, includes: In the power derating and redistribution step, if the sum of the operating flags of the current energy storage unit does not change during the current iteration, or if the differential power is less than a preset differential power threshold, then the power allocation termination condition is determined to be met; the latest expected power of each energy storage unit before the time when the power allocation termination condition is met is taken as the expected output power, and the photovoltaic energy storage system is operated based on the expected output power of each energy storage unit.

[0017] By adopting the above technical solution, the power allocation termination condition is set by keeping the sum of the current energy storage unit operation flags unchanged or the difference power less than a preset threshold during the iteration process. This allows for dynamic and accurate determination of whether the power allocation has reached a stable and reasonable state, avoiding unnecessary continuous iterations and improving allocation efficiency. When the termination condition is met, the latest expected power of each energy storage unit before the termination time is taken as the expected output power. This ensures that the output power meets the actual operating requirements of the system and enables each energy storage unit to operate at a reasonable power, thus guaranteeing the stable and efficient operation of the photovoltaic-energy storage system.

[0018] In a preferred embodiment, this application can be further configured to: obtain the desired power range of each energy storage unit in the photovoltaic-energy storage system, including: For any energy storage unit in the photovoltaic energy storage system, determine the current SOC of the energy storage unit; Substitute the current SOC into the segmented power derating function to determine the upper and lower limits of the expected power corresponding to the current SOC in the segmented power derating function. The upper and lower limits of the expected power corresponding to the current SOC constitute the expected power range of the energy storage unit. The segmented power derating function includes the upper limit and lower limit of the expected power corresponding to different SOC ranges.

[0019] By adopting the above technical solution, the current SOC of the energy storage unit is determined; by substituting the current SOC into the piecewise power derating function, the corresponding upper and lower limits of the expected power can be scientifically and reasonably determined according to the different ranges of SOC, thus forming the expected power range; this not only takes into account the actual remaining power of the energy storage unit, but also uses the piecewise function to carefully define the power boundary, avoiding damage to the energy storage unit due to the power exceeding the reasonable range.

[0020] Secondly, this application provides a photovoltaic energy storage system, which adopts the following technical solution: A photovoltaic-storage system includes: a photovoltaic unit, an energy storage unit, a load unit, an AC grid, and a controller; The photovoltaic unit is used to convert solar energy into electrical energy; The energy storage unit is used to store the surplus electrical energy of the photovoltaic unit and the off-peak electrical energy of the AC grid, and to discharge it. The AC power grid is used to supply power when the photovoltaic unit and the energy storage unit are insufficient, and to absorb excess power when the photovoltaic unit and the energy storage unit have excess power. The load unit is used to consume electrical energy; The controller is used to coordinate the operation of the energy storage unit, the load unit, the AC grid and the photovoltaic unit, and to execute the energy storage SOC balancing method applied to the distributed photovoltaic-storage system as described in any of the first aspects.

[0021] In a preferred embodiment, this application can be further configured as: a controller comprising: One or more processors; Memory; At least one application, wherein the at least one application is stored in memory and configured to be executed by at least one processor, the at least one application being configured to: execute the energy storage SOC equalization method applied to a distributed photovoltaic energy storage system as described in any of the first aspects.

[0022] Thirdly, this application provides a computer-readable storage medium, which adopts the following technical solution: A computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the energy storage SOC equalization method applied to a distributed photovoltaic energy storage system as described in any of the first aspects.

[0023] Fourthly, this application provides a computer program product, which adopts the following technical solution: A computer program product includes a computer program that, when executed by a processor, implements the energy storage SOC equalization method for a distributed photovoltaic energy storage system as described in any of the first aspects.

[0024] In summary, this application includes the following beneficial technical effects: This application obtains key parameters of the photovoltaic-storage system and defines power constraints to provide a foundation and standard for subsequent operations, ensuring reasonable and legal power allocation. Based on the obtained parameters, it determines the working energy storage units, accurately selecting units that can participate in power allocation, avoiding ineffective participation, and improving system operating efficiency. It allocates the overall power to the working energy storage units to obtain the initial expected power, providing an initial value for power balance adjustment. By iteratively executing the power derating and redistribution steps, it continuously adjusts the power of dated and non-dated energy storage units, gradually achieving reasonable power redistribution, ultimately ensuring that the expected output power of each energy storage unit meets system requirements, achieving SOC balance of the energy storage units, and improving the stability and reliability of the photovoltaic-storage system. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the architecture of a photovoltaic storage system provided in an embodiment of this application; Figure 2 This is a control strategy diagram of a photovoltaic energy storage system provided in this embodiment; Figure 3 This is a flowchart illustrating a method for balancing the energy storage SOC in a distributed photovoltaic-storage system, as provided in an embodiment of this application. Figure 4 This is a flowchart illustrating the equalization algorithm provided in an embodiment of this application; Figure 5 This is a schematic diagram of the structure of a controller provided in an embodiment of this application. Detailed Implementation

[0026] The following is in conjunction with the appendix Figure 1 To be continued Figure 5 This application will be described in further detail.

[0027] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0030] It should be noted that, in the optional embodiments of this application, the data related to object information, when applied to specific products or technologies, requires the permission or consent of the object. Furthermore, the collection, use, and processing of this data must comply with the relevant laws, regulations, and standards of the relevant countries and regions. In other words, if the embodiments of this application involve data related to an object, it must be obtained with the object's authorization and consent, the authorization and consent of relevant departments, and in accordance with the relevant laws, regulations, and standards of the country and region. If the embodiments involve personal information, the acquisition of all personal information requires the individual's consent. If sensitive information is involved, the separate consent of the information subject is required. The embodiments also need to be implemented with the object's authorization and consent.

[0031] This application provides an embodiment of a photovoltaic energy storage system, such as... Figure 1 As shown, the system includes: photovoltaic units (the system includes n photovoltaic units), energy storage units (the system includes m PCS as energy storage units), load units (such as the load in 1), AC grid and controller.

[0032] Specifically, photovoltaic (PV) units are used to convert solar energy into electrical energy. Energy storage units are used to store excess electrical energy from the PV units and off-peak electricity from the AC grid, and to discharge this energy. The AC grid is used to supply power when the PV units and energy storage units are insufficient, and to absorb excess power when the PV units and energy storage units have excess power. Load units are used to consume electrical energy. A controller is used to coordinate the operation of the energy storage units, load units, AC grid, and PV units, and to execute the energy storage SOC equalization method for distributed PV-storage systems provided in this application embodiment.

[0033] See Figure 2 This diagram illustrates a control strategy for a photovoltaic-storage system provided in this embodiment. The PVI (PVinverter) employs Maximum Power Point Tracking (MPPT) technology, and the PCS uses a VSG (Virtual Synchronous Generator) control system with grid-support capabilities. Due to the intermittent, fluctuating, and random nature of photovoltaics, the overall photovoltaic output power P... pv (t) represents a time-varying state; the load is affected by the electricity demand of users, and the load consumes power P. load (t) is usually a time-varying state.

[0034] This application provides a method for SOC equalization of energy storage in distributed photovoltaic-energy storage systems, applicable to distributed photovoltaic-energy storage systems with multiple energy storage units operating in parallel with the grid. The core algorithm is based on weighted dynamic power allocation. Figure 3As shown, the method provided in this embodiment is executed by a controller, which can be a server or a terminal device. The server can be an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services. The terminal device can be a smartphone, tablet, laptop, desktop computer, etc., but is not limited to these. The terminal device and the server can be directly or indirectly connected via wired or wireless communication. This embodiment does not impose any limitations on this connection. The method includes steps S301-S304, wherein: S301. Obtain the overall expected energy storage power of the photovoltaic energy storage system, the SOC and expected power range of each energy storage unit, and define the power constraints.

[0035] Specifically, the system receives the overall expected energy storage power of the photovoltaic-energy storage system from the upper-level controller, and the controller collects the State of Charge (SOC) of each energy storage unit in real time. For any given energy storage unit, the expected power range of that unit is dynamically updated based on its SOC.

[0036] The power constraints include upper and lower limit constraints for energy storage units and power conservation constraints. The upper and lower limit constraints for energy storage units state that the desired power of each energy storage unit in the photovoltaic-energy storage system does not exceed its corresponding desired power range. The power conservation constraint states that the sum of the desired power of all energy storage units in the photovoltaic-energy storage system equals the overall desired energy storage power, i.e., the overall desired energy storage power. The sum of the lower bounds of the expected power of all energy storage units in a photovoltaic-energy storage system Sum of the expected power limit Within the scope of what is constituted.

[0037] S302. Based on the overall expected power of energy storage, the SOC and expected power range of each energy storage unit, determine the working energy storage unit from each energy storage unit.

[0038] Specifically, based on the SOC of each energy storage unit, the maximum and minimum SOC are determined, and the difference between the maximum and minimum SOC is calculated as the maximum SOC difference ΔSOC. bal K serves as the start / stop flag for the load balancing algorithm. bal (1) is the start / stop flag of the equilibrium algorithm after the change at the current time, and is the flag of the previous time, i.e., K. bal (0) The start / stop flag of the equilibrium algorithm when ΔSOC is in the range of the equilibrium start / stop function and does not change.

[0039] The balanced start-stop piecewise function is: when ΔSOC is in [0, a), K bal(1) = 0, the balancing algorithm is not started. If the balancing algorithm was in the started state at the previous moment, the balancing algorithm stops at the current moment. When ΔSOC is in [a, b], K bal (1) = K bal (0), the start / stop state of the balancing algorithm remains unchanged. If the balancing algorithm was in the started state at the previous moment, it continues to be in the started state at the current moment. If the balancing algorithm was in the stopped state at the previous moment, it continues to be in the stopped state at the current moment. When ΔSOC is in (b, 1], K bal (1) = 1, regardless of the state of the balancing algorithm at the previous moment, it remains in the started state at the current moment. Here, a < b, a is the balancing stop threshold, and b is the balancing start threshold. Optionally, a = 2% and b = 4%.

[0040] When ΔSOC exceeds the balancing start threshold, a list of energy storage units is generated. The controller identifies the charge / discharge state of the system energy storage of the photovoltaic and energy storage system, and determines the working energy storage units that can meet the overall energy storage expected power from each energy storage unit based on the charge / discharge state of the system energy storage.

[0041] S303. Allocate the overall energy storage expected power to the working energy storage units to obtain the initial expected power of each working energy storage unit.

[0042] In a possible case, the charge / discharge state of the system energy storage is the discharge state. Calculate the product of the SOC of each energy storage unit and the upper limit of the expected power as the first value, and calculate the sum of the first values of the working energy storage units as the second value. For each working energy storage unit, calculate the ratio of the first value of this energy storage unit to the second value as the first ratio, and calculate the product of the first ratio and the overall energy storage expected power as the initial expected power of this energy storage unit; In another possible case, the charge / discharge state of the system energy storage is the charge state. Calculate the product of the depth of discharge of each energy storage unit and the lower limit of the expected power as the third value, and calculate the sum of the third values of the working energy storage units as the fourth value. For each working energy storage unit, calculate the ratio of the third value of this energy storage unit to the fourth value as the second ratio, and calculate the product of the second ratio and the overall energy storage expected power as the initial expected power of this energy storage unit.

[0043] S304. Iteratively execute the power derating and redistribution step until the power distribution termination condition is met to obtain the expected output power of each energy storage unit. Take the working energy storage units as the current energy storage units. The power derating and redistribution step includes: dividing the current energy storage units into derated energy storage units and non-derated energy storage units; adjusting the current expected power of the derated energy storage units based on the current expected power and the expected power range of the derated energy storage units to complete power derating, and determining the differential power based on the power constraint conditions; allocating the differential power to the non-derated energy storage units; and updating the non-derated energy storage units as the current energy storage units.

[0044] Specifically, for any energy storage unit, its operating flag K bat Indicates whether the system is operating normally. The initial value of the operation flag for each energy storage unit is 1, K. bat =1 indicates that the energy storage unit is operating normally (no power derating has been performed). During any iteration, if the energy storage unit experiences power derating, its corresponding operation flag is updated to K. bat =0. K bat (0) indicates the operating status of the energy storage unit at the previous moment (before the current iteration), K bat (1) The result of updating the operation flag of the derated energy storage unit after the power derating is completed in the current iteration process.

[0045] The power allocation termination conditions include: the sum of the operating flags of the current energy storage units does not change (i.e., no new derating energy storage units appear, and the expected power of each energy storage unit is within the corresponding expected power range), or the difference in power is less than a preset difference in power threshold, which determines that the power allocation termination conditions are met. The preset difference in power threshold can be freely set, such as 0.1kW.

[0046] See Figure 4 The diagram illustrates the flow chart of the power equalization algorithm proposed in this application. This embodiment obtains key parameters of the photovoltaic-storage system and defines power constraints, providing a foundation and standard for subsequent operations and ensuring reasonable and legal power allocation. Based on the obtained parameters, it determines the working energy storage units, accurately selecting units that can participate in power allocation, avoiding ineffective participation, and improving system operating efficiency. It allocates the overall power to the working energy storage units to obtain the initial expected power, providing an initial value for power equalization adjustment. Through iterative execution of the power derating and redistribution steps, it continuously adjusts the power of dated and non-dated energy storage units, gradually achieving reasonable power redistribution, ultimately ensuring that the expected output power of each energy storage unit meets system requirements, achieving SOC equalization of the energy storage units, and improving the stability and reliability of the photovoltaic-storage system.

[0047] One possible implementation of this application embodiment, obtaining the expected power range of each energy storage unit in a photovoltaic energy storage system, includes: For any energy storage unit in a photovoltaic-energy storage system, determine the current SOC of the energy storage unit; Substitute the current SOC into the segmented power derating function to determine the upper and lower limits of the expected power corresponding to the current SOC in the segmented power derating function. The upper and lower limits of the expected power corresponding to the current SOC constitute the expected power range of the energy storage unit. The piecewise power derating function includes the upper and lower limits of the expected power corresponding to different SOC ranges.

[0048] In this embodiment, multiple SOC ranges are pre-defined based on experiments or experience, with each range corresponding to an upper and lower limit of expected power. The correspondence between the SOC range and the upper and lower limits of expected power constitutes a piecewise power derating function. During the operation of the photovoltaic-storage system, the range of the current SOC is dynamically determined, and the corresponding upper and lower limits of expected power are selected as the expected power range of the energy storage unit at the current moment.

[0049] j represents any energy storage unit, j = 1, ..., m, SOC j (t) represents the current SOC of the energy storage unit. This indicates the upper limit of the expected power range of the energy storage unit. P represents the lower limit of the expected power range of the energy storage unit. Nj This indicates the rated output power of the energy storage unit.

[0050] The piecewise power derating function is expressed as: SOC j (t) = 100%, 95% ≤ SOC j (t) < 100%, 85% ≤ SOC j (t) < 95%, 15% ≤ SOC j (t) < 85%, 5% ≤ SOC j (t) < 15%, 0% < SOC j (t) < 5%, SOC j (t) = 0%, This embodiment determines the current SOC of the energy storage unit and substitutes the current SOC into the piecewise power derating function. Based on the different ranges of SOC, it can scientifically and reasonably determine the corresponding upper and lower limits of the expected power, thus forming the expected power range. It takes into account the actual remaining power of the energy storage unit and can also define the power boundary in detail through the piecewise function, so as to avoid damage to the energy storage unit due to the power exceeding the reasonable range.

[0051] One possible implementation of this application embodiment includes power constraint conditions comprising upper and lower limit constraints for energy storage units and power conservation constraints; defining power constraint conditions includes: The upper and lower limit constraints of the energy storage unit are defined as follows: the expected power of each energy storage unit in the photovoltaic-energy storage system shall not exceed the corresponding expected power range. The power conservation constraint is defined as follows: the sum of the expected power of all energy storage units in the photovoltaic-energy storage system is equal to the overall expected power of energy storage.

[0052] In this embodiment, the upper and lower limit constraints of the energy storage unit are defined as: the expected power of any energy storage unit j in the photovoltaic-energy storage system. Not exceeding the corresponding expected power range (the upper limit of the expected power range is...) The lower limit of the expected power range is ).

[0053] According to the principle of power conservation, we can obtain: Among them, P pvi P represents the output power of the i-th PVI, and n is the number of PVIs; batj P represents the output power of the j-th energy storage inverter, where m is the number of PCS. pv The overall PVI output power of the system; P bat The overall PCS output power; P load Power consumed by the load (power consumed by the load unit); P g Power supplied to the AC power grid.

[0054] Due to the photovoltaic output power P pv and load power consumption P load Random variable, controlled by adjusting the overall PCS output power P bat This enables energy flow control of distributed photovoltaic-storage systems. The controller collects relevant information from photovoltaics, loads, energy storage, and the power grid to generate the overall expected power of the energy storage system.

[0055] Define the power conservation constraint: the sum of the desired power of all energy storage units in the photovoltaic-energy storage system (the desired power of any energy storage unit j is...). () equals the total expected power of energy storage The expression is: in, This indicates that the energy storage unit is discharging. This indicates that the energy storage unit is charging.

[0056] It can be further concluded that,

[0057] in, This represents the lower limit of the expected power of the j-th energy storage unit. This represents the expected upper limit of the power of the j-th energy storage unit. This represents the lower limit of the overall expected energy storage capacity. This indicates the upper limit of the expected overall energy storage power.

[0058] This embodiment defines upper and lower limit constraints for energy storage units to ensure that the expected power of each energy storage unit is within a reasonable range, preventing damage to equipment due to excessive power or ineffective energy storage due to insufficient power, thus ensuring the safety and stability of the energy storage unit's operation. Furthermore, it defines power conservation constraints to ensure that the sum of the expected power of all energy storage units is equal to the overall expected power of the energy storage system, guaranteeing the overall power balance of the photovoltaic-energy storage system. This allows the system to accurately allocate and regulate power according to demand, improving the reliability and coordination of system operation.

[0059] One possible implementation of this application embodiment involves determining the working energy storage unit from among the various energy storage units based on the overall expected energy storage power, the SOC of each energy storage unit, and the expected power range, including: Calculate the maximum SOC difference based on the SOC of each energy storage unit; The maximum SOC difference is substituted into the equalization start-stop segmentation function. When the maximum SOC difference exceeds the equalization start threshold, the equalization algorithm is started. Arrange the energy storage units in descending order of their corresponding SOC to obtain a list of energy storage units; Based on the overall expected power of energy storage and the expected power range of each energy storage unit, the charging and discharging state of the system energy storage is identified. Based on the system's energy storage charge and discharge status, the working energy storage unit that can meet the overall energy storage expected power is determined from each energy storage unit.

[0060] In this embodiment, when At that time, the system's energy storage charging and discharging state is in the discharging state, and the k-th energy storage unit in the energy storage unit list E satisfies: Where E(d) represents the d-th energy storage unit in the energy storage unit list.

[0061] So, the device start / stop flag K of the energy storage unit word It can be represented as: when At that time, the system's energy storage charging and discharging state is the charging state, and the k-th energy storage unit in the energy storage unit list E satisfies: Where E(d) represents the d-th energy storage unit in the energy storage unit list.

[0062] So, the device start / stop flag K of the energy storage unit word It can be represented as: Among them, K wordE(d)=1 indicates that the energy storage device is in operation, K wordE(d) =0 indicates that the energy storage device is not operating.

[0063] when At this time, the photovoltaic-energy storage system neither charges nor discharges, all energy storage units are not operating, and the equipment start / stop flags are all 0. At that time, the photovoltaic-energy storage system is at maximum discharge, and the start / stop flags of all energy storage units are set to 1, with all units operating at the desired power limit. At that time, the photovoltaic-storage system is at its maximum charging state, and the start / stop flags of all energy storage units are all set to 1 and all are operating at the lower limit of the desired power.

[0064] Therefore, based on the determined equipment start / stop flags, it is possible to identify the operating energy storage unit.

[0065] This embodiment calculates the maximum SOC difference of each energy storage unit to measure the degree of SOC difference and provides a basis for whether to start balancing. Substituting this value into the balancing start-stop piecewise function, the balancing algorithm is activated when the start threshold is exceeded, which can avoid unnecessary balancing operations and save system resources. The energy storage units are arranged into a list according to SOC from largest to smallest. The charging and discharging state of the system's energy storage is identified. Combining the overall expected power of energy storage and the expected power range of each unit, the working energy storage units that can meet the power requirements and fit the current charging and discharging state can be accurately selected.

[0066] One possible implementation of this application embodiment is that the desired power range includes an upper limit and a lower limit of desired power, and any working energy storage unit is taken as the target energy storage unit; the overall desired energy storage power is allocated to the working energy storage units to obtain the initial desired power of each working energy storage unit, including: Obtain the charging and discharging status of the system's energy storage; When the system energy storage is in the discharge state, the product of the SOC of each energy storage unit and the upper limit of the expected power is calculated as the first value, and the sum of the first values ​​of the working energy storage units is calculated as the second value; the ratio of the first value and the second value of the target energy storage unit is calculated as the first ratio, and the product of the first ratio and the overall expected power of energy storage is calculated as the initial expected power of the target energy storage unit. When the system's energy storage is in the charging state, the product of the discharge depth and the lower limit of the expected power of each energy storage unit is calculated as the third value, and the sum of the third values ​​of the working energy storage units is calculated as the fourth value; the ratio of the third value and the fourth value of the target energy storage unit is calculated as the second ratio, and the product of the second ratio and the overall expected power of energy storage is calculated as the initial expected power of the target energy storage unit.

[0067] In this embodiment, the overall expected power of energy storage is determined based on the charge and discharge potential of the energy storage unit. The energy storage unit's State of Charge (SOC) is allocated accordingly. A higher SOC indicates a greater discharge potential, while a lower SOC indicates a greater charging potential.

[0068] When the system's energy storage is in a discharge state, each energy storage unit is also in a discharge state. For any energy storage unit j, j = 1, ..., m, Its SOC is represented as SOC j Its initial expected power The expression is: When the system's energy storage is in a discharge state, each energy storage unit is also in a discharge state. For any energy storage unit j, Its SOC is represented as SOC j Its initial expected power The expression is: This embodiment obtains the charging and discharging status of the system's energy storage. In the discharging state, power is allocated according to the ratio of the product of the energy storage unit's SOC and the expected power limit, allowing units with higher SOC and larger power limits to undertake more discharging tasks and make full use of their current energy storage capacity. In the charging state, power is allocated according to the ratio of the product of the depth of discharge and the expected power limit, allowing units with a large depth of discharge and a reasonable power limit to charge first, thus balancing the status of each energy storage unit.

[0069] One possible implementation of this application embodiment is to divide the current energy storage unit into drated energy storage units and non-drated energy storage units, including: comparing the current expected power of each energy storage unit in the current energy storage unit with the corresponding expected power range, determining the energy storage unit whose current expected power exceeds the corresponding expected power range as a drated energy storage unit, and determining the energy storage unit whose current expected power does not exceed the corresponding expected power range as a non-drated energy storage unit; Adjust the operating indicators of the derated energy storage unit.

[0070] In this embodiment, for any energy storage unit, its operation flag K bat Indicates whether the system is operating normally. The initial value of the operation flag for each energy storage unit is 1, K. bat =1 indicates that the energy storage unit is operating normally (no power derating has been performed). During any iteration, after identifying the drated energy storage unit, its power needs to be adjusted, and its operating flags also need to be adjusted. The adjustment method is as follows: If the current iteration is the first iteration after allocating the overall expected power, then the current expected power of the energy storage unit is the initial expected power of each working energy storage unit determined during the allocation of the overall expected power; if the current iteration is not the first iteration, then the current expected power of the energy storage unit is the latest expected power of each energy storage unit determined after the previous iteration was completed.

[0071] This represents the current expected power of any given energy storage unit. This represents the latest expected power after the current iteration process completes the power derating. K batj (1) indicates the result after adjusting the operating flags of the derating energy storage unit after the current iteration process is completed, K batj (1) = 1 indicates that the energy storage unit is operating normally in the current iteration (without power derating), K batj (1) = 0 indicates that the energy storage unit performs power derating in the current iteration.

[0072] Energy storage units whose current expected power does not exceed the corresponding expected power range are considered as non-dated energy storage units, and their K... batj (1) = 1, corresponding to the current expected power not being adjusted, i.e.

[0073] Energy storage units whose current expected power exceeds the corresponding expected power range are identified as derating energy storage units. If the current expected power... Not higher than the lower limit of expected power Then the current expected power of the derating energy storage unit will be adjusted to the lower limit of the expected power. K batj (1) = 0.

[0074] If the current expected power of the derated energy storage unit Not lower than the upper limit of expected power Then the current expected power of the derated energy storage unit will be adjusted to the upper limit of the expected power. K batj (1) = 0.

[0075] This embodiment accurately identifies energy storage units with abnormal power by comparing their current expected power with the expected power range. These units are classified as drated energy storage units, allowing for timely control of units exceeding power limits and preventing damage due to unreasonable power operation. Units with normal power are classified as non-drated energy storage units, ensuring the continuous and stable operation of normal units. Furthermore, adjusting the operation flags of drated energy storage units clearly marks these abnormal units, facilitating subsequent targeted adjustments and handling of their power.

[0076] One possible implementation of this application embodiment involves adjusting the current expected power of the derating energy storage unit based on its current expected power and expected power range to achieve power derating, including: For any dated energy storage unit, compare the current expected power of the dated energy storage unit with the expected power range of the dated energy storage unit; If the current expected power of the derated energy storage unit is not higher than the lower limit of the expected power, then the current expected power of the derated energy storage unit will be adjusted to the lower limit of the expected power. If the current expected power of the derated energy storage unit is not lower than the upper limit of the expected power, then the current expected power of the derated energy storage unit will be adjusted to the upper limit of the expected power.

[0077] This embodiment compares the current expected power of the derating energy storage unit with its expected power range to accurately locate the current power within a reasonable range. If the current expected power is not higher than the lower limit of the expected power, it is adjusted to the lower limit of the expected power to avoid the power being too low and affecting the normal operation of the energy storage unit, thus ensuring its basic operating capability. If the current expected power is not lower than the upper limit of the expected power, it is adjusted to the upper limit of the expected power to prevent the power from being too high and exceeding the energy storage unit's tolerance range, thus ensuring its safe and stable operation. Through such adjustments, the power is effectively controlled within a reasonable range, realizing the standardized operation of power derating.

[0078] One possible implementation of this application embodiment involves iteratively executing the power derating and redistribution step until the power allocation termination condition is met, to obtain the desired output power of each energy storage unit, including: In the power derating and redistribution step, if the sum of the operating flags of the current energy storage unit does not change during the current iteration, or if the differential power is less than the preset differential power threshold, then the power distribution termination condition is determined to be met. The latest expected power of each energy storage unit before the power allocation termination condition is met is taken as the expected output power, and the photovoltaic-energy storage system is operated based on the expected output power of each energy storage unit.

[0079] In this embodiment, the sum M of the operating flags of each energy storage unit is represented as: During any iteration, if M changes, it indicates that there is a power derating of the energy storage unit during this iteration, and the difference in power needs to be redistributed. One of the termination conditions for power allocation is: Where M(1) represents the sum of the energy storage unit operation flags after adjustment in the current iteration process, and M(0) represents the sum of the energy storage unit operation flags after adjustment in the previous iteration process.

[0080] Calculate the differential power during the current iteration:

[0081] Referring to the process of allocating the overall expected power of energy storage, the difference in power is redistributed to the underated energy storage units.

[0082] in, This indicates the result of allocating the power difference to the un-dated energy storage unit.

[0083] In this embodiment, the sum of the current energy storage unit operation flags remains unchanged or the difference in power is less than a preset threshold as the power allocation termination condition during the iteration process. This can dynamically and accurately determine whether the power allocation has reached a stable and reasonable state, avoid unnecessary continuous iteration, and improve allocation efficiency. When the termination condition is met, the latest expected power of each energy storage unit before the termination time is taken as the expected output power. This ensures that the output power meets the actual operating requirements of the system and enables each energy storage unit to work at a reasonable power, thus ensuring the stable and efficient operation of the photovoltaic energy storage system.

[0084] This application provides a controller, such as... Figure 5 As shown, Figure 5 The controller 500 shown includes a processor 501 and a memory 503. The processor 501 and the memory 503 are connected, for example, via a bus 502. Optionally, the controller 500 may also include a transceiver 504. It should be noted that in practical applications, the transceiver 504 is not limited to one type, and the structure of this controller 500 does not constitute a limitation on the embodiments of this application.

[0085] Processor 501 may be a CPU (Central Processing Unit), a general-purpose processor, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. Processor 501 may also be a combination that implements computational functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc.

[0086] Bus 502 may include a pathway for transmitting information between the aforementioned components. Bus 502 may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. Bus 502 can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 5 The symbol is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0087] The memory 503 may be a ROM (Read Only Memory) or other type of static storage device capable of storing static information and instructions, RAM (Random Access Memory) or other type of dynamic storage device capable of storing information and instructions, or an EEPROM (Electrically Erasable Programmable Read Only Memory), CD-ROM (Compact Disc Read Only Memory) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto.

[0088] The memory 503 is used to store the application code that executes the scheme of this application, and its execution is controlled by the processor 501. The processor 501 is used to execute the application code stored in the memory 503 to implement the content shown in the aforementioned embodiment of the energy storage SOC balancing method applied to a distributed photovoltaic energy storage system.

[0089] Figure 5 The controller shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of this application.

[0090] This application provides a computer-readable storage medium storing a computer program that, when run on a computer, enables the computer to execute the content shown in the aforementioned embodiment of the energy storage SOC equalization method applied to a distributed photovoltaic energy storage system.

[0091] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0092] This application provides a computer program product, including a computer program that, when executed by a processor, implements the content shown in the aforementioned embodiment of the energy storage SOC balancing method applied to a distributed photovoltaic energy storage system.

[0093] The above are only some embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for equalizing the state of energy storage (SOC) in a distributed photovoltaic-storage system, characterized in that, include: Obtain the overall expected energy storage power of the photovoltaic-energy storage system, the SOC and expected power range of each energy storage unit, and define the power constraints. Based on the overall expected energy storage power, the SOC and expected power range of each energy storage unit, the working energy storage unit is determined from the various energy storage units; The overall desired energy storage power is allocated to the working energy storage units to obtain the initial desired power of each working energy storage unit; The power derating and redistribution steps are executed iteratively until the power distribution termination condition is met, and the expected output power of each energy storage unit is obtained. The working energy storage unit is used as the current energy storage unit, and the power derating redistribution step includes: dividing the current energy storage unit into drated energy storage units and non-drated energy storage units; The current expected power of the derated energy storage unit is adjusted based on the current expected power and expected power range of the derated energy storage unit to complete the power derated, and the difference power is determined based on the power constraint condition; the difference power is allocated to the non-derated energy storage unit; and the non-derated energy storage unit is updated as the current energy storage unit.

2. The energy storage SOC equalization method applied to distributed photovoltaic-storage systems according to claim 1, characterized in that, The step of determining the working energy storage unit from the various energy storage units based on the overall expected power of energy storage, the SOC of each energy storage unit, and the expected power range of each energy storage unit includes: Calculate the maximum SOC difference based on the SOC of each energy storage unit; Substitute the maximum SOC difference into the equalization start-stop segmentation function. When the maximum SOC difference exceeds the equalization start threshold, the equalization algorithm is started. Arrange the energy storage units in descending order of their corresponding SOC to obtain an energy storage unit list; Based on the overall expected power of energy storage and the expected power range of each energy storage unit, the charging and discharging state of the system energy storage is identified. Based on the system's energy storage charging and discharging state, the working energy storage unit that can meet the overall expected energy storage power is determined from among the various energy storage units.

3. The energy storage SOC equalization method applied to distributed photovoltaic-storage systems according to claim 1, characterized in that, The desired power range includes an upper limit and a lower limit, with any working energy storage unit as the target energy storage unit; the overall desired energy storage power is allocated to the working energy storage units to obtain the initial desired power for each working energy storage unit, including: Obtain the charging and discharging status of the system's energy storage; When the system energy storage is in the discharge state, the product of the SOC of each energy storage unit and the upper limit of the expected power is calculated as a first value, and the sum of the first values ​​of the working energy storage units is calculated as a second value; the ratio of the first value and the second value of the target energy storage unit is calculated as a first ratio, and the product of the first ratio and the overall expected power of energy storage is calculated as the initial expected power of the target energy storage unit. When the system's energy storage charging and discharging state is in the charging state, the product of the discharge depth and the lower limit of the expected power of each energy storage unit is calculated as a third value, and the sum of the third values ​​of the working energy storage units is calculated as a fourth value; the ratio of the third value and the fourth value of the target energy storage unit is calculated as a second ratio, and the product of the second ratio and the overall expected power of energy storage is calculated as the initial expected power of the target energy storage unit.

4. The energy storage SOC equalization method applied to distributed photovoltaic-storage systems according to claim 1, characterized in that, The step of adjusting the current expected power of the derated energy storage unit based on its current expected power and expected power range to complete power dereasing includes: For any derating energy storage unit, the current expected power of the derating energy storage unit is compared with the expected power range of the derating energy storage unit; If the current expected power of the derating energy storage unit is not higher than the lower limit of the expected power, then the current expected power of the derating energy storage unit is adjusted to the lower limit of the expected power. If the current expected power of the derating energy storage unit is not lower than the upper limit of the expected power, then the current expected power of the derating energy storage unit will be adjusted to the upper limit of the expected power.

5. The energy storage SOC equalization method applied to distributed photovoltaic-storage systems according to claim 1, characterized in that, The power constraints include upper and lower limit constraints for the energy storage unit and power conservation constraints; the definition of the power constraints includes: The upper and lower limit constraints of the energy storage unit are defined as follows: the expected power of each energy storage unit in the photovoltaic energy storage system does not exceed the corresponding expected power range. The power conservation constraint is defined as follows: the sum of the expected power of all energy storage units in the photovoltaic-energy storage system is equal to the overall expected energy storage power.

6. The energy storage SOC equalization method applied to a distributed photovoltaic-storage system according to claim 1, characterized in that, The step of dividing the current energy storage unit into derated energy storage units and non-derated energy storage units includes: The current expected power of each energy storage unit in the current energy storage unit is compared with the corresponding expected power range. The energy storage unit whose current expected power exceeds the corresponding expected power range is identified as a drated energy storage unit, and the energy storage unit whose current expected power does not exceed the corresponding expected power range is identified as a non-drated energy storage unit. Adjust the operating flags of the derated energy storage unit.

7. The energy storage SOC equalization method applied to distributed photovoltaic-storage systems according to claim 1, characterized in that, The iterative execution of the power derating and redistribution step continues until the power allocation termination condition is met, obtaining the expected output power of each energy storage unit, including: In the power derating and redistribution step, if the sum of the operating flags of the current energy storage unit does not change during the current iteration, or if the differential power is less than the preset differential power threshold, then the power distribution termination condition is determined to be met. The latest expected power of each energy storage unit before the power allocation termination condition is met is taken as the expected output power, and the photovoltaic energy storage system is operated based on the expected output power of each energy storage unit.

8. The energy storage SOC equalization method applied to a distributed photovoltaic-storage system according to claim 1, characterized in that, Obtain the expected power range of each energy storage unit in the photovoltaic-energy storage system, including: For any energy storage unit in the photovoltaic energy storage system, determine the current SOC of the energy storage unit; Substitute the current SOC into the segmented power derating function to determine the upper and lower limits of the expected power corresponding to the current SOC in the segmented power derating function. The upper and lower limits of the expected power corresponding to the current SOC constitute the expected power range of the energy storage unit. The segmented power derating function includes the upper limit and lower limit of the expected power corresponding to different SOC ranges.

9. A photovoltaic energy storage system, characterized in that, include: Photovoltaic units, energy storage units, load units, AC power grid, and controllers; The photovoltaic unit is used to convert solar energy into electrical energy; The energy storage unit is used to store the surplus electrical energy of the photovoltaic unit and the off-peak electrical energy of the AC grid, and to discharge it. The AC power grid is used to supply power when the photovoltaic unit and the energy storage unit are insufficient, and to absorb excess power when the photovoltaic unit and the energy storage unit have excess power. The load unit is used to consume electrical energy; The controller is used to coordinate the operation of the energy storage unit, the load unit, the AC grid and the photovoltaic unit, and to execute the energy storage SOC balancing method applied to a distributed photovoltaic-storage system as described in any one of claims 1-8.

10. The photovoltaic energy storage system according to claim 9, characterized in that, The controller includes: At least one processor; Memory; At least one application, wherein the at least one application is stored in memory and configured to be executed by at least one processor, said at least one application being configured to: perform the energy storage SOC equalization method for a distributed photovoltaic energy storage system as described in any one of claims 1-8.

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