Battery equalization system and control method thereof, vehicle and medium

Abstract

The application discloses a battery equalization system and a control method thereof, a vehicle and a medium, and relates to the technical field of battery equalization. In the application, state information of a target battery module is acquired, and the aging degree of the target battery module is determined based on the state information; a first state of charge threshold of the target battery module is calculated based on the aging degree and a preset coefficient; in response to a difference between the state of charge of a target battery cell and the average state of charge of the target battery module being greater than the first state of charge threshold, a target active equalization unit is determined based on the number of the target battery cell, and a first control parameter of the target active equalization unit is determined; and the target active equalization unit is controlled based on the first control parameter to equalize the state of charge of the target battery module. In this way, the battery aging degree is dynamically introduced into the equalization judgment basis, so that the equalization strategy can be adaptively adjusted according to the battery aging state, and the energy management accuracy and consistency can be maintained at a high level throughout the whole life cycle of the battery module.

Description

Technical Field

[0001] This application relates to the field of battery balancing technology, and in particular to a battery balancing system and its control method, vehicle and medium. Background Technology

[0002] In actual battery pack applications, the inconsistency of individual cells due to manufacturing process variations and differences in operating environments is becoming increasingly prominent, making battery balancing technology a key element in ensuring system performance and safety.

[0003] Currently, most BMS (Battery Management Systems) employ a voltage-based passive balancing strategy, using balancing resistors to dissipate excess energy from high-voltage cells as heat. While this method is structurally simple, it is limited by the small balancing current, long balancing time, and overall low energy efficiency. More importantly, as the number of cycles increases, the differences in SOH (State of Health) among individual cells gradually widen, manifesting as varying degrees of capacity decay and internal resistance increase. Even if the SOC (State of Charge) of each cell appears consistent, the actual energy and power output of low-SOH aged cells are significantly lower than that of healthy cells, leading to a prominent contradiction between apparent consistency and actual imbalance. Therefore, it is urgent to incorporate SOH information into the balancing strategy for comprehensive judgment.

[0004] To address the aforementioned needs, related technologies use the product of SOH and SOC as the balancing coefficient to balance the battery. This method is essentially a linear product mapping and fails to delve into the nonlinear impact of SOH degradation on balancing requirements under different SOC ranges and operating conditions. The balancing decision remains relatively coarse and it is difficult to achieve refined and adaptive energy redistribution in complex aging scenarios. Summary of the Invention

[0005] One objective of this invention is to provide a control method for a battery balancing system to solve the problem in related technologies that fail to reflect the nonlinear effects of SOH degradation under different SOC ranges and operating conditions, resulting in coarse balancing decisions and difficulty in achieving refined adaptive energy redistribution; a second objective is to provide a battery balancing system; a third objective is to provide a computer-readable storage medium; and a fourth objective is to provide a vehicle.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A control method for a battery balancing system, the system comprising a target battery module and an active balancing module, the target battery module comprising multiple target battery cells connected in series, the active balancing module comprising multiple active balancing units, a first end of an active balancing unit connected to a corresponding target battery cell node, the target battery cell node being used to characterize the connection node between adjacent target battery cells, and a second and third end of an active balancing unit connected to the first and second ends of the target battery module, respectively; the method comprising: acquiring state information of the target battery module and determining the aging degree of the target battery module based on the state information; calculating a first state of charge threshold of the target battery module based on the aging degree and a preset coefficient; responding to a difference between the state of charge of the target battery cells and the average state of charge of the target battery module being greater than the first state of charge threshold, determining a target active balancing unit based on the number of the target battery cells, and determining a first control parameter of the target active balancing unit; and controlling the target active balancing unit based on the first control parameter to perform state of charge balancing on the target battery module.

[0007] According to one embodiment of this application, the active balancing unit includes an inductor and an inductor direction switching unit. The first end of the inductor is connected to the corresponding target battery cell node, the second end of the inductor is connected to the first end of the corresponding inductor direction switching unit, and the second and third ends of the inductor direction switching unit are respectively connected to the first and second ends of the target battery module.

[0008] According to one embodiment of this application, the inductor direction switching unit includes a first switch and a second switch. The first end of the first switch is connected to the first end of the target battery module, and the second end of the second switch is connected to the second end of the target battery module. The connection node between the second end of the first switch and the first end of the second switch is connected to the second end of the inductor. The first control parameters include a first conduction duration of the first switch and a second conduction duration of the second switch. Determining the first control parameters of the target active balancing unit includes: calculating the first conduction duration and the second conduction duration based on the target battery cell number, the number of target battery cells in the target battery module, and a preset closing period. Controlling the target active balancing unit based on the first control parameters includes: controlling the first switch and the second switch corresponding to the target active balancing unit based on a preset conduction sequence, the first conduction duration, and the second conduction duration.

[0009] According to one embodiment of this application, the system further includes a passive balancing module, which includes multiple passive balancing units. Each passive balancing unit corresponds to a target battery cell, and the passive balancing unit is connected in parallel with the corresponding target battery cell. The method includes: in response to a difference value being less than or equal to a first state of charge threshold and greater than a second state of charge threshold, determining a second control parameter for the passive balancing unit corresponding to the target battery cell; and controlling the passive balancing unit corresponding to the target battery cell based on the second control parameter to perform state of charge balancing on the target battery module.

[0010] According to one embodiment of this application, the passive equalization unit includes a resistor and a third switch, with the resistor and the third switch connected in series; wherein, the second control parameter includes the third closing time of the third switch, and determining the second control parameter of the passive equalization unit corresponding to the target battery cell includes: calculating the third closing time based on the difference and the resistance; wherein, controlling the passive equalization unit corresponding to the target battery cell based on the second control parameter includes: controlling the third switch based on the third closing time.

[0011] According to one embodiment of this application, the method further includes: controlling the first switch, the second switch and the third switch to be in an off state in response to the difference being less than or equal to a second state of charge threshold.

[0012] According to one embodiment of this application, the preset coefficients are generated as follows: A search interval, search step size, and convergence accuracy for the first state of charge (SOC) thresholds of multiple test battery modules are determined, wherein the aging degree of each test battery module is different; based on the upper and lower boundaries of the search interval and the search step size, a first candidate SOC threshold and a second candidate SOC threshold for the test battery modules are determined; based on the first and second candidate SOC thresholds, SOC balancing processing is performed on the test battery modules respectively, and performance scores corresponding to the first and second candidate SOC thresholds are calculated based on the balancing processing results; the search interval is updated based on the performance scores, and the first and second candidate SOC thresholds are re-determined based on the updated search interval until the absolute value of the difference between the first and second candidate SOC thresholds is less than the convergence accuracy, and the average of the first and second candidate SOC thresholds is determined as the first SOC threshold of the test battery module; the aging degree of the multiple test battery modules and the corresponding first SOC thresholds are fitted to obtain the preset coefficients.

[0013] According to one embodiment of this application, the performance score of the first candidate state of charge threshold and the second candidate state of charge threshold is calculated based on the equalization processing result, including: parsing the equalization processing result to obtain the first remaining cycle life of the test battery module and the first state of charge standard deviation of the test battery cells of the test battery module; obtaining the second remaining cycle life of the test battery module and the second state of charge standard deviation of the test battery cells of the test battery module; calculating the life improvement rate of the test battery module based on the first remaining cycle life and the second remaining cycle life; calculating the consistency improvement rate of the test battery module based on the first state of charge standard deviation and the second state of charge standard deviation; and calculating the performance score of the first candidate state of charge threshold and the second candidate state of charge threshold based on the life improvement rate and the consistency improvement rate.

[0014] According to one embodiment of this application, updating the search interval based on the performance score includes: updating the first candidate state of charge threshold as the lower boundary of the search interval in response to the performance score corresponding to the first candidate state of charge threshold being greater than the performance score corresponding to the second candidate state of charge threshold; and updating the first candidate state of charge threshold as the upper boundary of the search interval in response to the performance score corresponding to the second candidate state of charge threshold being greater than the performance score corresponding to the first candidate state of charge threshold.

[0015] A battery balancing system includes: a target battery module, an active balancing module, and a controller. The target battery module includes multiple target battery cells connected in series. The active balancing module includes multiple active balancing units. A first end of an active balancing unit is connected to a corresponding target battery cell node, whereby the target battery cell node represents the connection node between adjacent target battery cells. A second end and a third end of the active balancing unit are connected to the first end and the second end of the target battery module, respectively. The controller is used to acquire state information of the target battery module and calculate the aging degree of the target battery module based on the state information. Based on the aging degree and a preset coefficient, a first state of charge threshold is calculated. In response to a situation where the difference between the state of charge of a target battery cell and the average state of charge of the target battery module is greater than the first state of charge threshold, a target active balancing unit is determined based on the number of the target battery cell, and a first control parameter of the target active balancing unit is determined. The controller then controls the target active balancing unit based on the first control parameter to perform state of charge balancing on the target battery module.

[0016] A computer-readable storage medium storing a battery balancing program thereon, which, when executed by a processor, implements the aforementioned control method for a battery balancing system.

[0017] A vehicle includes a memory, a processor, and a battery balancing program stored in the memory and capable of running on the processor. When the processor executes the battery balancing program, it implements a control method according to the aforementioned battery balancing system.

[0018] The beneficial effects of this invention are as follows: This application obtains the state information of the target battery module and determines its aging degree. Based on the aging degree and a preset coefficient, a first state of charge (SOH) threshold adapted to the current aging state is calculated. This threshold is then used to determine the deviation between the SOC of each battery cell and the average value of the module, thereby triggering active balancing control. In this way, the battery aging degree is dynamically introduced into the balancing judgment criteria, solving the problems in related technologies that fail to reflect the nonlinear effects of SOH degradation under different SOC ranges and operating conditions, leading to coarse balancing decisions and difficulty in achieving refined adaptive energy redistribution. This allows the balancing strategy to adaptively adjust with the battery aging state, maintaining high energy management accuracy and consistency throughout the entire life cycle of the battery module. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a battery balancing system according to some embodiments of this application; Figure 2 This is a flowchart illustrating a control method for a battery balancing system according to some embodiments of this application; Figure 3 This is a schematic diagram of the structure of an active equalization unit according to some embodiments of this application; Figure 4 This is a schematic diagram of the structure of an inductor direction switching unit according to some embodiments of this application; Figure 5 This is a schematic diagram of the structure of a battery balancing system according to other embodiments of this application; Figure 6 This is a schematic diagram of the structure of a battery balancing system according to some embodiments of this application; Figure 7 This is a schematic diagram of the structure of a passive equalization unit according to some embodiments of this application; Figure 8 This is a flowchart illustrating a control method for a battery balancing system according to other embodiments of this application; Figure 9(a1) is a schematic diagram of the structure of a battery balancing system according to some embodiments of this application; Figure 9(a2) is a pulse signal timing diagram according to some embodiments of this application; Figure 10(b1) is a schematic diagram of the structure of a battery balancing system according to some embodiments of this application; Figure 10(b2) is a pulse signal timing diagram according to some other embodiments of this application; Figure 11This is a schematic diagram of passive equalization simulation results according to some embodiments of this application; Figure 12 This is a schematic diagram of active equalization simulation results according to some embodiments of this application; Figure 13 This is a block diagram of a vehicle according to some embodiments of this application. Detailed Implementation

[0020] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0021] The following describes in detail, with reference to the accompanying drawings, the battery balancing system and its control method, vehicle and medium according to embodiments of this application.

[0022] Reference Figure 1 The battery balancing system of this application embodiment includes a target battery module and an active balancing module. The target battery module includes multiple target battery cells connected in series. The active balancing module includes multiple active balancing units. The first end of the active balancing unit is connected to the corresponding target battery cell node. The target battery cell node is used to characterize the connection node between adjacent target battery cells. The second and third ends of the active balancing unit are connected to the first and second ends of the target battery module, respectively. For example, the first end of the active balancing unit Z1 is connected to the corresponding target battery cell node (the node between target battery cell BT1 and target battery cell BT2). The second and third ends of the active balancing unit Z1 are connected to the first end (positive terminal of BT1) and the second end (negative terminal of BT2) of the target battery module 11, respectively.

[0023] It should be noted that the first end of the active balancing unit is connected to the corresponding target battery cell node. Therefore, the number of active balancing units is one less than the number of target battery cells. For example, if the target battery module includes n target battery cells connected in series, then the number of active balancing units is n-1.

[0024] Figure 2 This is a flowchart of a control method for a battery balancing system according to some embodiments of this application. (Refer to...) Figure 2 The control method of the battery balancing system in this application embodiment may include the following steps: S110: Obtain the status information of the target battery module and determine the aging degree of the target battery module based on the status information.

[0025] Specifically, the status information of the target battery module includes its current, voltage, and temperature. The current of the target battery module can be acquired by a current sensor installed in the main charging / discharging circuit of the target battery module; the current of the target battery module can be acquired by a voltage sensor installed in the main charging / discharging circuit of the battery module; and the temperature of the target battery module can be acquired by a temperature sensor installed on the surface of the target battery module.

[0026] After obtaining the current, voltage, and temperature of the target battery module, the aging degree of the target battery module is determined based on these parameters. For example, when the current undergoes a step change, the voltage and current values ​​before and after the change are determined. Ohm's law R = |ΔV| / |ΔI| is used to calculate the current's current resistance. Then, the current charge is calculated by integrating the current using the ampere-hour integration method. The corresponding State of Charge (SOC) difference is determined based on the voltage change, and the current maximum usable capacity of the target battery module is calculated based on the ratio of the charge to the SOC difference. For example, the SOC difference corresponding to the voltage change can be determined by querying a preset mapping table between the voltage change and the SOC difference. This preset mapping table includes multiple voltage changes and their corresponding SOC differences. Finally, the internal resistance and capacity are corrected based on the temperature. For example, the internal resistance correction coefficient and capacity correction coefficient at the corresponding temperature are found by looking up the table based on the temperature value. The internal resistance and capacity are then corrected based on the internal resistance correction coefficient and capacity correction coefficient respectively (e.g., by calculating the product) to obtain the corrected internal resistance and capacity. Then, the aging degree of the target battery module is calculated based on the corrected internal resistance and capacity. For example, the internal resistance growth rate is calculated based on the ratio between the corrected current internal resistance and the initial internal resistance of the module, and the capacity decay rate is calculated based on the ratio between the corrected capacity and the initial capacity of the module. Finally, the aging degree is calculated based on the internal resistance growth rate and the capacity decay rate. For example, the aging degree = internal resistance growth rate × weight 1 + capacity decay rate × weight 2, where the sum of weight 1 and weight 2 is 1.

[0027] S120, based on the degree of aging and a preset coefficient, calculates the first state-of-charge threshold of the target battery module.

[0028] Specifically, after determining the degree of aging, pre-stored preset coefficients are obtained, such as the first preset coefficient and the second preset coefficient. Based on the first preset coefficient, the second preset coefficient, and the degree of aging, the first state of charge threshold of the target battery module is calculated.

[0029] For example, the degree of aging can be input into the following formula to calculate the first state of charge threshold: First state-of-charge threshold = α × (1 SOH)+β; Where α represents the first preset coefficient; SOH represents the degree of aging; and β represents the second preset coefficient.

[0030] S130, in response to the difference between the state of charge of the target battery cell and the average state of charge of the target battery module being greater than the first state of charge threshold, the target active balancing unit is determined based on the number of the target battery cell, and the first control parameter of the target active balancing unit is determined.

[0031] Specifically, during the charging and discharging process of the target battery module, the state of charge of each target battery cell in the target battery module can be collected by the battery management system, and the average state of charge of all target battery cells can be calculated.

[0032] The state of charge (SOC) of each target battery cell is compared with the mean SOC to determine which target battery cells require SOC balancing. For example, the mean SOC of each target battery cell is subtracted from its SOC to obtain the corresponding difference. If the difference for a target battery cell is greater than a first SOC threshold, it indicates that the target battery cell has a significantly higher charge level than the module average. In this case, the target active balancing unit for that target battery cell needs to be activated to balance its SOC. If the differences for all target battery cells are less than or equal to the first SOC threshold, then no active balancing unit needs to be activated.

[0033] For example, assume the target battery module consists of four cells connected in series, with the following SOC values ​​for each cell: BT1 93%, BT2 85%, BT3 87%, and BT4 84%. The average SOC of the module is (93+85+87+84) / 4 = 87.25%. Assume the first state of charge threshold is 5%. Calculate the difference between the SOC of each cell and the average value of 87.25%: BT1: 93% - 87.25% = 5.75%, the difference is greater than the threshold of 5%, so BT1 is considered to have a high charge level, triggering active balancing; BT2: 85% - 87.25% = -2.25%, the difference is less than the threshold of 5%, so balancing is not triggered; BT3: 87% - 87.25% = -0.25%, the difference is less than the threshold of 5%, so active balancing is not triggered; BT4: 84% - 87.25% = -3.25%, the difference is less than the threshold of 5%, so balancing is not triggered. Based on the above judgment, active balancing is triggered only for BT1, transferring its excess power to other cells, so that the SOC of BT1 gradually drops back to near the average value of the module, thereby achieving consistent adjustment of the state of charge of each cell in the module.

[0034] After identifying the target battery cell requiring active balancing, the target active balancing unit is determined based on the target battery cell's number. For example, assuming the target battery module comprises n target battery cells connected in series, if the 1st or nth target battery cell requires active balancing, only the corresponding boundary active balancing unit is activated. For instance, if the 1st target battery cell requires active balancing, active balancing unit Z1 is determined as the target active balancing unit; if the nth target battery cell requires active balancing, active balancing unit Zn-1 is determined as the target active balancing unit. If the target battery cell numbers requiring active balancing are between 1 and n, two active balancing units can be activated. It should be noted that only one can be activated, or both can be activated simultaneously. For example, if the 1st target battery cell requires active balancing, active balancing units Zi and Zi-1 are determined as the target active balancing units.

[0035] After the target active balancing unit is determined, the first control parameter (such as the activation duration of the active balancing unit) can be determined based on the difference between the state of charge of the target battery cell and the average state of charge. For example, the first control parameter can be determined by querying a preset relationship mapping table between the difference and the first control parameter. The preset relationship mapping table includes multiple differences and the first control parameter corresponding to each difference.

[0036] S140, control the target active balancing unit based on the first control parameters to balance the state of charge of the target battery module.

[0037] Specifically, after determining the first control parameter, the target active balancing unit is driven to work according to the first control parameter. The excess power in the target battery cell is transferred to other cells with low power in the module or fed back to the DC bus through the active balancing unit, so that the SOC of the target battery cell gradually drops back to near the average value of the module, thereby achieving the state of charge balancing of the target battery module.

[0038] This application obtains the state information of the target battery module and determines its aging degree. Based on the aging degree and a preset coefficient, it calculates a first state of charge (SOH) threshold adapted to the current aging state. This threshold is then used to determine the deviation between the SOC of each individual battery cell and the average SOC of the module, triggering active balancing control. By dynamically incorporating the battery aging degree into the balancing decision-making criterion, this solves the problems in related technologies that fail to reflect the nonlinear effects of SOH degradation under different SOC ranges and operating conditions, leading to coarse balancing decisions and difficulty in achieving fine-grained adaptive energy redistribution. This allows the balancing strategy to adaptively adjust according to the battery aging state, maintaining high energy management accuracy and consistency throughout the entire lifecycle of the battery module.

[0039] In some embodiments, the active balancing unit includes an inductor and an inductor direction switching unit. A first end of the inductor is connected to the corresponding target battery cell node, a second end of the inductor is connected to the first end of the corresponding inductor direction switching unit, and the second and third ends of the inductor direction switching unit are respectively connected to the first and second ends of the target battery module. It should be noted that, referring to… Figure 3 The active balancing unit Z1 is used as an example for illustration, but this is not intended to limit the scope of this application.

[0040] Specifically, the active balancing unit Z1 includes an inductor L1 and an inductor direction switching unit Z11. The first end of inductor L1 is connected to the connection node between BT1 and BT2, and the second end of inductor L1 is connected to the first end of inductor direction switching unit Z11. The second end of inductor direction switching unit Z11 is connected to the first end of the target battery module (i.e., the positive terminal of BT1), and the third end of inductor direction switching unit Z11 is connected to the second end of the target battery module (i.e., the negative terminal of BT2).

[0041] It should be noted that the first end of inductor L1 is the first end of active equalization unit Z1, the second end of inductor direction switching unit Z11 is the second end of active equalization unit Z1, and the third end of inductor direction switching unit Z11 is the third end of active equalization unit Z1.

[0042] Specifically, inductor L1, as an energy storage element, is used in the active balancing unit Z1 to achieve bidirectional energy transfer and transmission. When the target battery cell BT1 has a high charge, inductor L1 absorbs energy from the target battery cell BT1 through the target battery cell node and stores it in the form of a magnetic field. The stored energy is then released to the module or transferred to other low-charge cells, thus achieving directional transport of energy from high-charge cells to low-charge areas. The inductor direction switching unit Z11 controls the current flow path in the inductor. By switching the conduction combination of its internal switching transistors, it changes the direction of the inductor current to achieve forward energy transmission or reverse feedback, thereby supporting bidirectional operating modes of cell-to-module balancing or module-to-cell balancing, ensuring that energy flows as needed between any two battery nodes.

[0043] For example, when the target battery cell BT1 needs active balancing, the switching transistor combination within the inductor direction switching unit is first controlled to allow current to flow from the positive terminal of BT1 → inductor direction switching unit → inductor L1 → negative terminal of BT1. In this circuit, BT1 discharges into inductor L1, converting electrical energy into magnetic field energy stored in inductor L1. Subsequently, the switching transistor combination within the inductor direction switching unit is switched, causing the magnetic field energy stored in inductor L1 to be converted back into electrical energy, which is released along the path of inductor L1 → positive terminal of BT2 → negative terminal of BT2 → inductor direction switching unit → inductor L1, transferring the energy to the target battery cell BT2, thereby completing the active balancing of BT1. Through the above control, the SOC of BT1 gradually decreases, ultimately achieving a more consistent state of charge among the cells within the module.

[0044] Thus, this application can achieve bidirectional energy transfer between any target battery cell and module by using a single inductor in conjunction with an inductor direction switching unit. The topology is simple and the number of components is small, which helps to reduce system size and cost.

[0045] In some embodiments, the inductor direction switching unit includes a first switch and a second switch. A first end of the first switch is connected to a first end of the target battery module, and a second end of the second switch is connected to a second end of the target battery module. The connection node between the second end of the first switch and the first end of the second switch is connected to the second end of the inductor. It should be noted that, referring to... Figure 4 The following description uses the inductor direction switching unit Z11 as an example, but it is not intended to limit this application.

[0046] Specifically, the inductor direction switching unit Z11 includes a first switch Z111 and a second switch Z112. The first end of the first switch Z111 is connected to the first end of the target battery module (i.e., the positive terminal of BT1), and the second end of the second switch Z112 is connected to the second end of the target battery module (i.e., the negative terminal of BT2). The connection node between the second end of the first switch Z111 and the first end of the second switch Z112 is connected to the second end of the inductor L1.

[0047] It should be noted that the first end of the inductor direction switching unit Z11 is the connection node between the second end of the first switch Z111 and the first end of the second switch Z112, the second end of the inductor direction switching unit Z11 is the first end of the first switch Z111, and the third end of the inductor direction switching unit Z11 is the second end of the second switch Z111.

[0048] Specifically, when it is necessary to discharge and equalize the target battery cell BT1, the first switch Z111 is turned on and the second switch Z112 is turned off, allowing current to flow from the positive terminal of BT1, through the first switch Z111 into inductor L1, and then through the connection node between BT1 and BT2 into the negative terminal of BT1, forming a discharge loop from BT1 to inductor L1. This converts the electrical energy of BT1 into magnetic field energy stored in inductor L1. Subsequently, the first switch Z111 is turned off and the second switch Z112 is turned on, converting the magnetic field energy stored in inductor L1 into electrical energy. Current flows from the first end of inductor L1 through the connection node between BT1 and BT2 into the positive terminal of BT2, then through the positive terminal to the negative terminal of BT2, and then back through the second switch Z112 to the second end of inductor L1, forming a loop from inductor L1 to BT2, transferring the stored energy to the target battery cell BT2, thus completing the energy transfer from BT1 to BT2. Thus, through the alternating switching control of the above two stages, inductor L1 periodically absorbs energy from high-charge cell BT1 and releases it to low-charge cell BT2, thereby achieving a uniform state of charge among the cells in the module.

[0049] Thus, by alternating the on and off states of the first and second switching transistors, this application can flexibly control the direction of current flow and the energy storage and release states in the inductor, thereby achieving bidirectional energy transfer between individual cells and the module. The number of switching transistors is small and the control timing is simple, which reduces system complexity and hardware cost, while improving energy conversion efficiency. This is beneficial for achieving high integration and low cost active balancing within the limited space of the battery module.

[0050] In some embodiments, the first control parameters include a first conduction duration of the first switch and a second conduction duration of the second switch. Determining the first control parameters of the target active balancing unit includes: calculating the first conduction duration and the second conduction duration based on the target battery cell number, the number of target battery cells in the target battery module, and a preset closing period. Controlling the target active balancing unit based on the first control parameters includes: controlling the first switch and the second switch corresponding to the target active balancing unit based on a preset conduction sequence, the first conduction duration, and the second conduction duration. The preset closing period can be determined according to actual conditions and is not specifically limited here.

[0051] In the following description, the example given is a target battery module consisting of three target battery cells, but this is not intended to limit the scope of this application.

[0052] For example, refer to Figure 5 The target active balancing unit card corresponding to the target battery cell BT2 includes active balancing unit Z2 and active balancing unit Z1.

[0053] When determining the first control parameters of the active balancing unit Z2, the duty cycle of the first switch Z211 is first calculated based on the target battery cell number and the total number of target battery cells in the target battery module. For example, the target battery cell number and the total number of target battery cells in the target battery module can be input into the following formula to calculate the duty cycle of the first switch Z211: ; Where i represents the number of the target battery cell that needs to be actively balanced; N represents the total number of target battery cells in the target battery module; and D2 represents the duty cycle of the first switch Z211 of the active balancing unit Z2. In this embodiment, i=2.

[0054] The duty cycle of the first switch Z211 determines the proportion of its conduction time within a closed cycle. This duty cycle is then multiplied by a preset closed cycle to calculate the first conduction duration. Subtracting the first conduction duration from the preset closed cycle yields the second conduction duration of the second switch Z212. When controlling the active balancing unit Z2 based on the first control parameters, the first switch Z211 is first controlled to conduct for the first duration, allowing inductor L2 to store energy. After the first conduction duration ends, the first switch Z211 is turned off. Then, the second switch Z212 is controlled to conduct for the second duration, allowing inductor L2 to release energy. After the second conduction duration ends, the second switch Z212 is turned off, thus completing one complete closed cycle.

[0055] When determining the first control parameters of the active balancing unit Z1, the duty cycle of the second switch Z112 is first calculated based on the target battery cell number and the total number of target battery cells in the target battery module. For example, the target battery cell number and the total number of target battery cells in the target battery module can be input into the following formula to calculate the duty cycle of the second switch Z112: ; Where i represents the number of the target battery cell that needs to be actively balanced; N represents the total number of target battery cells in the target battery module; and D1 represents the duty cycle of the second switch Z112 of the active balancing unit Z1. In this embodiment, i=2.

[0056] The duty cycle of the second switch Z112 determines the proportion of its conduction time within a closed cycle. This duty cycle is then multiplied by the preset closed cycle to calculate the second conduction duration. Subtracting the second conduction duration from the preset closed cycle yields the first conduction duration of the first switch Z111. When controlling the active balancing unit Z1 based on the first control parameters, the second switch Z112 is first controlled to conduct for the second duration according to the preset conduction sequence, allowing inductor L1 to store energy. After the second conduction duration ends, the second switch Z112 is turned off. Then, the first switch Z111 is controlled to conduct for the first duration, allowing inductor L1 to release energy. After the first conduction duration ends, the first switch Z111 is turned off, thus completing a full closed cycle.

[0057] After both active balancing units Z2 and Z1 perform active balancing operations, they re-determine the difference between the state of charge of the target battery cell BT2 and the average state of charge of the target battery module, and then determine whether to perform the next active balancing.

[0058] Continue to refer to Figure 5 The target active balancing unit card corresponding to the target battery cell BT1 includes an active balancing unit Z1. When determining the first control parameters of the active balancing unit Z1, the duty cycle of the first switch Z111 is first calculated based on the target battery cell number and the total number of target battery cells in the target battery module. For example, the target battery cell number and the total number of target battery cells in the target battery module can be input into the following formula to calculate the duty cycle of the first switch Z111: ; Where i represents the number of the target battery cell that needs to be actively balanced; N represents the total number of target battery cells in the target battery module; and D1 represents the duty cycle of the first switch Z111 of the active balancing unit Z1. In this embodiment, i=1.

[0059] The duty cycle of the first switch Z111 determines the proportion of its conduction time within a closed cycle. This duty cycle is then multiplied by a preset closed cycle to calculate the first conduction duration of the first switch Z111. Subtracting the first conduction duration from the preset closed cycle yields the second conduction duration of the second switch Z112. When controlling the active equalization unit Z1 based on the first control parameters, the first switch Z111 is first controlled to conduct for the first duration, allowing inductor L1 to store energy. After the first conduction duration ends, the first switch Z111 is turned off. Then, the second switch Z112 is controlled to conduct for the second duration, allowing inductor L1 to release energy. After the second conduction duration ends, the second switch Z112 is turned off, thus completing one complete closed cycle.

[0060] After each active balancing operation, the active balancing unit Z1 recalculates the difference between the state of charge of the target battery cell BT1 and the average state of charge of the target battery module, and determines whether to perform the next active balancing operation.

[0061] Continue to refer to Figure 5 The target active balancing unit card corresponding to the target battery cell BT3 includes an active balancing unit Z2. When determining the first control parameters of the active balancing unit Z2, the duty cycle of the second switch Z212 is first calculated based on the target battery cell number and the total number of target battery cells in the target battery module. For example, the target battery cell number and the total number of target battery cells in the target battery module can be input into the following formula to calculate the duty cycle of the second switch Z212: ; Where i represents the number of the target battery cell requiring active balancing; N represents the total number of target battery cells in the target battery module; and D2 represents the duty cycle of the second switch Z212 of the active balancing unit Z2. In this embodiment, i=3.

[0062] The duty cycle of the second switch Z212 determines the proportion of its conduction time within a closed cycle. This duty cycle is then multiplied by the preset closed cycle to calculate the second conduction duration. Subtracting the second conduction duration from the preset closed cycle yields the first conduction duration of the first switch 211. When controlling the active balancing unit Z2 based on the first control parameters, the second switch Z212 is first controlled to conduct for the second duration according to the preset conduction sequence, allowing inductor L2 to store energy. After the second conduction duration ends, the second switch Z212 is turned off. Then, the first switch 211 is controlled to conduct for the first duration, allowing inductor L2 to release energy. After the first conduction duration ends, the first switch 211 is turned off, thus completing a full closed cycle.

[0063] After the active balancing unit Z2 performs active balancing operations, it re-determines the difference between the state of charge of the target battery cell BT3 and the average state of charge of the target battery module, and determines whether to perform the next active balancing.

[0064] Thus, this application determines the conduction time of each switch by calculating the duty cycle based on the individual unit number, so that the magnitude of the equalization current is related to the position of the individual unit in the module, realizing differentiated equalization energy distribution. It can flexibly adapt to the equalization requirements under different module series numbers and different individual unit positions, effectively avoiding the problem of uneven equalization effect of traditional unified equalization strategy for individual units located in different positions of the module.

[0065] In some embodiments, refer to Figure 6The battery balancing system also includes a passive balancing module, which comprises multiple passive balancing units. Each passive balancing unit corresponds one-to-one with a target battery cell, and the passive balancing units are connected in parallel with their corresponding target battery cells. It should be noted that since the passive balancing units correspond one-to-one with the target battery cells, the number of passive balancing units is the same as the number of target battery cells. For example, if the target battery module includes n target battery cells connected in series, then the number of passive balancing units is n. Passive balancing unit 1 performs passive balancing for target battery cell BT1, passive balancing unit 2 performs passive balancing for target battery cell BT2, and so on, with passive balancing unit n performing passive balancing for target battery cell BTn.

[0066] In response to a difference less than or equal to a first state-of-charge threshold and greater than a second state-of-charge threshold, a second control parameter is determined for the passive balancing unit corresponding to the target battery cell. Based on the second control parameter, the passive balancing unit corresponding to the target battery cell is controlled to perform state-of-charge balancing on the target battery module. The second state-of-charge threshold can be determined according to actual conditions; for example, the second state-of-charge threshold can be 0.5%, and the first state-of-charge threshold is greater than the second state-of-charge threshold. No specific restrictions are imposed here.

[0067] Specifically, the state of charge (SOC) of each target battery cell is compared with its mean SOC to determine which target battery cells require SOC balancing. For example, the mean SOC of each target battery cell is subtracted from its SOC to obtain the corresponding difference. If the difference for a target battery cell is less than or equal to a first SOC threshold and greater than a second SOC threshold, then the passive balancing unit corresponding to that target battery cell needs to be activated to balance its SOC.

[0068] For example, assume the target battery module consists of four cells connected in series, with the following state of charge (SOC) values ​​for each cell: BT1 92%, BT2 90%, BT3 88%, and BT4 86%. The average SOC of the module is (92 + 90 + 88 + 86) / 4 = 89%. Assume the first state of charge threshold is 5% and the second state of charge threshold is 0.5%. Calculate the difference between the SOC of each cell and the average 89%: BT1: 92% - 89% = 3%, greater than the second threshold of 0.5% and less than the first threshold of 5%, triggering passive balancing; BT2: 90% - 89% = 1%, greater than the second threshold of 0.5% and less than the first threshold of 5%, triggering passive balancing; BT3: 88% - 89% = -1%, less than the second threshold of 0.5%, not triggering balancing; BT4: 86% - 89% = -3%, less than the second threshold of 0.5%, not triggering balancing. Based on the above judgment, it is determined that the passive balancing units corresponding to BT1 and BT2 are activated, and their excess power is consumed through the balancing resistor, so that their SOC falls back to near the average value; while BT3 and BT4, due to their low SOC, do not undergo passive balancing, thereby achieving consistent adjustment of the state of charge within the module.

[0069] After identifying the target battery cell that needs to be passively balanced, a second control parameter (such as the activation duration of the passive balancing unit) can be determined based on the difference between the state of charge of the target battery cell and the average state of charge. For example, the second control parameter can be determined by querying a preset relationship mapping table between the difference and the second control parameter. The preset relationship mapping table includes multiple differences and the second control parameter corresponding to each difference.

[0070] Thus, this application solves the problem of low balancing efficiency or energy waste caused by relying on a single balancing method in related technologies by setting up passive balancing units that are connected in parallel one-to-one with the target battery cells, and initiating passive balancing when the difference is less than or equal to a first state of charge threshold and greater than a second state of charge threshold. This architecture combines active and passive balancing working in tandem, and the active balancing is used to handle energy transfer under large deviations, while the passive balancing is used to handle fine adjustment under small deviations. The two complement each other, avoiding the frequent switching losses caused by relying entirely on active balancing, and overcoming the drawback of excessively long processing times for single passive balancing when the deviation is large, thus achieving comprehensive optimization of balancing efficiency and energy utilization.

[0071] In some embodiments, the passive equalization unit includes a resistor and a third switch, with the resistor and the third switch connected in series. The second control parameter includes a third closing time of the third switch. Determining the second control parameter of the passive equalization unit corresponding to the target battery cell includes: calculating the third closing time based on the difference and the resistance. Controlling the passive equalization unit corresponding to the target battery cell based on the second control parameter includes: controlling the third switch based on the third closing time. It should be noted that, referring to... Figure 7 The passive equalization unit B1 is used as an example for illustration, but this is not intended to limit the scope of this application.

[0072] Specifically, the passive balancing unit B1 is used to passively balance the target battery cell BT1. The passive balancing unit B1 includes a third switch B11 and a resistor R1. The third switch B11 and resistor R1 are connected in series, and both are connected in parallel with the target battery cell BT1. Specifically, resistor R1 is used to dissipate excess power in the target battery cell BT1, and the third switch B11 is used to control the on / off state of the balancing circuit.

[0073] Furthermore, when the target battery cell BT1 requires passive balancing, the third closing time of the third switch B11 needs to be calculated based on the difference and resistance. For example, the difference reflects the degree to which the SOC of the target battery cell BT1 is higher than the module average. Multiplying this difference by the rated capacity of the target battery cell BT1 estimates the required excess power Q. The passive balancing unit B1 consumes this excess power as heat through resistor R1, with the resistor power consumption P = U² / R, where U is the current terminal voltage of the target battery cell BT1 and R is the known resistance value of resistor R1. Based on the relationship between the excess power Q, the resistor power consumption P, and time (Q = P × t), the third closing time t = Q / P = (difference × rated capacity × R) / U².

[0074] After calculating the third closing time of the third switch B11, the third switch B11 is controlled to conduct for that time, so that the resistor R1 consumes all the excess power within that time, thereby achieving passive equalization control.

[0075] Thus, this application calculates the closing time of the third switch based on the difference between the SOC of the target battery cell and the average value of the module, as well as the resistance value, thereby achieving quantitative control of the equalization power. This avoids, to some extent, the problems of over-equalization or under-equalization under the traditional fixed-time equalization method and improves the equalization accuracy.

[0076] In some embodiments, the method further includes: controlling the first switch, the second switch, and the third switch to be in an off state in response to the difference being less than or equal to a second state of charge threshold.

[0077] Specifically, when the difference between the SOC of the target battery cell and the average SOC of the module is less than or equal to the second state of charge threshold, it indicates that the state of charge of the cell is within a reasonable deviation range relative to the average level of the module, and no balancing operation is required. At this time, it is necessary to control the first and second switches in the active balancing unit and the third switch in the passive balancing unit corresponding to the cell to be all in the off state. This prevents the inductor in the active balancing unit from participating in energy transfer and the resistor in the passive balancing unit from consuming energy, thereby avoiding, to some extent, the additional losses and device fatigue caused by frequent start-stop of the balancing unit due to small fluctuations, while also reducing the overall power consumption of the system.

[0078] As a concrete example, refer to Figure 8 The control method of the battery balancing system in this application embodiment may further include the following steps: S701, begin.

[0079] S702, obtain the status information of the target battery module.

[0080] S703 determines the aging level of the target battery module based on status information.

[0081] S704, calculates the first state of charge threshold of the target battery module based on the degree of aging and the preset coefficient, and determines the second state of charge threshold.

[0082] S705, determine if the difference between the individual cell SOC and the average SOC is greater than the first state of charge threshold. If so, proceed to S707; otherwise, proceed to S706.

[0083] S706, the difference between the individual cell SOC and the average SOC is less than or equal to the first state of charge threshold and greater than the second state of charge threshold. If so, proceed to S708; otherwise, proceed to S709.

[0084] S707, enable active balancing.

[0085] S708, enable passive balance.

[0086] S709, determine whether the balancing is complete. If yes, proceed to S710; otherwise, proceed to S702.

[0087] Specifically, the SOC of each target battery cell and the average SOC of the target battery module are reacquired. The difference between the SOC of each target battery cell and the average SOC of the target battery module is calculated, and the difference is compared with a first state-of-charge threshold and a second state-of-charge threshold to determine whether the equalization process has ended. For example, if the difference is less than or equal to the second state-of-charge threshold, the equalization process is considered complete; otherwise, the equalization process is not considered complete.

[0088] S710, End.

[0089] As another concrete example, taking a target battery cell count of 8 as an illustration, the battery balancing system includes a target battery module, an active balancing module, and a passive balancing module. The target battery module comprises 8 battery cells connected in series (BT1, BT2, BT3, ..., BT8); the active balancing module includes 7 inductors (L1, L2, ..., L7) and 7 first switching transistors (M...). 1,1 ~M 7,1 ) and the second switching transistor (M) 1,2 ~M 7,2 The passive equalization module includes 8 resistors and 8 third-stage switching transistors (M). 1,3 ~M 8,3 ).

[0090] The active balancing mode works as follows: It employs a peak-shaving balancing strategy, discharging cells with high SOC (State of Charge) and transferring their energy to other cells. If the difference between the SOC of cell BT4 and the average SOC of the battery module is greater than the first state of charge threshold, then cell BT4 is identified as the target for active balancing.

[0091] When active balancing is initiated, based on the position of battery cell BT4, the components responsible for performing active balancing are determined to be inductor L4 and the first switching transistor M. 4,1 Second switch M 4,2 Its active balancing process is shown in Figure 9(a1). Referring to Figure 9(a2), for the first switching transistor M... 4,1 Switch analysis, first switch M 4,1 A switching cycle T4 contains two operating phases. The first phase (corresponding to the time period [t]) 4,0 -t 4,1 ]): First switching transistor M 4,1 When the circuit is in the ON state, batteries BT1~BT4 discharge through inductor L4, and the inductor current I4 rises linearly from zero; when t=t 4,1 At that time, the first switching transistor M 4,1 When the circuit is turned off, the inductor current I4 reaches its maximum value. The second stage (corresponding to the time period [t]) 4,1 -t 4,2 ]): First switching transistor M 4,1 When turned off, inductor L4 passes through the second switch M. 4,2 As energy is released to battery packs BT5~BT8, the inductor current I4 gradually decreases, and at t 4,2 When the time drops to zero, the cycle ends.

[0092] When active balancing is initiated, based on the position of battery cell BT4, the components performing active balancing can also be determined to be inductor L3 and the first switching transistor M.3,1 Second switch M 3,2 Its active balancing process is shown in Figure 10(b1). Referring to Figure 10(b2), for the second switch M... 3,2 Switch analysis, second switch M 3,2 A switching cycle T3 contains two operating phases. The first phase (corresponding to time period [t]) 3,0 -t 3,1 ]): Second switching transistor M 3,2 When the circuit is in the ON state, batteries BT4~BT8 discharge through inductor L3, and the inductor current I3 rises linearly from zero; when t=t 3,1 At that time, the second switching transistor M 3,2 When the circuit is turned off, the inductor current I3 reaches its maximum value. The second stage (corresponding to time period [t]) 3,1 -t 3,2 ]): Second switching transistor M 3,2 When turned off, inductor L3 passes through the first switching transistor M. 3,1 As energy is released into the battery pack BT1~BT3, the inductor current I3 gradually decreases, and at t 3,2 When the time drops to zero, the cycle ends.

[0093] It should be noted that when performing active balancing on battery cell BT4, the components that perform active balancing are identified as inductor L4 and the first switching transistor M. 4,1 Second switch M 4,2 Or inductor L3, first switching transistor M 3,1 Second switch M 3,2 Or inductor L4, first switching transistor M 4,1 Second switch M 4,2 And inductor L3, first switching transistor M 3,1 Second switch M 3,2 Among them, inductor L4 and the first switching transistor M 4,1 Second switch M 4,2 And inductor L3, first switching transistor M 3,1 Second switch M 3,2 They can be turned on simultaneously.

[0094] The passive balancing mode works as follows: Each individual battery cell has an independent passive balancing circuit, and multiple individual batteries can discharge simultaneously. If the difference between the SOC of individual battery cell BT4 and the average SOC of the battery module is less than or equal to the first state-of-charge threshold and greater than the second state-of-charge threshold, then the third switch M is controlled. 4,3 After being turned on, the single cell BT4 and the resistor R4 form a circuit, and the energy of the single cell BT4 is dissipated in the form of heat from the resistor.

[0095] In some embodiments, the passive balancing mode control method is as follows: In a passive equalization discharge circuit, through the equalization resistor During discharge, the instantaneous equalization current of passive equalization can be expressed as:

[0096] in, This indicates the voltage across the terminals of a single battery cell; This indicates the resistance value of the equalizing resistor; This represents the instantaneous equalization current.

[0097] In some embodiments, the active balancing mode control method is as follows: By determining the duty cycle of the PWM (Pulse Width Modulation) signal controlling each switch, such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and solving the relationship between the PWM signal cycles of different MOSFET switches, complementary PWM signals are generated, causing the MOSFET switches to turn on alternately, thereby achieving battery module balance. To simplify the theoretical analysis, the following assumptions are introduced: Equal terminal voltage assumption: During the equalization process, the instantaneous effect of battery SOC changes on terminal voltage is ignored, and it is assumed that the terminal voltages of all individual cells are equal. .

[0098] Ideal component assumptions: Neglect the equivalent series resistance of the inductor, and neglect the forward voltage drop of the switching transistor and diode. However, when deriving the current expression, the expression with resistance is given first and then simplified.

[0099] Intermittent operation mode: To ensure that the inductor current can recover to zero in each switching cycle and avoid magnetic saturation and current accumulation, the PWM parameters are designed to make the circuit operate in intermittent conduction mode.

[0100] In actual operating conditions, the above assumptions will introduce some error, but the balancing effect can be guaranteed by limiting the SOC threshold. Let... M i,1 The PWM signal period is Duty cycle is Then the conduction time = The current drop time after shutdown is... ,and .

[0101] Let the cell with the highest SOC in the current battery pack be... Its SOC value is If the following equation is satisfied, then active balancing is initiated:

[0102] in, This represents the average state of charge of the battery pack. This represents the threshold for the first state of charge.

[0103] In the first stage, inductor The voltage across the circuit is determined by Kirchhoff's voltage law. Neglect the line resistance, but retain the inductor's internal resistance. ,but:

[0104] in, This represents the voltage across the i-th inductor in the first stage; This indicates the voltage across the first battery cell; This indicates the voltage across the second battery cell; This represents the voltage across the i-th battery cell; This represents the current in the i-th inductor during the first stage.

[0105] Inductor current satisfies first order Circuit zero-state response:

[0106] in, Let represent the current in the i-th inductor at any time t; This represents the voltage across the i-th inductor; Indicates the start time of the first phase; This indicates the end time of the first stage; L represents the inductance value of the inductor.

[0107] If the inductor's internal resistance is ignored, the current waveform is linear:

[0108] In the second stage, the inductor voltage is:

[0109] in, This represents the voltage across the i-th inductor in the second stage; This represents the voltage across the (i+1)th battery cell; This represents the voltage across the (i+2)th battery cell; This represents the voltage across the Nth battery cell (N represents the total number of battery cells); This represents the current in the i-th inductor during the second stage.

[0110] The inductor discharges to the battery pack through the switching transistor. The circuit has a zero-input response, and the current expression is:

[0111] in, Let represent the current in the i-th inductor at any time t; express The current in the i-th inductor at time i; This represents the voltage across the i-th inductor in the second stage; Indicates the start time of the second phase; This indicates the end time of the second phase.

[0112] If the inductor's internal resistance is ignored, the current waveform is linear:

[0113] Among them, peak current ,in, express The current in the i-th inductor at time i; This represents the voltage across the i-th inductor in the second stage; Indicates the duty cycle of the PWM signal; This represents the PWM signal period corresponding to the i-th active equalization unit.

[0114] The time required for the current to drop to zero is Decision, that is .

[0115] To prevent the inductor from entering continuous conduction mode, it should be ensured that the current has dropped to zero before the end of the cycle, i.e. .Depend on have to:

[0116] Simplifying, we get:

[0117] Under ideal assumptions and Below, there is Substitution have to:

[0118] When equality is applied, the circuit operates in critical continuity mode. Due to line impedance, in practice... Slightly smaller Therefore, according to Choosing the duty cycle using the equal sign ensures that the circuit actually operates in DCM mode. Therefore, the designed duty cycle is:

[0119] At this point, under ideal conditions, the discharge end time is exactly equal to the cycle end time, that is... The inductor current is just intermittent.

[0120] for The same analytical principle applies, so I won't go into detail. Its duty cycle is:

[0121] During one switching cycle, the battery pack BT 1 ~BT i The released electricity corresponds to the green area in Figure 9(a2), and the red area represents... BT i+1 ~BT N The amount of electricity absorbed; BT 1 -BT i-1 The received charge corresponds to the red area in Figure 10(b2), and the green area corresponds to... BT i -BT N Output power. The average current in the four regions mentioned above are as follows: The first green area (inductor) Charging, battery pack - Discharge):

[0122] in, This represents the average current corresponding to the amount of electricity released; This represents the PWM signal period corresponding to the i-th active equalization unit; This represents the current in the i-th inductor during the first stage; Indicates the start time of the first phase; This indicates the end time of the first stage; L represents the inductance value of the inductor. This indicates the duty cycle of the PWM signal; t represents the time of the first stage. This represents the voltage across the i-th inductor in the first stage.

[0123] The first red area (inductance) Discharge, battery pack - Charge):

[0124] in, This represents the average current corresponding to the output current; This represents the PWM signal period corresponding to the i-th active equalization unit; This represents the PWM signal period corresponding to the (i-1)th active equalization unit; This represents the current in the i-th inductor during the second stage; Indicates the start time of the second phase; The value of L represents the end time of the second stage; L represents the inductance value of the i-th inductor; t represents the time of the second stage. This represents the voltage across the i-th inductor in the first stage; This represents the voltage across the i-th inductor in the second stage; This indicates the duty cycle of the PWM signal.

[0125] The second green area (inductor) Charging, battery pack - Discharge):

[0126] in, This represents the average current corresponding to the amount of electricity released; This represents the PWM signal period corresponding to the (i-1)th active equalization unit; Indicates the end time of the first phase; Indicates the start time of the first phase; This represents the current in the (i-1)th inductor during the first stage; This represents the duty cycle of the PWM signal corresponding to the (i-1)th active equalization unit; This represents the PWM signal period corresponding to the (i-1)th active equalization unit; This represents the voltage across the (i-1)th inductor in the first stage; t represents the time of the first stage; and L represents the inductance value of the inductor.

[0127] in, and They are respectively in The duty cycle and period of the PWM signal used in the analysis for The voltage at both ends.

[0128] The second red area (inductance) Discharge, battery pack - Charge):

[0129] in, This represents the average current corresponding to the output current; This represents the PWM signal period corresponding to the (i-1)th active equalization unit; Indicates the start time of the second phase; Indicates the end time of the second phase; This represents the current in the (i-1)th inductor in the second stage; This represents the duty cycle of the PWM signal corresponding to the (i-1)th active equalization unit; This represents the voltage across the (i-1)th inductor in the first stage; L represents the inductance value of the inductor. express The voltage at both ends.

[0130] battery pack The effective equalization charging current is:

[0131] battery pack The effective equalization charging current is:

[0132] intermediate monomers The net balancing current is:

[0133] To ensure as many exceptions as possible Other monomers exhibit consistent SOC changes during the equilibrium process; ideally, this is desirable. and The net charging current of the two battery banks is equal, that is:

[0134] Simplifying, we get the period ratio:

[0135] This formula represents the periodic relationship under normal circumstances. If we substitute it into the formula... and And assume ,but Where U represents the terminal voltage of a single cell (during the equalization process, the instantaneous effect of battery SOC changes on the terminal voltage is ignored, and the terminal voltages of all cells are assumed to be equal), and finally simplified to:

[0136] Using SOC as the balancing variable, and combining an active-passive balancing topology consisting of a battery module, an inductor unit, an inductor direction switching unit composed of multiple MOSFETs, and a resistor unit, along with a SOH-threshold dynamic mapping model and balancing strategy, precise control of the balancing current and mode is achieved through PWM signal control of the MOSFET switches, effectively improving battery pack consistency and extending battery life. In the simulation analysis, the single cell of the series battery pack is a 20Ah lithium iron phosphate battery. The initial SOC is given normally randomizedly with a mean of 0.8, a standard deviation of 0.02, a maximum value of 0.8215, and a minimum value of 0.7764. In the active balancing, the MOSFET switches are all STP220N6F7, with an on-state resistance of 5mΩ, an equivalent internal resistance of 2.5mΩ for the inductor, T=4s, L=1.2H, and an SOC balancing threshold of 0.001. The simulation results of passive balancing based on SOC are as follows: Figure 11 As shown, the simulation results of active equalization based on SOC are as follows: Figure 12 As shown, compared to passive balancing, the balancing current is higher and the balancing speed is faster.

[0137] In some embodiments, the preset coefficients are generated as follows: A search interval, search step size, and convergence accuracy for the first state of charge (SOC) thresholds of multiple test battery modules are determined, wherein the aging degree of each test battery module is different; based on the upper and lower boundaries of the search interval and the search step size, a first candidate SOC threshold and a second candidate SOC threshold for the test battery modules are determined; based on the first and second candidate SOC thresholds, SOC equalization processing is performed on the test battery modules respectively, and performance scores corresponding to the first and second candidate SOC thresholds are calculated based on the equalization processing results; the search interval is updated based on the performance scores, and the first and second candidate SOC thresholds are re-determined based on the updated search interval until the absolute value of the difference between the first and second candidate SOC thresholds is less than the convergence accuracy, and the average of the first and second candidate SOC thresholds is determined as the first SOC threshold of the test battery module; the aging degree of the multiple test battery modules and the corresponding first SOC thresholds are fitted to obtain the preset coefficients.

[0138] Specifically, several test battery cells of the same model and batch as the target battery module are selected, and accelerated aging of the test battery cells is carried out using 1C charge-discharge cycles at 45℃. After a certain number of cycles, a standard capacity test is performed, the current state of charge (SOH) is calculated, and the cycle number and corresponding SOH value are recorded. When the SOH reaches a preset node (e.g., 100%, 95%, 90%, 85%, 80%, 75%, 70%), the aging experiment is paused, and the optimal equalization threshold is determined. For example, several test battery cells (e.g., 4 cells) with the same degree of aging are connected in series to form a test battery module. The equalization system is run under typical HEV operating conditions. The first state of charge threshold that maximizes the extension of cycle life and minimizes the inconsistency of individual cells can be found by the following method.

[0139] First, the search interval, search step size, and convergence accuracy for the first state of charge threshold of multiple test battery modules are determined. The search interval for the first state of charge threshold is as follows: , where L k R represents the upper boundary of the search interval. k This indicates the lower boundary of the search interval and sets the search step size. and convergence accuracy It should be noted that the search interval, search step size, and convergence accuracy of the first state of charge threshold can all be determined according to the actual situation, and no specific restrictions are imposed here.

[0140] Then, based on the upper and lower boundaries of the search interval and the search step size, the first candidate state of charge threshold and the second candidate state of charge threshold for the test battery module are determined. For example, the first candidate state of charge threshold... Second candidate state of charge threshold ,like Then take .

[0141] Then, using the first candidate state of charge threshold M respectively k Second candidate state of charge threshold M' k The battery balancing system of this application is run to perform state-of-charge (POC) balancing on the test battery modules. After the run, the performance scores of the first candidate POC threshold and the second candidate POC threshold are calculated based on the balancing results. and For example, the equalization processing result may include the remaining cycle life and standard deviation of the state of charge (SOC) of the test battery module corresponding to the first candidate SOC threshold, and the remaining cycle life and standard deviation of the SOC of the test battery module corresponding to the second candidate SOC threshold. The remaining cycle life and standard deviation of the SOC of the test battery module corresponding to the first candidate SOC threshold can be input into a preset formula to calculate the performance score of the first candidate SOC threshold. Similarly, the remaining cycle life and standard deviation of the state of charge of the test battery module corresponding to the second candidate state of charge threshold can be input into a preset formula to calculate the performance score of the second candidate state of charge threshold. It should be noted that the SOC of each cell in the test battery module is adjusted to the same pre-set distribution, for example, the SOC of the four cells are 50%, 55%, 60%, and 65% respectively, to ensure that the initial inconsistency is exactly the same for each test.

[0142] Then, the search interval is updated based on the performance scores of the first candidate state of charge threshold and the second candidate state of charge threshold. For example, if the performance score of the first candidate state of charge threshold is relatively high, it means that the first state of charge threshold is among the first candidate state of charge thresholds M. k If the first candidate state of charge threshold is to the left of the first candidate state of charge threshold M, then the search interval is shifted to the left; if the performance score of the second candidate state of charge threshold is relatively high, it indicates that the first state of charge threshold is in the first candidate state of charge threshold M. k If the search range is to the right, then the search range will be shifted to the right.

[0143] Then, the first candidate state of charge threshold and the second candidate state of charge threshold are re-determined based on the updated search interval. The process of determining the first candidate state of charge threshold and the second candidate state of charge threshold has been described in detail in the above embodiments and will not be repeated here.

[0144] Thus, after iterating and updating the first candidate state of charge threshold and the second candidate state of charge threshold as described above, the iteration stops when the absolute value of the difference between the first candidate state of charge threshold and the second candidate state of charge threshold is less than the convergence accuracy. The average value of the first candidate state of charge threshold and the second candidate state of charge threshold is determined as the first state of charge threshold of the test battery module.

[0145] In this embodiment, multiple test battery modules are used to find the first state of charge threshold using the above method to calibrate the aging degree of multiple test battery modules and the first state of charge threshold corresponding to each aging degree. Further, the aging degree of multiple test battery modules and the corresponding first state of charge threshold are fitted to obtain a preset coefficient. For example, multiple sets of data ( A function is fitted, where SOHi represents the aging degree of the i-th test battery module, and Thi represents the first state-of-charge threshold corresponding to the aging degree of the i-th test battery module. Let the independent variable... Convert the calibration data pairs to ( ), using a linear model (e.g. This describes the change of the threshold with aging and uses the least squares method to solve for the preset coefficients, such as the first preset coefficient. Second preset coefficient : ; in, express The arithmetic mean; express The arithmetic mean; n represents the number of battery modules tested. Calculate the coefficient of determination. ,like If a linear model is used, then a piecewise linear interpolation model is accepted; otherwise, piecewise linear interpolation is used. The fitted model is then... It is stored in the non-volatile memory of the BMS in floating-point format.

[0146] In some embodiments, calculating the performance score of the first candidate state of charge threshold and the second candidate state of charge threshold based on the equalization processing result includes: parsing the equalization processing result to obtain the first remaining cycle life of the test battery module and the first state of charge standard deviation of the test battery cells of the test battery module; obtaining the second remaining cycle life of the test battery module and the second state of charge standard deviation of the test battery cells of the test battery module; calculating the life improvement rate of the test battery module based on the first remaining cycle life and the second remaining cycle life; calculating the consistency improvement rate of the test battery module based on the first state of charge standard deviation and the second state of charge standard deviation; and calculating the performance score based on the life improvement rate and the consistency improvement rate.

[0147] Specifically, the equalization processing results include a first equalization processing result and a second equalization processing result. The first equalization processing result is obtained by equalizing the test battery module based on a first candidate state of charge threshold. This first equalization processing result includes the first remaining cycle life of the test battery module and the first state of charge standard deviation of the test battery cells in the test battery module. The first remaining cycle life characterizes the number of cycles the test battery module can continue to cycle from its current state until its capacity decays to 70% of its initial capacity under standard aging conditions of 45°C and 1C. The first remaining cycle life is the number of cycles the test battery module can continue to cycle under these conditions. , This indicates the SOC of each individual battery cell. This represents the average SOC of a single battery cell. Similarly, the second equalization processing result can be obtained by equalizing the test battery module based on the second candidate state of charge threshold. The second equalization processing result also includes the first remaining cycle life and the first state of charge standard deviation of the test battery cells in the test battery module. It should be noted that the performance score of the test battery module corresponding to the first candidate state of charge threshold is calculated using the same method as the performance score of the test battery module corresponding to the second candidate state of charge threshold. In the following description, the calculation of the performance score of the test battery module corresponding to the first candidate state of charge threshold is used as an example, but this is not intended to limit this application.

[0148] Then, the second remaining cycle life of the test battery module and the second state-of-charge standard deviation of the test battery cells of the test battery module are obtained. The second remaining cycle life of the test battery module is the remaining cycle life under the same conditions (e.g., from the current state to the capacity decay to 70% of the initial capacity under 45°C and 1C standard aging conditions) without balancing, and the second state-of-charge standard deviation of the test battery cells of the test battery module is the SOC standard deviation without balancing.

[0149] The calculation method for the first remaining cycle life is as follows: A capacity decay baseline curve for this battery module model under standard aging conditions of 45℃ and 1C is pre-established. This curve records the change in capacity with the number of cycles. During actual testing, the test battery module is subjected to cycle aging tests under these standard conditions. The current capacity is monitored and recorded in real time. When the current capacity decays to 70% of the initial capacity, the total number of cycles at this point is recorded. Subtracting the number of completed cycles from the total number of cycles gives the number of cycles that can continue from the current state until the capacity decays to 70% of the initial capacity. This number is the first remaining cycle life. The method for determining the second remaining cycle life is the same as that for the first remaining cycle life, and will not be elaborated here.

[0150] Then, based on the first remaining cycle life and the second remaining cycle life, the life improvement rate of the test battery module is calculated. For example, the first remaining cycle life and the second remaining cycle life can be input into the following formula to calculate the life improvement rate of the test battery module:

[0151] in, L(M) represents the lifetime improvement rate; L(M) represents the first remaining cycle lifetime. This indicates the second remaining cycle life.

[0152] Then, based on the standard deviation of the first state of charge and the standard deviation of the second state of charge, the consistency improvement rate of the test battery module is calculated. For example, the standard deviation of the first state of charge and the standard deviation of the second state of charge can be input into the following formula to calculate the consistency improvement rate of the test battery module:

[0153] in, Indicates the consistency improvement rate; Indicates the standard deviation of the first state of charge; This represents the standard deviation of the second state of charge.

[0154] Finally, based on the lifetime improvement rate and consistency improvement rate, the performance score of the test battery module corresponding to the first candidate state of charge threshold is calculated. For example, the lifetime improvement rate and consistency improvement rate can be input into the following formula to calculate the performance score:

[0155] in, This represents the performance score of the test battery module corresponding to the first candidate state of charge threshold. Indicates the lifespan improvement rate; Indicates the consistency improvement rate; This represents the weighting coefficient corresponding to the lifespan improvement rate. This represents the weighting coefficient corresponding to the consistency improvement rate. Wherein, , and All can be determined based on the actual situation; no specific restrictions are imposed here.

[0156] In some embodiments, updating the search interval based on the performance score includes: updating the first candidate state of charge threshold as the lower boundary of the search interval in response to the performance score corresponding to the first candidate state of charge threshold being greater than the performance score corresponding to the second candidate state of charge threshold; and updating the first candidate state of charge threshold as the upper boundary of the search interval in response to the performance score corresponding to the second candidate state of charge threshold being greater than the performance score corresponding to the first candidate state of charge threshold.

[0157] For example, the performance score corresponding to the first candidate state of charge threshold is: The performance score corresponding to the second candidate state of charge threshold is .like This indicates that the first state of charge threshold is within On the right, update , The updated interval is Otherwise, the first state of charge threshold is... On the left, update , The updated interval is .

[0158] Corresponding to the above embodiments, this application also proposes a battery balancing system.

[0159] In some embodiments, the battery balancing system includes: a target battery module, an active balancing module, and a controller (not shown). The target battery module includes multiple target battery cells connected in series. The active balancing module includes multiple active balancing units. The first end of the active balancing unit is connected to a corresponding target battery cell node. The target battery cell node is used to characterize the connection node between adjacent target battery cells. The second and third ends of the active balancing unit are connected to the first and second ends of the target battery module, respectively. The controller is used to acquire the state information of the target battery module and calculate the aging degree of the target battery module based on the state information. Based on the aging degree and a preset coefficient, a first state of charge threshold is calculated. In response to the difference between the state of charge of the target battery cell and the average state of charge of the target battery module being greater than the first state of charge threshold, a target active balancing unit is determined based on the number of the target battery cell, and a first control parameter of the target active balancing unit is determined. The target active balancing unit is controlled based on the first control parameter to perform state of charge balancing on the target battery module.

[0160] It should be noted that the above-described embodiments and explanations of the beneficial effects of the control method for the battery balancing system also apply to the battery balancing system of this application. To avoid redundancy, they will not be elaborated in detail here.

[0161] Corresponding to the above embodiments, this application also proposes a computer-readable storage medium.

[0162] The present application provides a computer-readable storage medium storing a battery balancing program that, when executed by a processor, implements the control method according to the aforementioned battery balancing system.

[0163] It should be noted that the above-described embodiments and explanations of the beneficial effects of the control method for the battery balancing system are also applicable to the computer-readable storage medium of the embodiments of this application. To avoid redundancy, they will not be elaborated in detail here.

[0164] Corresponding to the above embodiments, this application also proposes a vehicle.

[0165] See Figure 13 As shown, the vehicle 300 of this application includes a memory 310, a processor 320, and a control program for a battery balancing system stored in the memory 310 and executable on the processor 320. When the processor executes the control program for the battery balancing system, it implements the aforementioned control method for the battery balancing system.

[0166] It should be noted that the above-described embodiments and explanations of the beneficial effects of the control method for the battery balancing system are also applicable to the vehicles described in this application. To avoid redundancy, they will not be elaborated upon here.

[0167] In this application, "multiple" refers to two or more.

[0168] In this application, unless otherwise expressly defined, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0169] The terms “first,” “second,” “third,” “fourth,” etc., in this application (if present) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0170] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0171] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, if the method includes steps A and B, it means that the method may include steps A and B performed sequentially, or it may include steps B and A performed sequentially. For example, if the method may also include step C, it means that step C may be added to the method in any order. For example, the method may include steps A, B, and C, or it may include steps A, C, and B, or it may include steps C, A, and B, etc.

[0172] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A control method for a battery balancing system, characterized in that, The system includes a target battery module and an active balancing module. The target battery module includes multiple target battery cells connected in series. The active balancing module includes multiple active balancing units. The first end of each active balancing unit is connected to a corresponding target battery cell node, and the target battery cell node is used to characterize the connection node between adjacent target battery cells. The second and third ends of each active balancing unit are connected to the first and second ends of the target battery module, respectively. The method includes: Obtain the status information of the target battery module, and determine the aging degree of the target battery module based on the status information; Based on the aging degree and the preset coefficient, the first state of charge threshold of the target battery module is calculated; In response to the difference between the state of charge of the target battery cell and the average state of charge of the target battery module being greater than the first state of charge threshold, a target active balancing unit is determined based on the number of the target battery cell, and a first control parameter of the target active balancing unit is determined. The target active balancing unit is controlled based on the first control parameters to balance the state of charge of the target battery module.

2. The control method for the battery balancing system according to claim 1, characterized in that, The active balancing unit includes an inductor and an inductor direction switching unit. The first end of the inductor is connected to the corresponding target battery cell node, the second end of the inductor is connected to the first end of the corresponding inductor direction switching unit, and the second and third ends of the inductor direction switching unit are respectively connected to the first and second ends of the target battery module.

3. The control method for the battery balancing system according to claim 2, characterized in that, The inductor direction switching unit includes a first switch and a second switch. A first end of the first switch is connected to a first end of the target battery module, and a second end of the second switch is connected to a second end of the target battery module. The connection node between the second end of the first switch and the first end of the second switch is connected to the second end of the inductor. The first control parameter includes a first conduction duration of the first switch and a second conduction duration of the second switch. The determination of the first control parameter of the target active balancing unit includes: calculating the first conduction duration and the second conduction duration based on the number of the target battery cell, the number of target battery cells in the target battery module, and a preset closing period. The step of controlling the target active equalization unit based on the first control parameter includes: Based on the preset conduction sequence, the first conduction duration, and the second conduction duration, the first and second switching transistors corresponding to the target active equalization unit are controlled.

4. The control method for the battery balancing system according to claim 3, characterized in that, The system further includes a passive balancing module, which comprises multiple passive balancing units. Each passive balancing unit corresponds one-to-one with a target battery cell, and the passive balancing unit is connected in parallel with its corresponding target battery cell. The method includes: In response to the difference being less than or equal to the first state of charge threshold and greater than the second state of charge threshold, the second control parameter of the passive equalization unit corresponding to the target battery cell is determined; The passive balancing unit corresponding to the target battery cell is controlled based on the second control parameter to balance the state of charge of the target battery module.

5. The control method for the battery balancing system according to claim 4, characterized in that, The passive equalization unit includes a resistor and a third switch, the resistor and the third switch being connected in series; wherein, the second control parameter includes the third closing time of the third switch, and the second control parameter for determining the passive equalization unit corresponding to the target battery cell includes: Based on the difference and the resistance, the third closing time is calculated; The step of controlling the passive equalization unit corresponding to the target battery cell based on the second control parameter includes: The third switch is controlled based on the third closing duration.

6. The control method for the battery balancing system according to claim 5, characterized in that, The method further includes: In response to the difference being less than or equal to the second state of charge threshold, the first switch, the second switch, and the third switch are controlled to be in the off state.

7. The control method for the battery balancing system according to claim 1, characterized in that, The preset coefficients are generated in the following manner: The search range, search step size, and convergence accuracy of the first state of charge threshold for multiple test battery modules are determined, wherein the aging degree of each test battery module is different. Based on the upper and lower boundaries of the search interval and the search step size, the first candidate state of charge threshold and the second candidate state of charge threshold of the test battery module are determined. Based on the first candidate state of charge threshold and the second candidate state of charge threshold, the test battery module is subjected to state of charge equalization processing, and the performance score corresponding to the first candidate state of charge threshold and the second candidate state of charge threshold is calculated based on the equalization processing result. The search interval is updated based on the performance score, and the first candidate state of charge threshold and the second candidate state of charge threshold are re-determined based on the updated search interval until the absolute value of the difference between the first candidate state of charge threshold and the second candidate state of charge threshold is less than the convergence accuracy. The mean of the first candidate state of charge threshold and the second candidate state of charge threshold is determined as the first state of charge threshold of the test battery module. The aging degree of multiple test battery modules and the first state of charge threshold corresponding to the aging degree are fitted to obtain the preset coefficient.

8. The control method for the battery balancing system according to claim 7, characterized in that, The performance scores for calculating the first candidate state of charge threshold and the second candidate state of charge threshold based on the equalization processing results include: The equalization processing results are analyzed to obtain the first remaining cycle life of the test battery module and the first state-of-charge standard deviation of the test battery cells of the test battery module. Obtain the second remaining cycle life of the test battery module and the second state-of-charge standard deviation of the test battery cells of the test battery module; Based on the first remaining cycle life and the second remaining cycle life, the life improvement rate of the test battery module is calculated; Based on the first standard deviation of state of charge and the second standard deviation of state of charge, the consistency improvement rate of the test battery module is calculated. Based on the lifetime improvement rate and consistency improvement rate, the performance scores of the first candidate state of charge threshold and the second candidate state of charge threshold are calculated.

9. The control method for the battery balancing system according to claim 7, characterized in that, The step of updating the search interval based on the performance score includes: In response to the performance score corresponding to the first candidate state of charge threshold being greater than the performance score corresponding to the second candidate state of charge threshold, the first candidate state of charge threshold is updated to the lower boundary of the search interval; In response to the performance score corresponding to the second candidate state of charge threshold being greater than the performance score corresponding to the first candidate state of charge threshold, the first candidate state of charge threshold is updated to the upper boundary of the search interval.

10. A battery balancing system, characterized in that, include: The system comprises a target battery module, an active balancing module, and a controller. The target battery module includes multiple target battery cells connected in series. The active balancing module includes multiple active balancing units. A first end of each active balancing unit is connected to a corresponding target battery cell node, where the target battery cell node represents the connection node between adjacent target battery cells. The second and third ends of each active balancing unit are connected to the first and second ends of the target battery module, respectively. The controller is used to acquire the status information of the target battery module, calculate the aging degree of the target battery module based on the status information, and calculate the first state of charge threshold based on the aging degree and a preset coefficient. In response to the difference between the state of charge of the target battery cell and the average state of charge of the target battery module being greater than the first state of charge threshold, a target active balancing unit is determined based on the number of the target battery cell, and a first control parameter of the target active balancing unit is determined. The target active balancing unit is then controlled based on the first control parameter to perform state of charge balancing on the target battery module.

11. A computer-readable storage medium, characterized in that, It stores a battery balancing program, which, when executed by the processor, implements the control method of the battery balancing system according to any one of claims 1-9.

12. A vehicle, characterized in that, The system includes a memory, a processor, and a battery balancing program stored in the memory and capable of running on the processor. When the processor executes the battery balancing program, it implements the control method of the battery balancing system according to any one of claims 1-9.

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