A method for parallel connection of energy storage system with multiple LLCs

Abstract

The present application proposes a method for paralleling a multi-LLC parallel energy storage system, wherein the energy storage system includes a plurality of battery packs with built-in LLCs. The method for paralleling a multi-LLC parallel energy storage system determines whether the battery pack voltage is normal and checks the connection status to ensure that the system is in the correct state, and then performs different operations according to the operating state of the energy storage system: in the standby state, wait for charging or discharging instructions; in the charging state, balance the power of the battery packs and re-power them all in order from low to high; in the discharging state, determine the number of parallel battery packs according to the required power, and power them on in order from high to low voltage. The present invention solves the problem of capacity differences between different battery packs, avoids the situation where battery packs cannot be used at the same time, effectively prevents the battery circulation problem caused by capacity mismatch, and ensures the stability of the battery packs when they are paralleled. By optimizing energy distribution, the overall performance of the system is improved, allowing the energy storage system to operate more efficiently.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage batteries, and in particular to a method for parallel connection of a multi-LLC energy storage system. Background Art

[0002] In a home energy storage system, in order to match low-power batteries with high-voltage inverters, it is usually necessary to boost the voltage of the battery pack. When designing a system, multiple battery packs are often connected in parallel to meet the inverter's needs by boosting the voltage.

[0003] However, this parallel battery pack design also brings a key problem - voltage imbalance between battery packs. Since the voltage of each battery pack and the characteristics of the internal cells are different, when running in parallel, the discharge current and voltage of different battery packs will be different due to factors such as line loss and temperature differences. This imbalance will cause some battery packs to over-discharge, while other battery packs may not be fully discharged, which will affect the efficiency and safety of the entire system.

[0004] Over time, this battery pack imbalance problem will gradually intensify, causing the discharge depth of some battery packs to decrease, which in turn affects the overall performance and service life of the battery. Battery packs that are in an unbalanced state for a long time may cause damage to the cells, and may even cause the entire battery pack to fail. In addition, even if a single battery pack fails, it may affect the stability of the entire system and even cause the entire home energy storage system to fail to operate normally.

[0005] This battery imbalance problem not only greatly reduces the redundancy and reliability of the system, but also increases the maintenance cost and usage cost of the system. Summary of the invention

[0006] In order to solve the above technical problems, the present application proposes a method for parallel connection of a multi-LLC parallel energy storage system. By using a bidirectional LLC converter, not only can the voltage be increased or decreased, but also the battery pack can be charged and discharged.

[0007] In a first aspect, the present application proposes a parallel connection method for a multi-LLC energy storage system, wherein the energy storage system includes a plurality of battery packs with built-in LLCs, and the parallel connection method for the energy storage system specifically includes: S1: Determine whether the voltage of each battery pack in the energy storage system is within a normal range. If so, proceed to step S2; otherwise, check the connection status of the battery pack and execute step S1 again; S2: Obtain the current operating status of the energy storage system. If the energy storage system is in a standby state, wait for a charge and discharge instruction; if the energy storage system is in a charging state, proceed to step S3; if the energy storage system is in a discharging state, proceed to step S4; S3: Obtain the remaining power of all battery packs in the energy storage system, calculate the difference in remaining power between all battery packs in the energy storage system, perform strategy processing according to the maximum difference in remaining power, until the difference in remaining power between all battery packs in the energy storage system is less than a preset difference, and then re-power on all battery packs in order from low to high voltage; S4: Obtain the power demand of the device, determine the number of battery packs that need to be connected in parallel according to the power demand, and then power on the battery packs in descending order of voltage.

[0008] This application effectively avoids system failures caused by abnormal battery packs by judging in real time whether the voltage of each battery pack is within the normal range, and checking and retrying when the voltage is abnormal. This can ensure the stability of the entire energy storage system and avoid potential safety hazards. In the charging state, the system automatically obtains the remaining power of all battery packs and performs balanced charging to ensure that the power of all battery packs is balanced. This charging strategy helps to extend the service life of the battery pack and avoid excessive discharge or overcharging caused by uneven battery power, thereby improving the efficiency and safety of the system; in the discharge state, the system automatically determines the number of battery packs that need to be connected in parallel according to the required power of the equipment, and powers on the battery packs in order from high to low voltage, thereby ensuring the flexible response of the system under different load requirements, optimizing the use efficiency of the battery pack, and ensuring the stability of power supply. The system gives priority to starting the battery pack with higher voltage according to the voltage difference of the battery pack, and reasonably allocates energy storage resources, thereby achieving efficient and uniform battery pack paralleling. This paralleling method can meet different power requirements while avoiding over-reliance on certain battery packs, improving the overall operating efficiency and stability of the system.

[0009] Furthermore, the step S3 includes: S31: Determine the difference in remaining power among all battery packs in the energy storage system. If the maximum remaining power difference is less than the first preset difference, proceed to step S34. If the maximum remaining power difference is greater than the first preset difference, charge the battery pack with the smallest remaining power and proceed to step S32. S32: when the remaining power of the battery pack currently being charged is the largest among all the battery packs, determining the maximum difference in the remaining power among all the battery packs in the energy storage system, and if the current maximum difference in the remaining power is greater than a second preset difference, powering off the battery pack currently being charged, and powering on the battery pack with the smallest remaining power for charging; S33: repeating step S32 until the difference in the remaining power of all battery packs in the energy storage system is less than a third preset difference, and then proceeding to step S34; S34: Re-power on all battery packs in order from low to high voltage.

[0010] Step S3 can effectively balance the power between battery packs by accurately managing the power differences of each battery pack in the energy storage system, thereby extending the service life of the battery pack and preventing the battery from degrading due to overcharging or over-discharging. This step balances the power differences of each battery pack in the energy storage system through intelligent scheduling and charging strategy optimization, improves system stability, extends battery life, and ensures efficient operation.

[0011] Furthermore, the step S4 includes: if the number of parallel battery packs is greater than or equal to 2, only the battery packs whose remaining power voltage difference with the battery pack with the maximum remaining power in the energy storage system is less than a second preset difference are allowed to be powered on, and the battery packs are powered on in descending order of voltage.

[0012] Furthermore, the step S4 includes: if the required number of parallel machines is less than 2, and the remaining power of all battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both less than a first preset difference, then the batteries are put online in a descending order of voltage; if the required number of parallel machines is less than 2, and the remaining power of the battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both greater than a third preset difference, then only the battery pack with the highest voltage is powered on, and after the remaining power of all battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both less than the first preset difference, then the batteries are put online in a descending order of voltage.

[0013] This step ensures the reasonable selection of battery packs to go online under parallel conditions by setting the remaining power voltage difference and voltage sequence, optimizing battery power distribution and system stability, and avoiding system failure or battery damage caused by unbalanced power differences. Through the above measures, the system can adopt different power-on strategies under different battery pack power differences, avoiding the impact of unbalanced power between battery packs on the performance of the energy storage system, ensuring efficient and stable operation of the system, avoiding damage and extending the battery life.

[0014] Furthermore, steps S3 and S4 also include: if the reverse current of the battery pack in the energy storage system is greater than the first preset current, the synchronous rectification MOS tube of the LLC of the battery pack is turned off, until the reverse current is restored to the forward current and is greater than the second preset current, and then the synchronous rectification MOS tube is turned on again.

[0015] When reverse current flows into the battery pack, it may damage the battery, especially have an adverse effect on the charge and discharge cycle and life of the battery. When the reverse current of the battery pack exceeds the first preset current, the reverse current flow can be effectively blocked by turning off the synchronous rectification MOS tube to prevent the battery from being damaged by the reverse current.

[0016] By controlling the opening and closing of the synchronous rectifier MOS tube, the system can effectively manage the reverse current in the battery pack, avoid battery damage, improve the safety and stability of the system, and optimize the efficiency of the charging and discharging process. This control method helps to improve the overall performance of the energy storage system, extend battery life, and ensure that the system can maintain efficient operation under various working conditions.

[0017] Furthermore, if there is a fully charged battery pack at the charging end, the fully charged battery pack is powered off.

[0018] Furthermore, if an overcurrent fault occurs in the battery pack at the end of discharge, the LLC of the corresponding battery pack is shut down.

[0019] Furthermore, if a battery pack has a minor fault, the energy output of the battery pack is limited; if a battery pack has a major fault, the battery pack is powered off separately.

[0020] Furthermore, if the faulty battery pack is repaired or a new battery pack is added, it is powered on and charged and discharged according to step S3 or S4.

[0021] When there is a fully charged battery pack at the end of the charge, disconnecting the battery pack helps prevent overcharging. Overcharging not only affects the battery life, but may also cause battery heating, swelling, or safety accidents. By disconnecting the fully charged battery pack in time, you can ensure that the battery system is in a safe charging state and avoid energy waste.

[0022] When a battery pack overcurrent fault occurs at the end of discharge, the LLC (load-to-battery converter) of the corresponding battery pack is turned off to prevent overcurrent from damaging the battery system. Overcurrent faults may cause battery overheating, damage, or even fire, so disconnecting the faulty battery pack in time can effectively avoid safety risks.

[0023] For a faulty battery pack, its energy output is limited in the case of a minor fault, and it is directly powered off in the case of a major fault. This strategy can provide targeted responses based on the severity of the fault: for a minor fault, the battery pack can still be used to perform some work; for a major fault, it is necessary to completely power off to prevent the fault from spreading.

[0024] When the faulty battery pack is repaired or a new battery pack is added, it can be rescheduled to be powered on and participate in charging and discharging according to the steps of step S3 or S4. This means that once the battery pack is restored to normal or a new battery pack is added, the system will manage it according to its current status to ensure that it can be put into use safely and effectively.

[0025] In a second aspect, the present application proposes a computer-readable storage medium, which stores computer-executable instructions, characterized in that when the computer-executable instructions are executed by a control processor, the parallel connection method of a multi-LLC parallel energy storage system as described in the first aspect is implemented.

[0026] In summary, the present application proposes a method for parallel connection of multiple LLC parallel energy storage systems, wherein the energy storage system includes multiple battery packs with built-in LLCs. The method for parallel connection of multiple LLC parallel energy storage systems determines whether the battery pack voltage is normal and checks the connection status to ensure that the system is in the correct state, and then performs different operations according to the operating state of the energy storage system: in standby state, wait for charging or discharging instructions; in charging state, balance the battery pack power and re-power on all of them in order from low to high; in discharging state, determine the number of parallel battery packs based on the required power, and power on them in order from high to low voltage.

[0027] Compared with the prior art, this application has at least the following beneficial effects: The present invention solves the problem of capacity differences between different battery packs, avoids the situation where battery packs cannot be used at the same time, effectively prevents the battery circulation problem caused by capacity mismatch, and ensures the stability of battery packs when they are connected in parallel. By optimizing energy distribution, the overall performance of the system is improved, allowing the energy storage system to operate more efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of a method for parallel connection of a multi-LLC parallel energy storage system shown in an embodiment of the present application.

[0029] Figure 2 This is the energy storage system shown in the embodiment of the present application.

[0030] Figure 3 This is a battery pack parallel power-up flow chart shown in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] Embodiment 1: As attached Figure 1 As shown, the present application proposes a parallel connection method for a multi-LLC energy storage system, wherein the energy storage system includes a plurality of battery packs with built-in LLCs, and the parallel connection method for the energy storage system specifically includes: S1: Determine whether the voltage of each battery pack in the energy storage system is within a normal range. If so, proceed to step S2; otherwise, check the connection status of the battery pack and execute step S1 again; S2: Obtain the current operating status of the energy storage system. If the energy storage system is in a standby state, wait for a charge and discharge instruction; if the energy storage system is in a charging state, proceed to step S3; if the energy storage system is in a discharging state, proceed to step S4; S3: Obtain the remaining power of all battery packs in the energy storage system, calculate the difference in remaining power between all battery packs in the energy storage system, perform strategy processing according to the maximum difference in remaining power, until the difference in remaining power between all battery packs in the energy storage system is less than a preset difference, and then re-power on all battery packs in order from low to high voltage; S4: Obtain the power demand of the device, determine the number of battery packs that need to be connected in parallel according to the power demand, and then power on the battery packs in descending order of voltage.

[0033] This application effectively avoids system failures caused by abnormal battery packs by judging in real time whether the voltage of each battery pack is within the normal range, and checking and retrying when the voltage is abnormal. This can ensure the stability of the entire energy storage system and avoid potential safety hazards. In the charging state, the system automatically obtains the remaining power of all battery packs and performs balanced charging to ensure that the power of all battery packs is balanced. This charging strategy helps to extend the service life of the battery pack and avoid excessive discharge or overcharging caused by uneven battery power, thereby improving the efficiency and safety of the system; in the discharge state, the system automatically determines the number of battery packs that need to be connected in parallel according to the required power of the equipment, and powers on the battery packs in order from high to low voltage, thereby ensuring the flexible response of the system under different load requirements, optimizing the use efficiency of the battery pack, and ensuring the stability of power supply. The system gives priority to starting the battery pack with higher voltage according to the voltage difference of the battery pack, and reasonably allocates energy storage resources, thereby achieving efficient and uniform battery pack paralleling. This paralleling method can meet different power requirements while avoiding over-reliance on certain battery packs, improving the overall operating efficiency and stability of the system.

[0034] As a preferred embodiment, Figure 2As shown, it is a specific energy storage system structure diagram, the energy storage system includes multiple battery packs, inverters and processing modules; the processing module includes: the positive interface of the inverter is connected to the positive electrode of the inverter, and the negative interface of the inverter is connected to the negative electrode of the inverter; one end of the Input EMI is connected to the positive interface of the inverter and the negative interface of the inverter, and the other end is connected to the Soft-start; the other end of the Soft-start is connected to the DCDC module; the other end of the DCDC module is connected to the EMI; the EMI is connected to two bus bars and connected to the wiring harness parallel structure of the subsequent battery pack. The battery pack includes: the positive electrode of the battery pack is connected to the sub-DCDC module through a fuse, and the negative electrode of the battery pack is connected to the sub-DCDC module; the sub-DCDC module is connected to the sub-Soft-start; the sub-Soft-start is connected to the sub-EMI; the sub-EMI is connected to the wiring harness parallel structure; the wiring harness parallel structure is connected to the wiring harness parallel structure of the subsequent battery pack through two bus bars.

[0035] In the embodiment of the present invention, optionally, step S3 includes: S31: Determine the difference in remaining power among all battery packs in the energy storage system. If the maximum remaining power difference is less than the first preset difference, proceed to step S34. If the maximum remaining power difference is greater than the first preset difference, charge the battery pack with the smallest remaining power and proceed to step S32. S32: when the remaining power of the battery pack currently being charged is the largest among all the battery packs, determining the maximum difference in the remaining power among all the battery packs in the energy storage system, and if the current maximum difference in the remaining power is greater than a second preset difference, powering off the battery pack currently being charged, and powering on the battery pack with the smallest remaining power for charging; S33: repeating step S32 until the difference in the remaining power of all battery packs in the energy storage system is less than a third preset difference, and then proceeding to step S34; S34: Re-power on all battery packs in order from low to high voltage.

[0036] Step S3 can effectively balance the power between battery packs by accurately managing the power differences of each battery pack in the energy storage system, thereby extending the service life of the battery pack and preventing the battery from degrading due to overcharging or over-discharging. This step balances the power differences of each battery pack in the energy storage system through intelligent scheduling and charging strategy optimization, improves system stability, extends battery life, and ensures efficient operation.

[0037] In an embodiment of the present invention, optionally, step S4 includes: if the number of parallel battery packs is greater than or equal to 2, only the battery packs whose remaining power voltage difference with the battery pack with the maximum remaining power in the energy storage system is less than a second preset difference are allowed to be powered on, and the battery packs are powered on in order of voltage from high to low.

[0038] In an embodiment of the present invention, optionally, step S4 includes: if the required number of parallel machines is less than 2, and the remaining power of all battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both less than a third preset difference, then the batteries are put online in descending order of voltage; if the required number of parallel machines is less than 2, and the remaining power of the battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both greater than a third preset difference, then only the battery pack with the highest voltage is powered on, and after the remaining power of all battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both less than the third preset difference, then the batteries are put online in descending order of voltage.

[0039] This step ensures the reasonable selection of battery packs to go online under parallel conditions by setting the remaining power voltage difference and voltage sequence, optimizing battery power distribution and system stability, and avoiding system failure or battery damage caused by unbalanced power differences. Through the above measures, the system can adopt different power-on strategies under different battery pack power differences, avoiding the impact of unbalanced power between battery packs on the performance of the energy storage system, ensuring efficient and stable operation of the system, avoiding damage and extending the battery life.

[0040] As a preferred embodiment, Figure 3 The figure shows the battery pack parallel power-up flow chart.

[0041] As a preferred embodiment, it is assumed that there are five battery packs (i.e., battery packs A, B, C, D, and E) in the energy storage system, and the following preset differences are set: First preset difference: 30% Second preset difference: 20% Third preset difference: 10% Scenario 1: The difference in remaining power among the five battery packs is less than 30%.

[0042] Step S31: First, determine the difference in remaining power between the battery packs. If the maximum difference in remaining power between each battery pack is less than 30%, skip the charging operation and directly enter step S34 to re-power the battery packs in order of voltage from low to high.

[0043] For example, assuming that the remaining power of battery pack A is 90%, B is 88%, C is 85%, D is 86%, and E is 87%. At this time, the maximum remaining power difference is 5%, which is less than the first preset difference of 30%. Therefore, step S34 is directly entered to re-power on in voltage order.

[0044] In this scenario, the system can effectively maintain a small difference in charge between battery packs, avoid unnecessary charging operations, reduce energy waste, and optimize battery management.

[0045] Scenario 2: The difference in remaining power among the five battery packs is greater than 30% Step S31: Determine the difference in remaining power between the battery packs. If the maximum remaining power difference is greater than 30%, select the battery pack with the smallest remaining power for charging.

[0046] For example, assuming that the remaining power of battery pack A is 50%, B is 55%, C is 60%, D is 70%, and E is 90%. At this time, the maximum remaining power difference is 40% (90%-50%), which is greater than the first preset difference of 30%.

[0047] Step S32: Charge battery pack A (the battery pack with the smallest remaining power) until its remaining power is close to the level of other battery packs. At this time, it is necessary to continuously monitor the remaining power of the battery packs to determine whether further charging is required.

[0048] During the charging process, the remaining power of battery pack A may gradually increase. The system continuously monitors the power changes of each battery pack. If the power difference of some battery packs is still large (such as more than 20%) after charging, the system will continue to adjust.

[0049] Step S33: If the difference in remaining power between the charged battery packs is greater than 20%, the charging operation continues. Assume that battery pack A is charged to 60%, and battery packs B, C, D, and E are charged to 65%, 70%, 75%, and 90% respectively, with a maximum power difference of 30%. At this point, the battery packs are still quite different, and the system will make further adjustments.

[0050] The system will determine the difference in remaining power between the battery packs and determine whether to switch the battery pack to be charged based on the second preset difference (20%). If necessary, the system will power off the currently charged battery pack (e.g., battery pack A) and recharge the battery pack with the smallest remaining power until the difference is further reduced.

[0051] Step S33 continues: After multiple adjustments and charging, the power differences of the battery packs gradually decrease until the remaining power differences of all battery packs are less than 10% (the third preset difference), and then enters step S34.

[0052] Dynamic adjustment during charging: During the charging process, the difference in the remaining power of the battery packs will change in real time. For example, if at a certain stage the remaining power of battery pack A is too high (reaching 80%), while the remaining power of battery pack B is only 40%, the system may immediately adjust the charging strategy and select the next battery pack with the smallest power (such as B) for charging to ensure that the power difference between the battery packs gradually approaches.

[0053] During this process, the system will monitor and adjust the charging strategy in real time, and ensure that the power difference between battery packs continues to decrease through precise power management, eventually reaching a balanced state.

[0054] Assuming that the power difference between the battery packs is small enough and the power difference of each battery pack is less than 10%, the system will directly enter step S34 and repower the battery packs in order from low to high voltage to ensure smooth operation of the system.

[0055] As a preferred embodiment, it is assumed that there are five battery packs (i.e., battery packs A, B, C, D, and E) in the energy storage system, and the following preset differences are set: First preset difference: 30% Second preset difference: 20% Third preset difference: 10% When the number of parallel battery packs is greater than or equal to 2, the system only allows the battery pack whose voltage difference between the remaining power and the maximum remaining power is less than the second preset difference to be powered on. This can avoid excessive power differences between battery packs, thereby reducing performance degradation or damage caused by power imbalance.

[0056] The system first calculates the power difference between the battery packs to ensure that the voltage difference between the remaining power and the maximum remaining power is less than the second preset difference (20%).

[0057] Assumptions: Battery Pack A: 70% Battery Pack B: 65% Battery Pack C: 55% Battery Pack D: 85% Battery Pack E: 75% The system determines that the maximum power difference between battery packs is 30% (85%-55%). Since the power of battery pack C is more than 30% lower than that of other battery packs, this battery pack will not go online at this time.

[0058] When the number of parallel battery packs is ≥ 2, the system only allows battery packs with a difference between the remaining power and the maximum remaining power of less than 20% to go online, and the power-on sequence follows the order of voltage from high to low.

[0059] Assume that the battery pack voltages are ranked as follows: D>E>A>B>C (battery pack D has the highest voltage).

[0060] Battery pack D, as the battery pack with the highest voltage, will be put online first. Under the premise of ensuring that the power difference is less than 20%, the subsequent battery packs will be put online in order of voltage.

[0061] Scenario 2: When the number of parallel battery packs is less than 2 When the number of parallel battery packs is less than 2 and the power difference between all battery packs and the battery pack with the largest remaining power is less than 30%, the system will power on in descending order of battery voltage.

[0062] Assume that only one battery pack is online at this time, and the power difference between the other battery packs and it is less than 10%.

[0063] For example, the power level of battery pack A is 80%, and the power levels of other battery packs are: B (75%), C (70%), D (82%), and E (78%). The maximum power difference is 10%, which is less than the first preset difference.

[0064] The system will start the battery packs in the order of their voltages (high to low) while ensuring that the power difference is less than 10%.

[0065] Assuming that the battery pack voltage is sorted as: D>E>A>B>C, battery pack D will be put online first, and then gradually put online in the order of voltage sorting.

[0066] When the number of parallel battery packs is small, the system can still maintain the balance of battery pack power, avoiding the problem of power imbalance during the charging process, and also preventing excessive battery voltage differences from affecting charging efficiency.

[0067] Scenario 3: The battery pack power difference is greater than the third preset difference When the power difference between battery packs is large (exceeding the third preset difference (10%)), the system only allows the battery pack with the highest voltage to go online. After the power difference is reduced to below the first preset difference, other battery packs are gradually put online in order of battery voltage.

[0068] Assume that battery pack A: 50%, B: 60%, C: 40%, D: 85%, E: 70%, then the maximum power difference is 45% (85%-40%), which is greater than the third preset difference (10%).

[0069] Since the power difference is too large, the system will only allow the battery pack with the highest voltage (ie, battery pack D) to go online until the power difference between the battery packs is reduced to below the first preset difference (30%).

[0070] After battery pack D goes online, the system will gradually monitor the battery pack power differences. If the difference is narrowed to within 10%, battery packs E, A, B and C can be gradually put online.

[0071] In the embodiment of the present invention, the preset difference is optionally used to prevent the circulation phenomenon between battery packs. Circulation refers to the unnecessary current flow between multiple parallel battery packs when the power difference is large. This phenomenon not only wastes energy, but also may cause increased battery loss and even cause safety problems such as battery thermal runaway.

[0072] Specifically, the preset difference is to control the power difference between battery packs by setting a power difference threshold, thereby avoiding circulation. Setting an appropriate preset difference has the following key functions: When the power difference between battery packs is too large, circulation may occur between batteries. Circulation not only makes the charging process unbalanced, but also may cause heat accumulation due to excessive current flow, further affecting the battery life. By presetting the difference, the system will only allow the battery packs to work in parallel when the battery power difference is within the allowable range, thus avoiding circulation.

[0073] In an embodiment of the present invention, optionally, steps S3 and S4 further include: if the reverse current of the battery pack in the energy storage system is greater than a first preset current, the synchronous rectification MOS tube of the LLC of the battery pack is turned off, until the reverse current is restored to a forward current and is greater than a second preset current, and then the synchronous rectification MOS tube is turned on again.

[0074] When reverse current flows into the battery pack, it may damage the battery, especially have an adverse effect on the charge and discharge cycle and life of the battery. When the reverse current of the battery pack exceeds the first preset current, the reverse current flow can be effectively blocked by turning off the synchronous rectification MOS tube to prevent the battery from being damaged by the reverse current.

[0075] By controlling the opening and closing of the synchronous rectifier MOS tube, the system can effectively manage the reverse current in the battery pack, avoid battery damage, improve the safety and stability of the system, and optimize the efficiency of the charging and discharging process. This control method helps to improve the overall performance of the energy storage system, extend battery life, and ensure that the system can maintain efficient operation under various working conditions.

[0076] In the embodiment of the present invention, optionally, if there is a fully charged battery pack at the charging terminal, the fully charged battery pack is powered off.

[0077] In an embodiment of the present invention, optionally, if a battery pack overcurrent fault occurs at the end of discharge, the LLC of the corresponding battery pack is turned off.

[0078] In the embodiment of the present invention, optionally, if a battery pack has a minor fault, the energy output of the battery pack is limited; if a battery pack has a major fault, the battery pack is powered off separately.

[0079] In the embodiment of the present invention, optionally, if the faulty battery pack is repaired or a new battery pack is added, it is powered on and arranged to participate in charging and discharging according to step S3 or S4.

[0080] When there is a fully charged battery pack at the end of the charge, disconnecting the battery pack helps prevent overcharging. Overcharging not only affects the battery life, but may also cause battery heating, swelling, or safety accidents. By disconnecting the fully charged battery pack in time, you can ensure that the battery system is in a safe charging state and avoid energy waste.

[0081] When a battery pack overcurrent fault occurs at the end of discharge, the LLC (load-to-battery converter) of the corresponding battery pack is turned off to prevent overcurrent from damaging the battery system. Overcurrent faults may cause battery overheating, damage, or even fire, so disconnecting the faulty battery pack in time can effectively avoid safety risks.

[0082] For a faulty battery pack, its energy output is limited in the case of a minor fault, and it is directly powered off in the case of a major fault. This strategy can provide targeted responses based on the severity of the fault: for a minor fault, the battery pack can still be used to perform some work; for a major fault, it is necessary to completely power off to prevent the fault from spreading.

[0083] When the faulty battery pack is repaired or a new battery pack is added, it can be rescheduled to be powered on and participate in charging and discharging according to the steps of step S3 or S4. This means that once the battery pack is restored to normal or a new battery pack is added, the system will manage it according to its current status to ensure that it can be put into use safely and effectively.

[0084] Embodiment 2: The present application proposes a computer-readable storage medium, which stores computer-executable instructions, characterized in that when the computer-executable instructions are executed by a control processor, a parallel connection method for a multi-LLC parallel energy storage system as described in Example 1 is implemented.

[0085] In summary, the present application proposes a method for parallel connection of multiple LLC parallel energy storage systems, wherein the energy storage system includes multiple battery packs with built-in LLCs. The method for parallel connection of multiple LLC parallel energy storage systems determines whether the battery pack voltage is normal and checks the connection status to ensure that the system is in the correct state, and then performs different operations according to the operating state of the energy storage system: in standby state, wait for charging or discharging instructions; in charging state, balance the battery pack power and re-power on all of them in order from low to high; in discharging state, determine the number of parallel battery packs based on the required power, and power on them in order from high to low voltage.

[0086] The present invention solves the problem of capacity differences between different battery packs, avoids the situation where battery packs cannot be used at the same time, effectively prevents the battery circulation problem caused by capacity mismatch, and ensures the stability of battery packs when they are connected in parallel. By optimizing energy distribution, the overall performance of the system is improved, allowing the energy storage system to operate more efficiently.

[0087] In several embodiments provided in the present application, it is understood that each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved.

[0088] If the function is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can essentially or in other words, the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for an electronic device to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program code.

[0089] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the scope of protection of the present application. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for parallel connection of multiple LLC energy storage systems, characterized in that: The energy storage system includes a plurality of battery packs with built-in LLCs, and the energy storage system parallel connection method specifically includes: S1: Determine whether the voltage of each battery pack in the energy storage system is within a normal range. If so, proceed to step S2. Otherwise, check the connection status of the battery pack and execute step S1 again. S2: Obtain the current operating status of the energy storage system. If the energy storage system is in a standby state, wait for a charge and discharge instruction; if the energy storage system is in a charging state, proceed to step S3; if the energy storage system is in a discharging state, proceed to step S4; S3: Obtain the remaining power of all battery packs in the energy storage system, calculate the difference in remaining power between all battery packs in the energy storage system, perform strategy processing according to the maximum difference in remaining power, until the difference in remaining power between all battery packs in the energy storage system is less than a preset difference, and then re-power on all battery packs in order from low to high voltage; S4: Obtain the power demand of the device, determine the number of battery packs that need to be connected in parallel according to the power demand, and then power on the battery packs in descending order of voltage.

2. The method for parallel connection of multiple LLC energy storage systems according to claim 1, characterized in that: The step S3 comprises: S31: Determine the difference in remaining power among all battery packs in the energy storage system. If the maximum remaining power difference is less than the first preset difference, proceed to step S34. If the maximum remaining power difference is greater than the first preset difference, charge the battery pack with the smallest remaining power and proceed to step S32. S32: when the remaining power of the battery pack currently being charged is the largest among all the battery packs, determining the maximum difference in the remaining power among all the battery packs in the energy storage system, and if the current maximum difference in the remaining power is greater than a second preset difference, powering off the battery pack currently being charged, and powering on the battery pack with the smallest remaining power for charging; S33: repeating step S32 until the difference in the remaining power of all battery packs in the energy storage system is less than a third preset difference, and then proceeding to step S34; S34: Re-power on all battery packs in order from low to high voltage.

3. The method for parallel connection of multiple LLC energy storage systems according to claim 2, characterized in that: If there is a fully charged battery pack at the charging end, the fully charged battery pack is powered off.

4. The method for parallel connection of multiple LLC energy storage systems according to claim 1, characterized in that: The step S4 includes: if the number of parallel battery packs is greater than or equal to 2, only the battery pack whose remaining power voltage difference with the battery pack with the largest remaining power in the energy storage system is less than a second preset difference is allowed to power on, and the battery packs are powered on in descending order of voltage.

5. The method for parallel connection of multiple LLC energy storage systems according to claim 1, characterized in that: The step S4 also includes: if the required number of parallel machines is less than 2, and the remaining power of all battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both less than a first preset difference, then the batteries are put online in a descending order of voltage; if the required number of parallel machines is less than 2, and the remaining power of the battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both greater than a third preset difference, then only the battery pack with the highest voltage is powered on, and after the remaining power of all battery packs in the energy storage system and the remaining power voltage difference between the battery pack with the largest remaining power in the energy storage system are both less than the first preset difference, then the batteries are put online in a descending order of voltage.

6. The method for parallel connection of multiple LLC energy storage systems according to any one of claims 2 to 5, characterized in that: If the reverse current of the battery pack in the energy storage system is greater than the first preset current, the synchronous rectification MOS tube of the LLC of the battery pack is turned off until the reverse current returns to the forward current and is greater than the second preset current, and then the synchronous rectification MOS tube is turned on again.

7. The method for parallel connection of multiple LLC energy storage systems according to claim 6, characterized in that: If a battery pack overcurrent fault occurs at the end of discharge, the LLC of the corresponding battery pack will be shut down.

8. The method for parallel connection of multiple LLC energy storage systems according to claim 6, characterized in that: If a battery pack has a minor fault, the energy output of the battery pack will be limited; if a battery pack has a major fault, the battery pack will be powered off separately.

9. The method for parallel connection of multiple LLC energy storage systems according to claim 8, characterized in that: If the faulty battery pack is repaired or a new battery pack is added, charging and discharging are performed according to step S3 or S4.

10. A computer-readable storage medium storing computer-executable instructions, characterized in that: When the computer executable instructions are executed by the control processor, the parallel connection method of the energy storage system with multiple LLCs in parallel is implemented as described in any one of claims 1 to 9.

Images