Energy storage system and control method thereof

Abstract

The invention provides an energy storage system and a control method thereof, and belongs to the technical field of energy storage. A power converter in the energy storage system is used for charging and discharging a battery cell in a battery pack. The actual capacity of a battery cell in the battery pack is the first capacity, and a battery management module in the battery pack can control the charging and discharging capacity (namely the claimed capacity) of the battery cell to be smaller than the first capacity in the process that the power converter charges and discharges the battery cell. As the actual capacity of the battery cell has certain redundancy compared with the charge-discharge capacity of the battery cell, the actual charge-discharge depth of the battery cell can be effectively reduced, and the actual charge-discharge depth of the battery cell is prevented from reaching 100%. And the deeper the charge-discharge depth of the battery cell is, the faster the performance degradation is, so that the scheme provided by the embodiment of the invention can effectively reduce the performance degradation rate of the battery cell and prolong the service life of the battery pack.

Description

Technical Field

[0001] This application relates to the technical field of energy storage, and particularly to an energy storage system and its control method. Background Art

[0002] An energy storage system usually includes multiple battery packs. As the service life of the battery pack (pack) increases, the performance of the battery pack will gradually decline. For example, the actual available capacity of the battery pack will gradually decrease. Moreover, during the use of the battery pack, if the charge-discharge depth is relatively deep, the rate of its performance decay will be accelerated. Summary of the Invention

[0003] This application provides an energy storage system and its control method, which can solve the technical problem that the charge-discharge depth of the battery pack in the energy storage system is relatively deep, resulting in an excessively fast performance decay rate.

[0004] In a first aspect, an energy storage system is provided. The energy storage system includes: a battery pack and a power converter. The battery pack includes: battery cells and a battery management module. Among them, the capacity of the battery cells is a first capacity, and the first capacity refers to the actual capacity of the battery cells in the battery pack. One end of the power converter is connected to the battery pack, and the other end of the power converter is used to connect to the power grid and the load. The power converter is used to charge the battery cells after power conversion of the power output by the power grid, and is used to supply power to the load after power conversion of the power output by the battery cells. The battery management module is used to control the charging capacity of the battery cells to be a second capacity during the process of the power converter charging the battery cells, and is used to control the discharging capacity of the battery cells to be a second capacity during the process of the power converter discharging the battery cells. The second capacity is less than the first capacity.

[0005] It can be understood that the above charging capacity refers to the actual charge amount that the battery cells are allowed to receive during charging; the discharging capacity refers to the actual charge amount that the battery cells are allowed to release during discharging. Moreover, the second capacity is the declared capacity of the battery cells in the battery pack, also known as the nominal capacity, that is, the second capacity is the capacity marked on the battery pack.

[0006] In the solution provided by this application, since the actual capacity of the battery cells in the battery pack has a certain redundancy compared to its charge-discharge capacity (i.e., the declared capacity), the actual charge-discharge depth of the battery pack can be effectively reduced, and it is avoided that the actual charge-discharge depth of the battery pack reaches 100%. Also, since the deeper the charge-discharge depth of the battery pack, the faster the performance decay, the solution provided by this application can effectively reduce the performance decay rate of the battery pack, and thus extend the service life of the battery pack.

[0007] In addition, although the actual capacity of the battery cells in the battery pack is relatively large, the available charge and discharge capacity (i.e., the declared capacity) provided to customers is relatively small, so it can effectively avoid increasing the initial investment cost of customers. Moreover, since the actual capacity of the battery cells in the battery pack is greater than its declared capacity, even if the actual capacity of the battery pack decays over time, it can ensure that the charge and discharge capacity provided to customers can always meet its declared capacity for a long time. That is to say, for customers, the performance of the battery pack (such as the load time and load power) will not gradually decay compared to the initial performance, but can achieve zero decay in the long term to ensure a consistent long-term customer experience.

[0008] Optionally, the energy storage system further includes: a battery control unit (BCU), which is communicatively connected to the battery management module in the battery pack and is used to send instructions (also called unlocking instructions) to the battery management module. The battery management module is further configured to adjust both the charging capacity and the discharging capacity of the battery cells to a third capacity based on the received instructions. That is, to adjust the declared capacity (or nominal capacity) of the battery cells to the third capacity. Wherein, the third capacity is greater than the second capacity and less than or equal to the first capacity.

[0009] Wherein, the instruction can be sent by the server of the energy storage system to the BCU based on the customer's capacity expansion requirement. Since the actual capacity of the battery cells has a certain redundancy compared to the second capacity, when the customer's required power increases, the battery management module can unlock some or all of the redundant capacity to meet the customer's power consumption requirement. It can be seen from this that the energy storage system provided in this application has high usage flexibility and can flexibly meet the requirements of different application scenarios.

[0010] It can be understood that the battery management module in the battery pack can be a battery monitor unit (BMU). The BCU and the BMU in the battery pack can form a battery management system (BMS).

[0011] Optionally, the battery management module is further configured to control the charge and discharge range of the battery cells to be a target state of charge (SOC) range. Wherein, the difference between the lower limit of the target SOC range and 0 is less than the difference between the upper limit of the target SOC range and 1. That is, the target SOC range is a low SOC range. And the target SOC range is calculated based on the first capacity of the battery cells as the rated capacity.

[0012] It can be understood that, compared with the high SOC range, the performance degradation of the battery cells in the battery pack during long-term operation in the low SOC range is smaller. Therefore, by designing the above-mentioned target SOC range as the low SOC range, the performance degradation of the battery cells can be effectively alleviated, thereby extending the service life of the battery cells. Moreover, high-precision SOX parameter calibration can be achieved at the end of discharge (i.e., the low power range) in the low SOC range. In addition, compared with the high SOC range, the impact after the battery pack fails in the low SOC range is smaller. Among them, SOX can include SOC, state of health (SOH), state of power (SOP), state of energy (SOE), etc.

[0013] Optionally, the lower limit of the target SOC range is equal to 0, and the product of the upper limit of the target SOC range and the first capacity is equal to the second capacity. By setting the lower limit of the target SOC range to 0, the battery cells can operate in the lowest possible SOC range, thereby effectively slowing down their performance degradation.

[0014] Optionally, the battery management module is further configured to increase the upper limit of the charging rate of the battery cell during the charging process of the power converter when the battery cell meets the first condition. Wherein, the first condition includes at least one of the following conditions: the cumulative charge of the battery cell within the first time period is less than the first charge threshold; the cumulative discharge of the battery cell within the second time period is less than the second charge threshold; the number of times the discharge depth of the battery cell within the third time period is greater than the first depth threshold is less than the first number threshold; and, the number of times the charge depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

[0015] Based on the above first condition, it can be known that the battery management module can increase the upper limit of the charging rate of the battery cell when it detects that the throughput charge of the battery cell within a certain time period is low, or when the charge depth or discharge depth within a certain time period is shallow. It can be understood that when the operating conditions of the battery cell meet the above first condition, the performance degradation of the battery cell is relatively slow. Therefore, the battery management module can increase the upper limit of the charging rate of the battery cell to improve the performance of the battery cell. Thus, on the basis of ensuring the long-term stable performance of the battery cell, it can adapt to the excessive demands of customers in the short term and improve the customer experience.

[0016] Optionally, the battery management module is further configured to increase the upper limit of the discharge rate of the battery cell during the process of discharging the battery cell by the power converter when the battery cell meets the second condition. The second condition includes at least one of the following conditions: the cumulative charge amount of the battery cell within the first time period is less than the first charge threshold; the cumulative discharge amount of the battery cell within the second time period is less than the second charge threshold; the number of times that the depth of discharge of the battery cell within the third time period is greater than the first depth threshold is less than the first number threshold; and the number of times that the depth of charge of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

[0017] Based on the above second condition, it can be known that the battery management module can increase the upper limit of the discharge rate of the battery cell when it detects that the throughput power of the battery cell within a certain time period is low, or when the depth of charge or discharge of the battery cell within a certain time period is shallow. The discharge rate may be the same as or different from the above-mentioned charge rate. The second condition and the first condition may be the same or different, and the present application does not make any limitations thereto.

[0018] Optionally, the battery cells in the battery pack may be lithium iron phosphate battery cells.

[0019] Based on the characteristics of lithium iron phosphate battery cells, in the low SOC range and the high SOC range, the cell voltage of lithium iron phosphate battery cells changes significantly with the capacity. Based on this, it is necessary to accurately calibrate the SOX of the battery pack when the battery cell operates in the low SOC range or the high SOC range. Also, since the performance degradation of the battery cell during long-term operation in the high SOC range is relatively large and it is not friendly to the battery cell life, in the solution provided in the present application, for the battery cells using lithium iron phosphate battery cells, the above-mentioned target SOC range may be set as the low SOC range.

[0020] In a second aspect, a control method for an energy storage system is provided. The control method can be applied to the energy storage system provided in the first aspect above and can be executed by the battery management module in the battery pack. The energy storage system includes: a battery pack and a power converter. The battery pack includes battery cells and a battery management module, and the capacity of the battery cells is the first capacity. One end of the power converter is connected to the battery pack, and the other end of the power converter is used to connect to the power grid and the load. The power converter is configured to convert the power output by the power grid and then charge the battery cells, and is configured to convert the power output by the battery cells and then supply power to the load. The method includes: during the process of the power converter charging the battery cells, the battery management module controls the charging capacity of the battery cells to be the second capacity; during the process of the power converter discharging the battery cells, the battery management module controls the discharging capacity of the battery cells to be the second capacity. The second capacity is less than the first capacity.

[0021] Optionally, the energy storage system further includes a BCU, which is communicatively connected to the battery management module in the battery pack. The method further includes: the BCU sending an instruction to the battery management module, and the battery management module adjusting both the charging capacity and the discharging capacity of the battery cell to a third capacity based on the received instruction. Wherein, the third capacity is greater than the second capacity and less than or equal to the first capacity.

[0022] Optionally, the method further includes: the battery management module controlling the charge and discharge range of the battery cell to be a target SOC range. Wherein, the difference between the lower limit of the target SOC range and 0 is less than the difference between the upper limit of the target SOC range and 1.

[0023] Optionally, the lower limit of the target SOC range is equal to 0, and the product of the upper limit of the target SOC range and the first capacity is equal to the second capacity.

[0024] Optionally, the method further includes: when the battery cell meets the first condition, during the process of the power converter charging the battery cell, the battery management module increases the upper limit of the charging rate of the battery cell. The first condition includes at least one of the following: the cumulative charge of the battery cell within the first time period is less than the first charge threshold; the cumulative discharge of the battery cell within the second time period is less than the second charge threshold; the number of times that the discharge depth of the battery cell within the third time period is less than the first depth threshold is greater than the first number threshold; the number of times that the charge depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

[0025] Optionally, the method further includes: when the battery cell meets the second condition, during the process of the power converter charging the battery cell, the battery management module increases the upper limit of the discharging rate of the battery cell. The second condition includes at least one of the following: the cumulative charge of the battery cell within the first time period is less than the first charge threshold; the cumulative discharge of the battery cell within the second time period is less than the second charge threshold; the number of times that the discharge depth of the battery cell within the third time period is less than the first depth threshold is greater than the first number threshold; the number of times that the charge depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

[0026] In a third aspect, a battery pack is provided, which includes: a battery cell and a battery management module. Wherein, the capacity of the battery cell is the first capacity, and the first capacity refers to the actual capacity of the battery cell in the battery pack. The battery management module is used to control the charging capacity of the battery cell to be the second capacity and is used to control the discharging capacity of the battery cell to be the second capacity. The second capacity is less than the first capacity. And, the second capacity is the declared capacity of the battery pack.

[0027] Optionally, the above battery pack can be an energy storage battery pack, a power battery pack or a battery pack for 3C products.

[0028] Fourthly, a chip is provided, which is used to implement the control method of the energy storage system provided in the second aspect above.

[0029] Fifthly, a computer-readable storage medium is provided, in which instructions are stored, and the instructions are executed by a processor to implement the control method of the energy storage system provided in the second aspect above.

[0030] Sixthly, a computer program product containing instructions is provided. When the instructions run on a processor, the processor is caused to execute the control method of the energy storage system provided in the second aspect above.

[0031] In summary, the present application provides an energy storage system and its control method. The power converter in the energy storage system is used to charge and discharge the battery cells in the battery pack. The actual capacity of the battery cells in the battery pack is the first capacity, and the battery management module in the battery pack can control the charge and discharge capacity (i.e., the declared capacity) of the battery cells to be less than the first capacity during the process of the power converter charging and discharging the battery cells. Since there is a certain redundancy between the actual capacity of the battery cells and their charge and discharge capacity, the actual charge and discharge depth of the battery cells can be effectively reduced, and the actual charge and discharge depth of the battery cells can be avoided from reaching 100%. Also, since the deeper the charge and discharge depth of the battery cells, the faster the performance decay, the solution provided in the embodiments of the present application can effectively reduce the performance decay rate of the battery cells and extend the service life of the battery pack.

[0032] In addition, although the actual capacity of the battery cells in the battery pack is relatively large, since the available charge and discharge capacity (i.e., the declared capacity) provided for the customer is relatively small, the initial investment cost of the customer can be effectively avoided. And, since the actual capacity of the battery cells is greater than their declared capacity, even if the actual capacity of the battery cells decays with the increase of the usage time, it can be ensured that the charge and discharge capacity provided for the customer can always meet its declared capacity for a long time. That is, for the customer, the performance of the battery pack (such as the load-carrying time and load-carrying power) does not gradually decay compared with the initial performance, but can achieve long-term zero decay to ensure the consistent long-term experience of the customer. Description of the Drawings

[0033] Figure 1 is a schematic structural diagram of an energy storage system provided by an embodiment of the present application;

[0034] Figure 2 is a schematic structural diagram of a battery pack provided by an embodiment of the present application;

[0035] Figure 3 is a schematic control flow diagram of a battery management module provided by an embodiment of the present application;

[0036] Figure 4It is a schematic diagram showing the change of SOH of a battery pack over time provided by an embodiment of the present application;

[0037] Figure 5 It is a schematic structural diagram of another energy storage system provided by an embodiment of the present application;

[0038] Figure 6 It is a schematic diagram of a target SOC range provided by an embodiment of the present application;

[0039] Figure 7 It is a schematic diagram of another target SOC range provided by an embodiment of the present application;

[0040] Figure 8 It is a schematic diagram of the control flow of another battery management module provided by an embodiment of the present application;

[0041] Figure 9 It is a flowchart of a control method for an energy storage system provided by an embodiment of the present application. Detailed implementation manners

[0042] The energy storage system and its control method provided by the embodiments of the present application will be introduced in detail below with reference to the accompanying drawings.

[0043] The battery pack provided by the embodiments of the present application can be applied to an energy storage system. Figure 1 It is a schematic structural diagram of an energy storage system provided by an embodiment of the present application. As Figure 1 shown, the energy storage system may include: at least one battery pack 10 and a power converter 20. The power converter 20 may be a power conversion system (PCS). Among them, at least one battery pack 10 refers to one battery pack or a plurality of battery packs connected in series. Referring to Figure 1 , the at least one battery pack 10 is connected to the DC terminal of the power converter 20, and the AC terminal of the power converter 20 is used to connect to the power grid 30 and the load 40. The power converter 20 can convert the direct current provided by the at least one battery pack 10 into alternating current and output it to the power grid 30 and / or the load 40. And, the power converter 20 can also convert the alternating current provided by the power grid 20 into direct current and output it to the at least one battery pack 10 to charge the at least one battery pack 10.

[0044] Among them, each battery pack 10 may include at least one battery cell 11, for example, it may include a plurality of battery cells 11 connected in series and / or in parallel. The battery cell 11 may be a lithium-ion battery cell, for example, it may be a lithium iron phosphate battery cell or a ternary lithium battery cell, etc.

[0045] Optionally, the energy storage system may be a photovoltaic storage system, which may further include a photovoltaic module. The photovoltaic module is connected to the DC end of the power converter 20. The power converter 20 is also capable of converting the DC power of the photovoltaic module into AC power and outputting it to the power grid 30 and / or the load 40. In addition, the power converter 20 is also capable of performing power conversion on the DC power provided by the photovoltaic module and then charging the multiple battery packs 10.

[0046] In the absence of major breakthroughs in the current battery material system, the battery pack hardware capabilities are limited. As the battery pack is used longer and the number of charging cycles increases, the performance of the battery pack will gradually decline, and the customer experience will also decrease. For example, due to the deactivation of the negative electrode material particles of the battery pack due to shedding, and the irreversible deposition of lithium metal, the active lithium in the positive electrode of the battery pack will be consumed, thereby reducing the capacity and energy density of the battery pack.

[0047] In some cases, since the hardware configuration of the battery pack is fixed, some customers often use over-configuration to obtain considerable battery performance at the end of the battery pack's life, such as output power (i.e., load power), discharge capacity (i.e., load time), etc. In other words, customers will increase their initial investment to obtain better initial battery performance in order to cope with later performance degradation. However, this also means that the customer's initial cost will increase sharply and the benefits will decrease significantly.

[0048] In other embodiments, lithium replenishment technology (also called "pre-lithiation" or "pre-lithiation") is used to improve the performance of the battery pack. The lithium replenishment technology replenishes lithium ions by adding lithium to the battery pack before the battery pack is operated. The electrode material of the battery pack is replenished with lithium through pre-lithiation to offset the irreversible lithium loss, thereby increasing the life of the battery pack and the capacity decay cycle.

[0049] However, the technical maturity of lithium replenishment technology is relatively low, and the process complexity is extremely high. In addition, metallic lithium is highly active and has high requirements for environmental control. It requires the use of large-scale equipment, which has a relatively high cost investment and has a great impact on existing production processes. In addition, the use of metallic lithium also poses great safety risks, especially the risk of dust explosions caused by metallic lithium powder suspended in the air. Due to the above-mentioned process difficulties and safety risk limitations, lithium replenishment technology has not yet been applied in mass-produced battery packs.

[0050] The embodiment of the present application provides an energy storage system. The energy storage system provided by the embodiment of the present application can effectively delay the performance degradation of the battery pack in the energy storage system and increase the service life of the battery pack without increasing the initial investment of the customer and the complexity of the production process of the battery pack. Figure 1As shown in the figure, the energy storage system includes: a battery pack 10 and a power converter 20. One end (i.e., the DC end) of the power converter 20 is connected to the battery pack 10, and the other end (i.e., the AC end) of the power converter 20 is used to connect to the power grid 30 and the load 40. Figure 2 It is a schematic structural diagram of a battery pack provided by an embodiment of the present application. As Figure 2 shown, the battery pack 10 includes battery cells 11 and a battery management module 12. The power converter 20 is used to convert the power output by the power grid 30 and then charge the battery cells 11, and is also used to convert the power output by the battery cells 11 and then supply power to the load 40.

[0051] It can be understood that the energy storage system may include one or more battery packs 10. For example, it includes a plurality of series-connected battery packs 10. Each battery pack 10 may include one or more battery cells 11, and the plurality of battery cells 11 may be connected in series and / or in parallel. For example, the plurality of battery cells 11 may include a plurality of parallel-connected battery cell groups, and each battery cell group includes at least two series-connected battery cells 11.

[0052] In the embodiment of the present application, the capacity of the battery cells 11 in the battery pack 10 is the first capacity. The first capacity refers to the actual capacity of the battery cells 11. If the battery pack 10 includes a plurality of battery cells 11, then the first capacity refers to the sum of the actual capacities of the plurality of battery cells 11, that is, when the plurality of battery cells 11 are fully charged, the capacity of the battery pack 10.

[0053] The battery management module 12 is used to control the charging capacity of the battery cells 11 to be the second capacity during the process of the power converter 20 charging the battery cells 11, and is also used to control the discharging capacity of the battery cells 11 to be the second capacity during the process of the power converter 20 discharging the battery cells 11. The second capacity is less than the first capacity. Among them, the charging capacity of the battery cells 11 refers to the actual charge amount that the battery cells 11 are allowed to receive during charging; the discharging capacity of the battery cells 11 refers to the actual charge amount that the battery cells 11 are allowed to release during discharging. The above-mentioned second capacity can also be understood as the declared capacity or nominal capacity of the battery cells 11 in the battery pack 10. And, the second capacity is the capacity marked on the battery pack 10.

[0054] If the battery pack 10 includes a plurality of battery cells 11, then the above-mentioned second capacity may refer to the total charging capacity and total discharging capacity of the plurality of battery cells 11. And for each battery cell 11, the battery management module 12 can make the charging capacity and discharging capacity of the battery cell 11 less than its actual capacity.

[0055] Based on the above analysis, it can be seen that during the charging and discharging process of the battery cell 11, the battery management module 12 can control the charging and discharging capacity (i.e., the second capacity) of the battery cell 11 to be less than the actual capacity (i.e., the first capacity) of the battery cell 11 through software. Or it can be understood that: the actual capacity of the battery pack 10 has a certain redundancy compared to its declared capacity. Thus, it can effectively prevent the actual depth of discharge (DoD) and actual depth of charge (DoC) of the battery pack 10 from reaching 100%. In other words, the solution provided by the embodiments of the present application can effectively reduce the actual charging and discharging depth of the battery pack 10 and achieve shallow charging and discharging of the battery pack 10. Among them, the actual DoD of the battery pack 10 refers to the ratio of the discharge amount of the battery pack 10 to the actual capacity (i.e., the first capacity). The actual DoC of the battery pack 10 refers to the ratio of the charge amount of the battery pack 10 to the actual capacity (i.e., the first capacity).

[0056] Since the deeper the charging and discharging depth of the battery pack 10, the greater the charging and discharging power, and the heavier its load, which will accelerate the loss and aging process of the battery cell 11. Therefore, based on the above design of the embodiments of the present application, it can effectively reduce the performance attenuation rate of the battery pack 10, extend the service life of the battery pack 10, and ensure the consistency of the customer experience over a long period of time.

[0057] It can also be understood that although the actual capacity of the battery pack 10 is large, due to its relatively small declared capacity, that is, the available capacity provided by the battery pack 10 for customers is relatively small, the initial investment cost of customers can be avoided. And because the actual capacity of the battery pack 10 is greater than its declared capacity, even if the actual capacity of the battery pack 10 decays with the increase of use time, it can ensure that the charging and discharging capacity provided for customers can always meet its declared capacity for a long time. That is, for customers, the performance of the battery pack 10 (such as the load time and load power) will not gradually decay compared to the initial performance, but can achieve 0 decay in the long term to ensure the long-term consistent experience of customers.

[0058] For example Figure 3As shown in the figure, assume that the customer's requirement is that the performance of the battery pack 10 is X (for example, the capacity is X), and it stably outputs for A years. Then, in the product design of the solution provided by the embodiment of the present application, the hardware performance of the battery pack 10 can be configured as Y. For example, the actual capacity of the battery cell 11 in the battery pack 10 is configured as the first capacity Y. And, the battery management module 12 can control the output performance of the battery cell 11 in the battery pack 10 to be Z through a software control algorithm. For example, the charge and discharge capacity (i.e., the declared capacity) of the battery cell 11 in the battery pack 10 is controlled to be the second capacity Z, and it stably outputs for B years with the output performance Z. Wherein, B≥A, and the second capacity Z satisfies: X≤Z<Y. Based on this, during the actual use of the battery pack 10, since the upper limit of the performance configured by its hardware (i.e., performance Y) is not used, the performance of the battery pack 10 can be maintained without attenuation for a long time during the process of outputting with performance Z.

[0059] Figure 4 is a schematic diagram showing the change of the SOH of a battery pack provided by an embodiment of the present application over time. And, Figure 4 shows the SOH change curve of the battery pack 10 provided by the embodiment of the present application, and the SOH change curve of the battery pack without hardware redundancy design. Wherein, the hardware redundancy design means that the actual capacity of the battery pack is its declared capacity. And, it can be understood that the SOH of the battery pack can be characterized by the ratio of the actual available capacity of the battery pack to the declared capacity.

[0060] For the battery pack without hardware redundancy design, its actual capacity at the time of leaving the factory is the declared capacity. As the usage time of the battery pack increases, its actual available capacity will inevitably decay compared to the declared capacity, so the SOH of the battery pack will gradually decrease. By way of example, referring to Figure 4 it can be seen that the SOH of the battery pack at the time of leaving the factory is N%, for example, 100%, and its SOH will drop to M% after using it for B years, where M is less than N.

[0061] In the embodiment of the present application, however, the actual capacity Y of the battery pack 10 at the time of leaving the factory has a certain redundancy compared to the declared capacity Z. As the usage time of the battery pack 10 increases, its actual available capacity will also decay compared to the actual capacity Y. However, before the actual available capacity of the battery pack 10 decays to the declared capacity Z, its SOH can be stably maintained unchanged. By way of example, referring to Figure 4 it can be seen that the SOH of the battery pack 10 provided by the embodiment of the present application is N% at the time of leaving the factory, for example, 100%. Assume that its actual available capacity will decay to the declared capacity Z after using it for B years. Then, before B years, the SOH of the battery pack 10 can be maintained at the initial state (such as N%) without attenuation for a long time, thus effectively improving the customer's usage experience. In addition, it can be understood that, Figure 4The EOL in [context] refers to the SOH at the end of life of the battery pack. C years refers to the service life of the battery pack.

[0062] It can also be understood that Figure 4 The B years shown in [context], that is, the duration during which the performance of the battery pack 10 can be stably maintained, can be calculated based on the performance decay curve of the battery pack 10 after considering the influence of different working conditions on the service life of the battery pack. As described above, the solution provided by the embodiments of the present application can effectively reduce the actual charge and discharge depth of the battery cell 11, that is, its actual working conditions are relatively good, so the duration during which its performance can be stably maintained is usually longer than the evaluated B years.

[0063] Based on the above analysis, it can be seen that the solution provided by the embodiments of the present application makes a redundant design for the capacity of the battery pack in terms of hardware, and then through software regulation to ensure that the product has a longer service life while maintaining stable performance for a long time. That is, through the reasonable configuration of the hardware base and the coordination of the upper-layer software, the customer does not perceive the battery performance decay within a relatively long period of time, ensuring that the product value is utilized to the greatest extent.

[0064] In the embodiments of the present application, the difference between the first capacity and the second capacity (i.e., the redundant capacity of the battery pack) can be flexibly set according to the requirements of the application scenario. For example, the redundant capacity can be 20% to 30% of the first capacity, that is, the second capacity can be 70% to 80% of the first capacity.

[0065] Optionally, referring to Figure 5 , the energy storage system may further include a BCU 50, and the BCU 50 may establish a communication connection with the battery management module 12 in the battery pack 10. By way of example, the battery management module 12 in the battery pack 10 may be a BMU. The BCU 50 and the BMUs in each battery pack 10 in the energy storage system may form a BMS. And, as Figure 5 shown, the BCU 50 may be disposed in the cluster control box.

[0066] In the embodiments of the present application, the BCU 50 is used to send an instruction to the battery management module 12 in the battery pack 10. The instruction is used to unlock the redundant capacity of the battery pack 10, and this instruction may also be referred to as an unlocking instruction.

[0067] The battery management module 12 is further configured to adjust both the charging capacity and the discharging capacity of the battery cell 11 to a third capacity based on the received instruction. That is, adjust the declared capacity (or nominal capacity) of the battery pack 10 to the third capacity. The third capacity is greater than the second capacity and less than or equal to the first capacity. That is, the battery management module 12 can release part or all of the redundant capacity of the battery cell 11, thereby achieving the effect of increasing the capacity of the battery pack 10.

[0068] In the solution provided by the embodiments of the present application, the battery management module 12 can dynamically adjust the charging capacity and discharging capacity of the battery cells 11 in the battery pack 10, that is, dynamically adjust the actual available capacity of the battery pack 10, thereby effectively improving the usage flexibility of the battery pack 10 to meet the requirements of different application scenarios.

[0069] Among them, the instruction can be sent by the server of the energy storage system, that is, the server can instruct the battery management module 12 to adjust both the charging capacity and the discharging capacity of the battery cell 11 to a third capacity through the instruction. Optionally, the server can send an instruction to the battery management module 12 based on over-the-air (OTA) technology, such as sending a software license, so as to update (or upgrade) the software algorithm of the battery management module 12, so that the battery management module 12 releases part or all of the redundant capacity of the battery cell 11.

[0070] Exemplarily, assuming that the battery management module 12 is the BMU in the energy storage system, the BCU in the energy storage system can receive the instruction sent by the server and then send the instruction to the BMU in the battery pack 10.

[0071] It can be understood that the service life of the battery pack 10 is usually relatively long. For example, the service life of an energy storage battery pack is often 10 years or even 15 years. During this period, the customer's required power consumption is almost never constant. After purchasing the battery pack, there may be a situation where the required power consumption increases due to reasons such as changes in the usage scenario. At this time, the customer can unlock the redundant power in the hardware performance configuration of the battery pack 10 by paying for the software license, achieving the effect of increasing the capacity of the battery pack 10. In this process, since the customer only needs to operate the software without adding or modifying hardware devices, the efficiency of increasing the capacity of the battery pack 10 can be effectively improved, and the customer's workload can be significantly reduced.

[0072] Optionally, the battery management module 12 can also be used to control the charge and discharge interval of the battery cell 11 to a target SOC interval, that is, control the battery cell 11 to charge or discharge within the target SOC interval. It can be understood that the SOC of the battery cell 11, also known as the remaining power, refers to the ratio of the remaining capacity of the battery cell 11 to the rated capacity. As Figure 6 shown, the value range of SOC is from 0 to 1. In the embodiments of the present application, the above target SOC interval is calculated using the actual capacity (i.e., the first capacity) of the battery cell 11 in the battery pack 10 as the rated capacity.

[0073] Moreover, in the embodiments of the present application, the difference between the lower limit of the target SOC range and 0 is less than the difference between the upper limit of the target SOC range and 1. That is to say, the target SOC range is closer to 0, that is, the target SOC range is a low SOC range. It can be seen that the battery management module 12 can control the battery pack 10 to continuously operate in the low SOC range, that is, control the battery pack 10 to continuously charge and discharge at the end of the first capacity. It can be understood that the battery pack 10 operating in the low SOC range may mean that each battery cell 11 in the battery pack 10 operates in its respective low SOC range. Since the attenuation of the battery cell 11 during long-term operation in the low SOC range is smaller than that in the high SOC range, based on the above design of the embodiments of the present application, the performance attenuation of the battery cell 11 can be effectively alleviated, and the service life of the battery pack 10 can be extended.

[0074] It can also be understood that the size of the above target SOC range (that is, the difference obtained by subtracting the lower limit from the upper limit) can be determined according to the second capacity. And the product of the size of the target SOC range and the first capacity is equal to the second capacity. By way of example, assuming that the actual capacity (i.e., the first capacity) of the battery pack 10 is 20 kilowatt-hours (kWh), and the declared capacity (i.e., the second capacity) is 15 kWh, then the size of the target SOC range can be 75%. By way of example, referring to Figure 6 , the lower limit of the target SOC range can be 5%, and the upper limit can be 80%, that is, the battery management module 12 can control the battery pack 10 to perform charge and discharge cycles in the range of 5% to 80% of the actual capacity.

[0075] Optionally, the lower limit of the target SOC range can be equal to 0. Correspondingly, the product of the upper limit of the target SOC range and the first capacity is equal to the second capacity. By setting the lower limit of the target SOC range to 0, the battery cells 11 in the battery pack 10 can operate in the lowest possible SOC range, thereby effectively slowing down their performance attenuation. By way of example, for a scenario where the first capacity is 20 kWh and the second capacity is 15 kWh, as Figure 7 shown, the upper limit of the target SOC range is 75%, that is, the battery management module 12 can control the battery cells 11 to perform charge and discharge cycles in the range of 0% to 75% of the actual capacity.

[0076] Optionally, the battery cells 11 in the battery pack 10 can be lithium iron phosphate battery cells. Based on the characteristics of lithium iron phosphate battery cells, it can be known that the voltage of the battery cells changes significantly in the low SOC range and the high SOC range, that is, the voltage of the battery cells changes significantly with the capacity of the battery cells. Among them, the low SOC range is also called the low power range, or the discharge end range. The high SOC range is also called the range close to full charge, or the charge end range.

[0077] In the non-charge / discharge end region (i.e., the middle capacity section, also known as the middle state of charge range), the change in the cell voltage with respect to the cell capacity is not obvious. Since the calibration of the SOX parameter of the battery pack 10 relies on the characterization of the battery pack 10's performance by the cell voltage, if the middle capacity section of the cell 11 is used for charge and discharge, it is impossible to reach the charge end range or the discharge end range. After the cell 11 has been charged and discharged in this middle capacity section for a long time, it will cause a serious decline in the accuracy of the SOX of the battery pack 10, affecting the customer experience.

[0078] If the upper capacity of the cell 11, i.e., the range close to the charge end, is used for charge and discharge, a more accurate SOX can be obtained at the charge end. However, since the cell 11 will spend more time in the high state of charge (SOC) range for charge and discharge cycles, it is not friendly to the cell life. Also, if the cell 11 fails (such as thermal runaway) in the high SOC range, more serious consequences will occur.

[0079] Based on the above analysis, in the embodiment of the present application, the battery management module 12 can control the cell 11 in the battery pack 10 to operate in the low SOC range, that is, control the cell 11 to charge and discharge at the lower end of its actual capacity. Thus, on the one hand, accurate SOX calibration can be performed at the discharge end to ensure a better customer experience. On the other hand, since the cell 11 in the battery pack 10 operates in a relatively low SOC range for a long time, the performance degradation of the cell 11 is smaller and it is more friendly to the life. On the other hand, compared with the high SOC range, the impact after the battery pack 10 fails in the low SOC range is smaller and its safety is higher.

[0080] It can be understood that the SOX described above can include state of charge (SOC), state of health (SOH), state of power (SOP), state of energy (SOE), etc.

[0081] Optionally, the battery management module 12 is further configured to increase the upper limit of the charging rate of the cell 11 during the charging process of the power converter 20 when the cell 11 meets the first condition. Wherein, the first condition may include at least one of the following:

[0082] The cumulative charge of the cell 11 within the first time period is less than the first charge threshold;

[0083] The cumulative discharge of the cell 11 within the second time period is less than the second charge threshold;

[0084] The number of times the discharge depth of the cell 11 within the third time period is greater than the first depth threshold is less than the first number threshold;

[0085] The number of times the charge depth of the cell 11 within the fourth time period is greater than the second depth threshold is less than the second number threshold.

[0086] It can be understood that the cumulative charge and cumulative discharge of the battery cells 11 in the battery pack 10 within a certain period of time can also be referred to as the throughput power of the battery pack 10. Based on the above first condition, it can be known that the battery management module 12 can increase the upper limit of the charging rate of the battery cell 11 when it detects that the throughput power of the battery pack 10 is low within a certain period of time, or when the charging depth or discharge depth is shallow within a certain period of time, that is, increase the maximum charging rate of the battery cell 11. Among them, the charging rate = charging current / declared capacity (nominal capacity). Based on the definition of the charging rate, increasing the upper limit of the charging rate of the battery cell 11 also means increasing the upper limit of the charging current of the battery cell 11 (that is, increasing the maximum charging current), that is, increasing the upper limit of the input power of the battery cell 11 (that is, increasing the maximum input power). By increasing this charging rate, the charging speed of the battery pack 10 can be effectively improved, and the charging duration of the battery pack 10 can be shortened.

[0087] It can also be understood that the above first duration, second duration, third duration, and fourth duration can be equal or unequal. Moreover, each of the above durations can be flexibly configured according to the requirements of the application scenario. For example, the above first duration, second duration, third duration, and fourth duration can all be 1 month, or can be multiple months.

[0088] The above first power threshold and second power threshold can be equal or unequal. Moreover, the first power threshold and the second power threshold can also be flexibly configured according to the requirements of the application scenario. For example, both the first power threshold and the second power threshold are greater than the first capacity, and the first power threshold can be proportional to the first duration and the first capacity, and the second power threshold can be proportional to the second duration and the first capacity.

[0089] The above first depth threshold and second depth threshold can be equal or unequal. Moreover, the first depth threshold and the second depth threshold can also be flexibly configured according to the requirements of the application scenario. For example, the value ranges of both the first depth threshold and the second depth threshold can be from 80% to 100%, for example, can be 90%.

[0090] The above first number threshold and second number threshold can be equal or unequal. Moreover, the first number threshold and the second number threshold can also be flexibly configured according to the requirements of the application scenario and according to the values of the above third duration and fourth duration. For example, assuming that both the third duration and the fourth duration are 1 month, then both the first number threshold and the second number threshold can be 1 or 2.

[0091] Based on the above analysis, when the battery management module 12 detects that the operating conditions of the battery cells 11 in the battery pack 10 meet the above first condition, it can determine that the usage frequency of the battery pack 10 is relatively low, or the charge-discharge depth is relatively shallow. For example, it can be determined that the battery pack 10 has not been fully charged or discharged for a long time. Since the performance decay of the battery pack 10 is slower under the above operating conditions, the duration during which its performance is stably maintained at the initial performance is longer than the estimated duration (such as B years). At this time, the battery management module 12 can increase the upper limit of the charging rate of the battery cells 11 in the battery pack 10, that is, release some redundant performance of the battery cells 11. For example, assuming that the initial upper limit of the charging rate of the battery cell 11 is 0.5C, the battery management module 12 can increase the upper limit of the charging rate of this battery cell 11 to 0.6C. Thus, on the basis of meeting the stable output duration required by the customer, the performance of the battery cells 11 can be effectively improved to short-term adapt to the excessive demand of the customer and enhance the customer experience.

[0092] Optionally, the battery management module 12 is further configured to increase the upper limit of the discharge rate of the battery cell 11 during the discharge process of the power converter 20 to the battery cell 11 when the battery cell 11 meets the second condition. The second condition may include at least one of the following:

[0093] The cumulative charge of the battery cell 11 within the first duration is less than the first charge threshold;

[0094] The cumulative discharge of the battery cell 11 within the second duration is less than the second charge threshold;

[0095] The number of times that the discharge depth of the battery cell 11 within the third duration is greater than the first depth threshold is less than the first number threshold;

[0096] The number of times that the charge depth of the battery cell 11 within the fourth duration is greater than the second depth threshold is less than the second number threshold.

[0097] Among them, the discharge rate = discharge current / declared capacity (nominal capacity). Based on the definition of the discharge rate, increasing the upper limit of the discharge rate of the battery cell 11 means increasing the upper limit of the discharge current of the battery cell 11 (i.e., increasing the maximum discharge current), that is, increasing the upper limit of the output power of the battery cell 11 (i.e., increasing the maximum output power). By increasing this discharge rate, the discharge speed of the battery pack 10 can be effectively increased to meet the short-term high-load demand.

[0098] It can be understood that the above second condition may be the same as or different from the first condition, and the embodiments of the present application do not limit this. Moreover, based on the foregoing analysis, when the battery management module 12 detects that the operating conditions of the battery cells 11 in the battery pack 10 meet the above second condition, it can be determined that the usage frequency of the battery pack 10 is relatively low, or the charge-discharge depth is relatively shallow. For example, it can be determined that the battery pack 10 has not been fully charged or discharged for a long time. Since the performance degradation of the battery pack 10 is slower under the above operating conditions, the duration during which the performance is stably maintained at the initial performance is longer than the estimated duration (e.g., B years). At this time, the battery management module 12 can increase the upper limit of the discharge rate of the battery cells 11 in the battery pack 10, that is, release part of the redundant performance of the battery cells 11. For example, assuming that the initial upper limit of the charge rate of the battery cell 11 is 0.5C, the battery management module 12 can increase the upper limit of the charge rate of this battery cell 11 to 0.6C. Thus, on the basis of meeting the stable output duration required by the customer, the performance of the battery cells 11 can be effectively improved to short-term adapt to the excessive demand of the customer and enhance the customer experience.

[0099] Exemplarily, referring to Figure 8 , assume that the customer's requirement is that the performance of the battery pack 10 is X (for example, the capacity is X1, and the upper limits of the discharge rate and the charge rate are both X2), and the stable output is A years. Then, in the product design of the solution provided by the embodiments of the present application, the hardware performance of the battery pack 10 can be configured as Y. For example, the actual capacity of the battery cells 11 in the battery pack 10 can be configured as the first capacity Y1, and the upper limits of the discharge rate and the charge rate can be configured as Y2. Moreover, the battery management module 11 can control the output performance of the battery cells 11 in the battery pack 10 to be Z through a software control algorithm. For example, control the charge-discharge capacity (i.e., the declared capacity) of the battery cells 11 to be the second capacity Z1, control the upper limits of the discharge rate and the charge rate to be Z2, and the battery cells 11 can stably output for B years with the output performance Z. Among them, the second capacity Z1 satisfies: X1 ≤ Z1 < Y1, and the upper limits of the discharge rate and the charge rate Z2 satisfy: X2 ≤ Z2 < Y2.

[0100] After that, during the actual operation of the battery pack 10, the battery management module 12 can monitor the hardware operating conditions of the battery cells 11 in the battery pack 10 in real time. For example, it can detect the DoD, DoC, and / or throughput power of the battery pack 10, etc. If it is detected that the hardware operating conditions of the battery pack 10 meet the above first condition or second condition, the battery management module 12 can adjust the performance of the battery cells 11 in the battery pack 10 to W through software. For example, control and adjust the upper limits of the discharge rate and the charge rate of this battery cell 11 to be both W, and W satisfies: Z2 < W ≤ Y2. After that, the battery management module 12 can control the battery cells 11 to stably output for A years according to the performance W. Thus, on the basis of meeting the performance stable output duration required by the customer, the performance of the battery cells 11 can be effectively improved, thereby enhancing the customer experience.

[0101] It can also be understood that, since the actual performance of the battery pack 10 has a certain redundancy compared to the performance it provides to customers, the charge and discharge power of the battery pack 10 can be made relatively small. Accordingly, when the battery management module 12 detects that the hardware usage condition of the battery pack 10 meets the above first condition or second condition, some redundant performance can be released to meet the short-term high-load demand of customers.

[0102] In summary, the embodiment of the present application provides an energy storage system. The power converter in the energy storage system is used to charge and discharge the battery cells in the battery pack. Among them, the actual capacity of the battery cells in the battery pack is the first capacity, and the battery management module in the battery pack can control the charge and discharge capacity of the battery cells to be less than the first capacity during the process of the power converter charging and discharging the battery cells. Since the actual capacity of the battery cells has a certain redundancy compared to their charge and discharge capacity, the actual charge and discharge depth of the battery cells can be effectively reduced, and the actual charge and discharge depth of the battery cells can be prevented from reaching 100%. Also, since the deeper the charge and discharge depth of the battery cells, the faster the performance degradation, the solution provided by the embodiment of the present application can effectively reduce the performance degradation rate of the battery cells and extend the service life of the battery pack. Accordingly, the battery pack can provide customers with more capacity and a longer backup power time, achieve performance maximization, and ensure that customers have a better experience. For example, the household energy storage product can provide customers with overnight load usage.

[0103] Moreover, the battery management module can also dynamically adapt to the electricity consumption needs of customers through software allocation during the long-term zero-decay cycle of the battery cells, and increase the capacity of the battery cells to a certain extent to meet the growing electricity consumption needs of customers.

[0104] The embodiment of the present application also provides a control method for an energy storage system. This control method can be applied to the energy storage system provided in the above embodiment. As Figure 1 and Figure 2 shown, this energy storage system includes a battery pack and a power converter. The battery pack includes battery cells and a battery management module. Among them, one end of the power converter is connected to the battery pack, and the other end is connected to the power grid and the load. And this power converter is used to convert the power output by the power grid and then charge the battery cells, and is used to convert the power output by the battery cells and then supply power to the load.

[0105] The control method for the energy storage system provided by the embodiment of the present application can be executed by the battery management module in the battery pack. As Figure 9 shown, this control method includes:

[0106] Step 101, during the process of the power converter charging the battery cells, control the charging capacity of the battery cells to be the second capacity.

[0107] Step 102: During the process of the power converter discharging the battery cell, control the discharge capacity of the battery cell to be the second capacity.

[0108] As described above, the actual capacity of the battery cell in the battery pack is the first capacity. The battery management module can control both the charging capacity and the discharge capacity of the battery cell to be the second capacity during the charging and discharging process of the power converter for the battery cell. This second capacity is less than the first capacity. That is, the second capacity provided by the battery cell to the customer is less than its actual capacity of the hardware configuration. Thus, on the one hand, it can effectively reduce the charge-discharge depth of the battery pack, thereby slowing down the performance degradation of the battery pack; on the other hand, it can ensure that the performance provided to the customer remains stable without degradation before the actual capacity of the battery pack decays to the second capacity.

[0109] Optionally, as Figure 5 shown, the energy storage system further includes a BCU, which can send an instruction to the battery management module in the battery pack, and this instruction is used to unlock (i.e., release) the redundant capacity of the battery pack. Continuing to refer to Figure 9 , the method further includes:

[0110] Step 103: Based on the instruction sent by the BCU, adjust both the charging capacity and the discharge capacity of the battery cell to be the third capacity.

[0111] Among them, this third capacity is greater than the second capacity and less than or equal to the first capacity. This instruction can be sent from the server of the energy storage system to the BCU, and the server can send this instruction based on the customer's capacity expansion requirement. Thus, it can achieve the capacity expansion of the battery pack without the need to add or transform hardware devices.

[0112] Optionally, the above step 101 may include: controlling the charging range of the battery cell to be the target state of charge (SOC) range of the first capacity. The above step 102 may include: controlling the discharge range of the battery cell to be the target state of charge (SOC) range of the first capacity. Among them, the difference between the lower limit of the target SOC range and 0 is less than the difference between the upper limit of the target SOC range and 1. That is, this target SOC range is a low SOC range. By controlling the battery cells in the battery pack to continuously operate in the low SOC range, the performance degradation of the battery cells can be effectively alleviated and the service life of the battery cells can be extended.

[0113] Optionally, the lower limit of this target SOC range may be equal to 0, and the product of the upper limit of the target SOC range and the first capacity is equal to the second capacity. By setting the lower limit of this target SOC range to 0, the battery cell can operate in the lowest possible SOC range, thereby effectively slowing down its performance degradation.

[0114] Optionally, as Figure 9 shown, the method may further include:

[0115] Step 104: When the battery cell meets the first condition, during the process of the power converter charging the battery cell, increase the upper limit of the charging rate of the battery cell.

[0116] Among them, the first condition may include at least one of the following:

[0117] The cumulative charge of the battery cell within the first time period is less than the first charge threshold;

[0118] The cumulative discharge of the battery cell within the second time period is less than the second charge threshold;

[0119] The number of times that the discharge depth of the battery cell within the third time period is greater than the first depth threshold is less than the first number threshold;

[0120] The number of times that the charge depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

[0121] Optionally, as Figure 9 shown, the method may further include:

[0122] Step 105: When the battery cell meets the second condition, during the process of the power converter discharging the battery cell, increase the upper limit of the discharge rate of the battery cell.

[0123] Among them, the second condition includes at least one of the following:

[0124] The cumulative charge of the battery cell within the first time period is less than the first charge threshold;

[0125] The cumulative discharge of the battery cell within the second time period is less than the second charge threshold;

[0126] The number of times that the discharge depth of the battery cell within the third time period is greater than the first depth threshold is less than the first number threshold;

[0127] The number of times that the charge depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

[0128] It can be understood that in the above control method of the energy storage system, the sequence of each step can be appropriately adjusted, and the steps can also be increased or decreased accordingly according to the situation. For example, at least one of the above steps 103 to 105 can be deleted according to the situation, or the above step 102 can be executed before step 101, or the above step 104 and / or step 105 can be executed before step 103.

[0129] It can also be understood that the above control method of the energy storage system has basically the same implementation manner and technical effect as the energy storage system provided in the foregoing embodiment. Therefore, for the sake of simplicity, the implementation manner and technical effect of the control method of the energy storage system are not repeated here.

[0130] An embodiment of the present application further provides a battery pack, as Figure 2 shown. The battery pack 10 includes a battery cell 11 and a battery management module 12. Among them, the capacity of the battery cell 11 is a first capacity. The first capacity refers to the actual capacity of the battery cell 11.

[0131] The battery management module 12 is used to control the charging capacity of the battery cell 11 to be a second capacity, and is used to control the discharging capacity of the battery cell 11 to be the second capacity. The second capacity is less than the first capacity. Among them, the charging capacity of the battery cell 11 refers to the actual charge amount that the battery cell 11 allows to receive during charging; the discharging capacity of the battery cell 11 refers to the actual charge amount that the battery cell 11 allows to release during discharging. The above-mentioned second capacity can also be understood as the declared capacity or nominal capacity of the battery cell 11 in the battery pack 10. And, the second capacity is the capacity marked on the battery pack 10.

[0132] It can be understood that for the implementation of the functions of the battery management module 12, reference can also be made to the relevant descriptions in the foregoing embodiment of the energy storage system, which will not be elaborated here.

[0133] It can also be understood that the battery pack 10 provided by the embodiment of the present application can be applied not only to the energy storage system, but also to other fields. For example, it can also be applied to the field of power batteries or to 3C products. Among them, 3C products refer to computer, communication, and consumer electronic products.

[0134] Among them, if the battery pack 10 is applied to the energy storage system, the above-mentioned battery management module 12 can be a BMU. If the battery pack 10 is applied to fields such as power batteries or 3C products, the above-mentioned battery management module 12 can be a battery management system (BMS).

[0135] It can also be understood that in the battery pack 10 provided by the embodiment of the present application, the battery cell 11 and the battery management module 12 can be encapsulated in one housing. Or, the battery cell 11 and the battery management module 12 can be independently encapsulated, that is, the battery cell 11 and the battery management module 12 can be two independent (i.e., separated) modules. The embodiment of the present application does not limit the encapsulation method of the battery cell 11 and the battery management module 12.

[0136] An embodiment of the present application further provides a computer-readable storage medium. Instructions are stored in the computer-readable storage medium. When the instructions run in the battery management module, the battery management module is caused to execute the control method of the energy storage system provided in the foregoing method embodiment.

[0137] The embodiments of the present application also provide a computer program product containing instructions. When the instructions run in the battery management module, the battery management module is caused to execute the control method of the energy storage system provided in the above method embodiments.

[0138] The embodiments of the present application also provide a chip for implementing the control method of the energy storage system provided in the above method embodiments. The chip can be a BMU, for example, it can be a battery management integrated circuit (abbreviated as BMIC). Alternatively, the chip can be a BMS chip.

[0139] In the embodiments of the present application, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. The term "at least one" means one or more, and "a plurality" means two or more.

[0140] In the embodiments of the present application, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0141] As mentioned above, the above are only optional embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An energy storage system, characterized in that: The energy storage system comprises: a battery pack and a power converter; wherein the battery pack comprises: a battery cell and a battery management module, and the capacity of the battery cell is a first capacity; One end of the power converter is connected to the battery pack, and the other end of the power converter is used to connect the power grid and the load. The power converter is used to charge the battery cell after power conversion on the power output of the power grid, and to power the load after power conversion on the power output of the battery cell; The battery management module is used to control the charging capacity of the battery cell to be a second capacity when the power converter is charging the battery cell, and is used to control the discharging capacity of the battery cell to be the second capacity when the power converter is discharging the battery cell, and the second capacity is smaller than the first capacity.

2. The energy storage system according to claim 1, characterized in that: The energy storage system further includes: a battery control unit BCU, the BCU establishing a communication connection with a battery management module in the battery pack and used to issue instructions to the battery management module; The battery management module is further configured to adjust the charging capacity and the discharging capacity of the battery cell to a third capacity based on the received instruction, where the third capacity is greater than the second capacity and less than or equal to the first capacity.

3. The energy storage system according to claim 1 or 2, characterized in that: The battery management module is further used to control the charging and discharging interval of the battery cell to be a target state of charge SOC interval; The difference between the lower limit of the target SOC interval and 0 is smaller than the difference between the upper limit of the target SOC interval and 1.

4. The energy storage system according to claim 3, characterized in that: A lower limit of the target SOC interval is equal to 0, and a product of an upper limit of the target SOC interval and the first capacity is equal to the second capacity.

5. The energy storage system according to any one of claims 1 to 4, characterized in that: The battery management module is further configured to increase an upper limit of a charging rate of the battery cell during a process in which the power converter charges the battery cell when the battery cell meets a first condition, wherein the first condition includes at least one of the following: The accumulated charge amount of the battery cell within the first time period is less than the first charge threshold; The accumulated discharge amount of the battery cell within the second time period is less than the second power threshold; The number of times that the discharge depth of the battery cell within the third time period is greater than the first depth threshold is less than the first number threshold; The number of times that the charging depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

6. The energy storage system according to any one of claims 1 to 5, characterized in that: The battery management module is further configured to increase an upper limit of a discharge rate of the battery cell during discharge of the battery cell by the power converter when the battery cell meets a second condition, wherein the second condition includes at least one of the following: The accumulated charge amount of the battery cell within the first time period is less than the first charge threshold; The accumulated discharge amount of the battery cell within the second time period is less than the second power threshold; The number of times that the discharge depth of the battery cell within the third time period is greater than the first depth threshold is less than the first number threshold; The number of times that the charging depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

7. The energy storage system according to any one of claims 1 to 6, characterized in that: The battery cell is a lithium iron phosphate battery cell.

8. A control method for an energy storage system, characterized in that: The energy storage system comprises: a battery pack and a power converter; wherein the battery pack comprises a battery cell and a battery management module, and the capacity of the battery cell is a first capacity; one end of the power converter is connected to the battery pack, and the other end of the power converter is used to connect a power grid and a load, and the power converter is used to charge the battery cell after power conversion of the power output by the power grid, and to power the load after power conversion of the power output by the battery cell; the method comprises: In the process of the power converter charging the battery cell, the battery management module controls the charging capacity of the battery cell to be a second capacity; During the process of the power converter discharging the battery cell, the battery management module controls the discharge capacity of the battery cell to be the second capacity, and the second capacity is smaller than the first capacity.

9. The method according to claim 8, characterized in that The energy storage system further includes: a BCU, wherein the BCU establishes a communication connection with the battery management module; and the method further includes: The BCU sends instructions to the battery management module; The battery management module adjusts the charging capacity and the discharging capacity of the battery cell to a third capacity based on the received instruction; The third capacity is greater than the second capacity and less than or equal to the first capacity.

10. The method according to claim 8 or 9, characterized in that: The method further comprises: The battery management module controls the charge and discharge interval of the battery cell to be the target SOC interval of the first capacity; The difference between the lower limit of the target SOC interval and 0 is smaller than the difference between the upper limit of the target SOC interval and 1.

11. The method according to claim 10, characterized in that A lower limit of the target SOC interval is equal to 0, and a product of an upper limit of the target SOC interval and the first capacity is equal to the second capacity.

12. The method according to any one of claims 8 to 11, characterized in that: The method further comprises: When the battery cell meets a first condition, during the process of the power converter charging the battery cell, the battery management module increases an upper limit of a charging rate of the battery cell, wherein the first condition includes at least one of the following: The accumulated charge amount of the battery cell within the first time period is less than the first charge threshold; The accumulated discharge amount of the battery cell within the second time period is less than the second power threshold; The number of times that the discharge depth of the battery cell within the third time period is less than the first depth threshold is greater than the first number threshold; The number of times that the charging depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

13. The method according to any one of claims 8 to 12, characterized in that: The method further comprises: When the battery cell meets a second condition, the battery management module increases an upper limit of a discharge rate of the battery cell during discharge of the battery cell by the power converter, wherein the second condition includes at least one of the following: The accumulated charge amount of the battery cell within the first time period is less than the first charge threshold; The accumulated discharge amount of the battery cell within the second time period is less than the second power threshold; The number of times that the discharge depth of the battery cell within the third time period is less than the first depth threshold is greater than the first number threshold; The number of times that the charging depth of the battery cell within the fourth time period is greater than the second depth threshold is less than the second number threshold.

Images