Passive Equalization Control Method, Device, Electronic Device and Storage Medium of BMS

Abstract

The present invention provides a passive equalization control method, device, electronic device and storage medium for a BMS, relating to the technical field of batteries. The method includes: obtaining the average discharge voltage corresponding to all battery cells during the previous discharge process, and the average charge voltage corresponding to all battery cells during the previous charge process; determining the discharge voltage deviation corresponding to each battery cell based on the average discharge voltage; determining the charge voltage deviation corresponding to each battery cell based on the average charge voltage; when a first target battery cell belonging to the series device deviation type is identified based on the discharge voltage deviation and charge voltage deviation corresponding to each battery cell, performing sampling voltage calibration on the first target battery cell; and performing passive equalization control on all battery cells including the calibrated first target battery cell. The present invention can correct voltage sampling errors, improve the sampling accuracy of the single-cell voltage, and thus improve the accuracy of the BMS in performing passive equalization control on the battery cells.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a passive equalization control method, device, electronic device, and storage medium for a BMS. Background Art

[0002] A battery management system (BMS) is an important management unit of a battery system, which is used for data monitoring, state estimation, battery equalization, fault diagnosis, charge and discharge control, etc. of the battery. As Figure 1 shown, a battery pack is formed by connecting multiple battery cells in series. Due to the difference in the capacity of each battery cell, based on the "short board effect", battery cells with different power levels will cause the total capacity of the battery pack to decrease. In order to make the power levels of all battery cells as consistent as possible, the equalization function of the BMS is particularly important. Enabling the equalization function means discharging some battery cells with higher power levels separately or charging battery cells with lower power levels.

[0003] Currently, in household energy storage and batteries for smaller-capacity electric appliances, etc., passive equalization technology is adopted, and the electric energy in the single battery cells with larger power levels in the battery system is dissipated through an external circuit to achieve the purpose of power level equalization.

[0004] However, the passive equalization technology is limited by the accuracy of the single-cell voltage. There is internal resistance at the connection between the battery cell and devices such as series-connected copper bars and aluminum bars. The accuracy of the single-cell voltage is affected by the difference in internal resistance and temperature changes, resulting in deviation of the sampled voltage of the battery cell, causing the equalization of the battery cell to be mis-triggered, and thus the accuracy of passive equalization control is relatively low. Summary of the Invention

[0005] The present invention provides a passive equalization control method, device, electronic device, and storage medium for a BMS, aiming to solve the defect in the prior art that the passive equalization technology is limited by the accuracy of the single-cell voltage, there is internal resistance at the connection between the battery cell and devices such as series-connected copper bars and aluminum bars, the accuracy of the single-cell voltage is affected by the difference in internal resistance and temperature changes, resulting in deviation of the sampled voltage of the battery cell, causing the equalization of the battery cell to be mis-triggered, and thus the accuracy of passive equalization control is relatively low.

[0006] The present invention provides a passive equalization control method for a BMS, including:

[0007] Obtaining the average discharge voltage corresponding to all battery cells during the previous discharge process, and the average charge voltage corresponding to all battery cells during the previous charge process;

[0008] Based on the average discharge voltage, determining the discharge voltage deviation corresponding to each battery cell; based on the average charge voltage, determining the charge voltage deviation corresponding to each battery cell;

[0009] In the case of identifying a first target cell belonging to the series device deviation type based on the discharge voltage deviation and the charge voltage deviation corresponding to each cell, perform sampling voltage calibration on the first target cell; the series device deviation type is used to characterize the voltage deviation of the first target cell caused by the internal resistance at the connection between the first target cell and the series device.

[0010] Perform passive equalization control on all cells including the calibrated first target cell.

[0011] According to the passive equalization control method of the BMS provided by the present invention, the identifying the first target cell belonging to the series device deviation type based on the discharge voltage deviation and the charge voltage deviation corresponding to each cell includes:

[0012] For each cell, when the first voltage deviation of the cell is greater than 0 and the second voltage deviation is less than 0, determine the cell as the first target cell belonging to the series device deviation type;

[0013] The first voltage deviation includes the discharge voltage deviation or the charge voltage deviation, the second voltage deviation includes the discharge voltage deviation or the charge voltage deviation, and the deviation categories of the first voltage deviation and the second voltage deviation are different.

[0014] According to the passive equalization control method of the BMS provided by the present invention, the performing sampling voltage calibration on the first target cell includes:

[0015] Obtain the average charge and discharge current corresponding to the first target cell;

[0016] Based on the average charge and discharge current, the discharge voltage deviation, and the charge voltage deviation corresponding to the first target cell, determine the correction calibration coefficient corresponding to the first target cell;

[0017] Based on the correction calibration coefficient, calibrate the sampling voltage of the cell.

[0018] According to the passive equalization control method of the BMS provided by the present invention, the performing passive equalization control on all cells including the calibrated first target cell includes:

[0019] Based on the channel sampling intervals corresponding to each cell and the AC component periods of each cell during charge and discharge, group all cells;

[0020] For each group of cells, based on the cell voltage and the voltage difference of each cell, determine whether to perform equalization control on each cell; the voltage difference is the voltage difference between the cell and the cell with the lowest voltage in the same group.

[0021] According to the passive equalization control method of the BMS provided by the present invention, grouping all the battery cells based on the channel sampling intervals corresponding to each battery cell and the AC component periods of each battery cell during charge and discharge includes:

[0022] Determine the sampling period corresponding to each battery cell based on the sampling times corresponding to each battery cell and the channel sampling interval;

[0023] Determine the target decimal value corresponding to each battery cell based on the sampling period and the AC component period;

[0024] Group the battery cells corresponding to all the target decimal values within a preset range into the same group.

[0025] According to the passive equalization control method of the BMS provided by the present invention, the method further includes:

[0026] When performing equalization control on the battery cells, determine the pressure difference change rate of the battery cells within the target sampling duration;

[0027] Adjust the charging request current of the battery cells during the equalization control based on the pressure difference change rate.

[0028] According to the passive equalization control method of the BMS provided by the present invention, the method further includes:

[0029] When both the discharge voltage deviation and the charging voltage deviation of the battery cell are greater than 0, determine the battery cell as the second target battery cell belonging to the battery cell power deviation type;

[0030] Perform passive equalization control on the second target battery cell when the BMS is in a stationary state.

[0031] The present invention also provides a passive equalization control device for a BMS, including:

[0032] An acquisition module, configured to acquire the average discharge voltage corresponding to all battery cells during the previous discharge process and the average charging voltage corresponding to all battery cells during the previous charging process;

[0033] A determination module, configured to determine the discharge voltage deviation corresponding to each battery cell based on the average discharge voltage; and determine the charging voltage deviation corresponding to each battery cell based on the average charging voltage;

[0034] A calibration module, configured to perform sampling voltage calibration on the first target battery cell when, based on the discharge voltage deviation and the charging voltage deviation corresponding to each battery cell, a first target battery cell belonging to the series device deviation type is identified; the series device deviation type is used to characterize the voltage deviation of the first target battery cell caused by the internal resistance at the connection between the first target battery cell and the series device.

[0035] An equalization control module is used to perform passive equalization control on all cells including the first target cell after calibration.

[0036] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the passive equalization control method of the BMS as described in any one of the above is implemented.

[0037] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the passive equalization control method of the BMS as described in any one of the above is implemented.

[0038] The present invention also provides a computer program product, including a computer program. When the computer program is executed by a processor, the passive equalization control method of the BMS as described in any one of the above is implemented.

[0039] The passive equalization control method, device, electronic device, and storage medium of the BMS provided by the present invention, after obtaining the average discharge voltage corresponding to all cells during the previous discharge process and the average charge voltage corresponding to all cells during the previous charge process, determine the discharge voltage deviation corresponding to each cell according to the average discharge voltage, and determine the charge voltage deviation corresponding to each cell according to the average charge voltage, and identify the voltage deviation type of the first target cell according to the discharge voltage deviation and the charge voltage deviation. In the case where the voltage deviation type of the first target cell is identified as a series device deviation type, calibrate the sampled voltage of the first target cell, and perform passive equalization control on all cells after calibration, correct the voltage sampling error, improve the sampling accuracy of the single-cell voltage, and thus improve the accuracy of the BMS for performing passive equalization control on the cells. Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 It is a schematic connection diagram of a battery pack provided by the prior art.

[0042] Figure 2 It is a schematic diagram of the change of cell voltage and electric quantity provided by the prior art.

[0043] Figure 3 It is a schematic connection diagram of a cell, a copper bar, and an aluminum bar provided by the prior art.

[0044] Figure 4 It is a schematic flow chart of the passive equalization control method of the BMS provided by an embodiment of the present invention.

[0045] Figure 5 It is a schematic diagram of the alternating current component period provided by an embodiment of the present invention.

[0046] Figure 6 It is a schematic structural diagram of the passive equalization control device of the BMS provided by an embodiment of the present invention.

[0047] Figure 7 It is a schematic structural diagram of the electronic device provided by an embodiment of the present invention. Detailed implementation manners

[0048] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] As Figure 2 shown, in the passive equalization control method of the prior art, since there is a certain positive correlation between the cell voltage and the battery charge, generally the non-plateau period of the cell voltage is selected for sampling. The voltage change in the plateau period is small, and the difference in the battery charge of each cell cannot be judged. The specific passive equalization control method includes: sampling the cell voltage in the non-plateau period. When the cell voltage in a certain sampling channel is greater than the voltage threshold, and the voltage difference between this cell and the lowest-voltage cell is greater than the voltage difference threshold, the passive equalization function of this cell can be turned on, that is, the parallel resistor of this cell consumes the battery charge to reduce the charging speed of this cell. After the charging of this cell is completed, the charging stops after triggering the overvoltage of the cell monomer, so that the voltage difference of this cell is reduced, thereby turning off the passive equalization function of this cell.

[0050] However, the passive equalization function of the cell is limited by the monomer voltage accuracy. There is internal resistance at the connection between the cell and devices such as the series-connected copper bars and aluminum bars. The monomer voltage accuracy is affected by the difference in internal resistance and temperature change, resulting in a deviation in the sampled voltage of the cell, causing the cell equalization to be mis-triggered, thereby resulting in low accuracy of the passive equalization control. For example, as Figure 3As shown, the cell voltage of cell 1 = sampling voltage 1 - sampling voltage 0, and the cell voltage of cell 2 = sampling voltage 2 - sampling voltage 1. If the internal resistance at the welding point between the aluminum bar in series with cell 2 and cell 2 is large, it will cause the cell voltage of cell 2 to be too high. The same applies to the copper bar, and the influence of the internal resistance at the welding point between the copper bar and the aluminum bar on the voltage difference will be greater. A too high voltage will cause the cells that originally did not need to perform passive balancing to mistakenly activate passive balancing, resulting in a lower accuracy of passive balancing control.

[0051] In view of the above problems in the prior art, an embodiment of the present invention provides a method for passive balancing control of a BMS. Figure 4 It is a schematic flowchart of the method for passive balancing control of a BMS provided by an embodiment of the present invention. As Figure 4 shown, the method includes the following steps 410 to step 440.

[0052] Step 410, obtain the average discharge voltage corresponding to all cells during the previous discharge process, and the average charge voltage corresponding to all cells during the previous charge process.

[0053] Specifically, obtain the discharge sampling voltages of the cells in each sampling channel during the previous complete discharge process. According to the discharge sampling voltages corresponding to all cells respectively, calculate the average discharge voltage corresponding to all cells during the previous discharge process. The calculation formula for the average discharge voltage is: Ud = (Ud1 + Ud2 +... + Udi +... + Udm) / m. Where Ud represents the average discharge voltage, Udi represents the average value of the discharge sampling voltage of the cell in the i-th sampling channel, and , m represents the total number of sampling channels for sampling.

[0054] At the same time, obtain the charge sampling voltages of the cells in each sampling channel during the previous complete charge process. According to the charge sampling voltages corresponding to all cells respectively, calculate the average charge voltage corresponding to all cells during the previous charge process. The calculation formula for the average charge voltage is: Uc = (Uc1 + Uc2 +... + Uci +... + Ucm) / m. Where Uc represents the average charge voltage, and Uci represents the charge sampling voltage of the cell in the i-th sampling channel.

[0055] Optionally, when calculating the average discharge voltage or average charge voltage corresponding to all battery cells, the calculation method can be selected according to the number of samples in each sampling channel. For example, taking the calculation of the average discharge voltage as an example, when the number of samples corresponding to each sampling channel is different, the average discharge value corresponding to a single battery cell can be calculated based on the discharge sampling voltage corresponding to the single battery cell, and then the average discharge voltage corresponding to all battery cells can be calculated based on all the average discharge values. It can also be to calculate the average value of all the discharge sampling voltages according to the number of samples of all the discharge sampling voltages, and this average value is the average discharge voltage. For example, if the number of samples corresponding to the first sampling channel is 7 and the sum of the 7 discharge sampling voltages is 45, and the number of samples corresponding to the second sampling channel is 9 and the sum of the 9 discharge sampling voltages is 60, then the average discharge voltage can be (45 / 7 + 60 / 9) / 2, or it can be (45 + 60) / (7 + 9). The difference in the number of samples corresponding to each sampling channel may be caused by various reasons such as the battery cell power, data loss, and sampling frequency. When the number of samples corresponding to each sampling channel is the same, there is no difference between the above two methods, and either can be arbitrarily selected. The embodiments of the present invention do not limit this.

[0056] Step 420: Determine the discharge voltage deviation corresponding to each battery cell based on the average discharge voltage; determine the charge voltage deviation corresponding to each battery cell based on the average charge voltage.

[0057] Specifically, after calculating the average discharge voltage and the average charge voltage, for each battery cell, calculate the first difference between the discharge sampling voltage of the battery cell and the average discharge voltage, and this first difference is the discharge voltage deviation of the battery cell. The calculation formula for the discharge voltage deviation of the battery cell in the i-th sampling channel is: Udxi = Udi - Ud, where Udxi represents the discharge voltage deviation of the battery cell in the i-th sampling channel. At the same time, calculate the second difference between the charge sampling voltage of the battery cell and the average charge voltage, and this second difference is the charge voltage deviation of the battery cell. The calculation formula for the charge voltage deviation of the battery cell in the i-th sampling channel is: Ucxi = Uci - Uc, where Ucxi represents the charge voltage deviation of the battery cell in the i-th sampling channel.

[0058] Step 430: In the case of identifying a first target battery cell belonging to the series device deviation type based on the discharge voltage deviation and the charge voltage deviation corresponding to each battery cell, perform sampling voltage calibration on the first target battery cell, where the series device deviation type is used to characterize the voltage deviation of the first target battery cell caused by the internal resistance at the connection between the first target battery cell and the series device.

[0059] Specifically, the voltage deviation caused by the series device deviation type changes with the change of the current direction, that is, the direction of the voltage acting on the internal resistance at the connection between the battery cell and the series device changes with the change of the current direction. For example, when the battery cell is charging, the internal resistance at the connection between the battery cell and the series device will cause the single-cell voltage of the battery cell to be too high, and when the battery cell is discharging, this internal resistance will cause the single-cell voltage of the battery cell to be too low. Therefore, in the embodiments of the present invention, for each battery cell, according to the discharge voltage deviation and the charge voltage deviation corresponding to the battery cell, it is determined whether the voltage deviation type of this battery cell belongs to the series device deviation type. If the voltage deviation type of this battery cell belongs to the series device deviation type, then this battery cell is determined as the first target battery cell. Since the voltage sampling accuracy of the first target battery cell is relatively low, the accuracy of the passive equalization control of the battery cell is relatively low. Therefore, after the first target battery cell is identified, the sampled voltage of the first target battery cell can be calibrated, so as to improve the voltage sampling accuracy of the first target battery cell, thereby avoiding the battery cell from being erroneously triggered for passive equalization.

[0060] Further, the identifying the first target battery cell belonging to the series device deviation type based on the discharge voltage deviation and the charge voltage deviation corresponding to each battery cell includes:

[0061] For each battery cell, when the first voltage deviation of the battery cell is greater than 0 and the second voltage deviation is less than 0, this battery cell is determined as the first target battery cell belonging to the series device deviation type;

[0062] The first voltage deviation includes the discharge voltage deviation or the charge voltage deviation, the second voltage deviation includes the discharge voltage deviation or the charge voltage deviation, and the deviation categories of the first voltage deviation and the second voltage deviation are different.

[0063] Specifically, the deviation categories of the first voltage deviation and the second voltage deviation are different, which can be understood as that the respective power adjustment processes corresponding to the first voltage deviation and the second voltage deviation are different, that is, when the first voltage deviation is the discharge voltage deviation, the second voltage deviation is the charge voltage deviation, and when the first voltage deviation is the charge voltage deviation, the second voltage deviation is the discharge voltage deviation. If the first voltage deviation is greater than 0 and the second voltage deviation is less than 0, it indicates that the voltage of this battery cell changes with the change of the current direction, that is, the voltage deviation type of this battery cell belongs to the series device deviation type, and this battery cell is determined as the first target battery cell.

[0064] It should be noted that during the process where the absolute value of the average charge current of the battery cell is close to the absolute value of the average discharge current, the corresponding first voltage deviation and second voltage deviation can be selected for comparison to determine whether the voltage deviation category of this battery cell belongs to the series device deviation type, so as to improve the accuracy of type identification.

[0065] Further, the sampling voltage calibration for the first target battery cell includes:

[0066] Obtain the average charge-discharge current corresponding to the first target battery cell;

[0067] Based on the average charge-discharge current, discharge voltage deviation, and charge voltage deviation corresponding to the first target battery cell, determine the correction calibration coefficient corresponding to the first target battery cell;

[0068] Calibrate the sampled voltage of the battery cell based on the correction calibration coefficient.

[0069] Specifically, after determining the first target battery cell, the average value of the absolute value of the charging average current and the absolute value of the discharging average current of the first target battery cell can be calculated, and this average value is the average charge-discharge current of the first target battery cell. After calculating the average charge-discharge current, according to the average charge-discharge current, discharge voltage deviation, and charge voltage deviation, calculate the correction calibration coefficient corresponding to the first target battery cell. The calculation formula for the correction calibration coefficient of the first target battery cell is: R = ABS[(Udxi + Ucxi) / 2Ia]. Wherein, R represents the correction calibration coefficient of the first target battery cell, ABS[] represents the absolute value function, and Ia represents the average charge-discharge current of the first target battery cell. After calculating the correction calibration coefficient of the first target battery cell, calibrate the sampled voltage of the first target battery cell. The calibration formula can be: Unn = Un - IR. Wherein, Unn represents the battery cell voltage after calibration of the first target battery cell, Un represents the sampled voltage before calibration of the first target battery cell, and I represents the sampled current of the first target battery cell.

[0070] In the embodiment of the present invention, after obtaining the average discharge voltage corresponding to all battery cells during the previous discharge process and the average charge voltage corresponding to all battery cells during the previous charge process, determine the discharge voltage deviation corresponding to each battery cell according to the average discharge voltage, determine the charge voltage deviation corresponding to each battery cell according to the average charge voltage, and identify the voltage deviation type of the first target battery cell according to the discharge voltage deviation and the charge voltage deviation. When it is identified that the voltage deviation type of the first target battery cell belongs to the series device deviation type, calibrate the sampled voltage of the first target battery cell, correct the voltage sampling error, improve the sampling accuracy of the single cell voltage, and thus improve the accuracy of the BMS for passive equalization control of the battery cells.

[0071] Step 440, perform passive equalization control on all battery cells including the calibrated first target battery cell.

[0072] Specifically, after calibrating the sampled voltage of the first target battery cell, passive equalization control can be performed on all battery cells to maintain the consistency of the battery cells in the battery pack and overcome the "short board effect" of the battery pack.

[0073] In the passive balancing control process, since most of the circuits for charging the battery pack are conversion circuits for alternating current (AC) to direct current (DC). Since the conversion circuit cannot generate stable DC, for example, there is an AC component when the battery pack is connected to an inverter for charging and discharging, which causes large fluctuations in the charging and discharging current, and then causes fluctuations in the sampling voltage. Since the cell voltages of each cell are sampled in turn, that is, there is a channel sampling interval for each cell voltage, the cell voltage fluctuations after sampling are not synchronized, and then the voltage difference of each cell fluctuates greatly, which affects the judgment logic for starting passive balancing. For example, taking the AFE (Analog Front End) chip as an example, the AFE chip uses a fixed frequency to sample the cell voltage of each sampling channel in turn. Take a fixed frequency of 10Hz and a total of 20 sampling channels as an example, that is, the update period is 100ms, and the sampling values ​​of all sampling channels are updated every 100ms, and each sampling channel takes 5ms to sample. When sampling in each sampling channel, the position of the fluctuating voltage is collected randomly, with some sampling channels collecting voltage peaks and some collecting voltage troughs, which results in the voltage difference of the battery cell fluctuating greatly.

[0074] Further, the passive balancing control of all the cells including the calibrated first target cell includes:

[0075] Grouping all the battery cells based on the channel sampling interval corresponding to each of the battery cells and the AC component cycle of each of the battery cells during the charging and discharging process;

[0076] For each group of battery cells, based on the battery cell voltage and the voltage difference of each battery cell, it is determined whether to perform balancing control on each battery cell; the voltage difference is the voltage difference between the battery cell and the lowest voltage battery cell in the same group of battery cells.

[0077] Specifically, in order to address the problem that the charge and discharge current of the battery cell has an AC component, which causes large fluctuations in the voltage difference of the battery cell and affects the judgment logic for turning on passive balancing, in an embodiment of the present invention, the sampling frequency of the battery pack is obtained, and then the update period of the battery pack is calculated based on the sampling frequency. The update period is the reciprocal of the sampling frequency. After calculating the update period of the battery pack, the ratio of the update period to the total number of sampling channels is calculated. The ratio is the channel sampling interval of each battery cell. At the same time, the charge and discharge current is sampled, the average current value within the sampling time is calculated, and the time interval between two times that the current average value is exceeded is determined. The time interval is the AC component period of each battery cell during the charge and discharge process. Figure 5 is a schematic diagram of an AC component cycle provided by an embodiment of the present invention, wherein the AC component cycle is as follows Figure 5As shown. Afterwards, all cells are grouped according to the channel sampling interval and the AC component period, so that the AC component position of each group of cells is the same. For each group of cells, the cell voltage corresponding to each cell is collected, and the lowest voltage cell is determined from the group of cells. The voltage difference between each cell voltage and the lowest voltage cell is calculated, and the voltage difference is the voltage difference of the cell. Since the AC component position of each group of cells is the same, the fluctuation of the voltage difference is reduced, making the voltage difference more stable. Afterwards, the balance judgment is made based on the cell voltage and voltage difference of each cell.

[0078] Furthermore, grouping all the cells based on the channel sampling interval corresponding to each of the cells and the AC component cycle of each of the cells during the charging and discharging process includes:

[0079] Determine a sampling period corresponding to each of the battery cells based on the number of sampling times corresponding to each of the battery cells and the channel sampling interval;

[0080] Based on the sampling period and the AC component period, determining a target decimal value corresponding to each of the battery cells;

[0081] The battery cells corresponding to all target decimal values ​​within the preset range are divided into the same group.

[0082] Specifically, since each battery cell is sampled in turn, the product of the number of sampling times of the battery cell and the channel sampling interval can be calculated. This product is the sampling period when sampling each battery cell, and the sampling period increases with the increase in the number of sampling times. After determining the sampling period, calculate the target decimal value of the quotient of the sampling period and the AC component period. If the target decimal value is within the preset range, it indicates that the AC components of the battery cells corresponding to the target decimal value are in the same position. If the target decimal value is outside the preset range, add 1 to the sampling number, calculate the new sampling period and the new target decimal value, if the new target decimal value is within the preset range, it indicates that the AC components of the battery cells corresponding to the new target decimal value are in the same position. Repeat the above steps to divide the battery cells corresponding to all target decimal values ​​within the preset range into the same group.

[0083] It should be noted that the preset range may be a smaller range to ensure that the AC components within the preset range fluctuate within a very small range near a certain position, so that the AC components within the preset range are regarded as being in the same position. The preset range may be set based on historical experience, for example, the preset range may be [-2%, 2%] or [-5%, 5%], etc., which is not limited in the embodiment of the present invention.

[0084] Further, judging whether to perform balancing control on each of the battery cells based on the battery cell voltage and the voltage difference of each of the battery cells includes:

[0085] For each of the cells, when the cell voltage of the cell is greater than a first preset threshold and the voltage difference is greater than a second preset threshold, perform balancing control on the cell;

[0086] When the cell voltage of the cell is less than the first preset threshold or the voltage difference is less than a third preset threshold, turn off the balancing control of the cell;

[0087] The second preset threshold is greater than the third preset threshold.

[0088] Exemplarily, taking each cell in the battery pack as a lithium iron phosphate battery, the first preset threshold can be 3.4V, the second preset threshold can be 20mV, and the third preset threshold can be 10mV. For each cell, if the cell voltage of the cell is greater than 3.4V and the voltage difference of the cell is greater than 20mV, the passive balancing control of the cell can be enabled. If the cell voltage of the cell is less than 3.4V or the voltage difference of the cell is less than 10mV, the passive balancing control of the cell can be turned off.

[0089] It should be noted that the first preset threshold is the voltage threshold for turning on or off the balancing control, the second preset threshold is the voltage difference threshold for turning on the balancing control, and the third preset threshold is the voltage difference threshold for turning off the balancing control. The embodiments of the present invention do not limit the values of the first preset threshold, the second preset threshold, and the third preset threshold.

[0090] Further, the method further includes:

[0091] When performing balancing control on the cell, determine the rate of change of the voltage difference of the cell within a target sampling duration;

[0092] Based on the rate of change of the voltage difference, adjust the charging request current of the cell during the balancing control process.

[0093] Specifically, after the passive equalization of the battery cell is enabled, since the voltage rise at the end of charging accelerates, especially when the charging current is a large current, from the appearance of voltage difference to start equalization to the shutdown of equalization due to overvoltage protection of the single cell, it generally lasts for several minutes. The equalization duration is short and the amount of equalized power is small, resulting in poor equalization effect. In view of the above problems, in the embodiments of the present invention, after the equalization control of the battery cell is enabled, since the voltage difference continuously changes within the target sampling duration, the rate of change of the voltage difference within the target sampling duration can be calculated, and thus, according to the rate of change of the voltage difference, the charging request current of the battery cell during the equalization control process can be adjusted. For example, if the rate of change of the voltage difference is greater than the fourth preset threshold, it indicates that the voltage difference of the battery cell rises relatively fast. At this time, the charging request current of the battery cell during the equalization control process can be reduced to extend the charging duration, thereby extending the equalization duration. In the case where the rate of change of the voltage difference is less than the fifth preset threshold, the charging request current of the battery cell during the equalization control process is increased to improve the charging efficiency. Based on this, both the charging efficiency and the equalization effect can be taken into account.

[0094] Further, the method further includes:

[0095] In the case where both the discharge voltage deviation and the charging voltage deviation of the battery cell are greater than 0, the battery cell is determined as the second target battery cell belonging to the battery cell power deviation type;

[0096] Perform passive equalization control on the second target battery cell when the BMS is in a stationary state.

[0097] In addition, the voltage deviation type of the battery cell can also include the battery cell power deviation type, which is used to characterize that the voltage of the battery cell is inconsistent with the voltages of other battery cells due to the relatively high power of the battery cell. That is, since there is a certain positive correlation between the battery cell voltage and the power of the battery cell, when the power of the battery cell is relatively high, the battery cell voltage of the battery cell is relatively high, resulting in a relatively large voltage deviation between the battery cell voltage of the battery cell and the battery cell voltages of other battery cells, thereby resulting in poor consistency of the battery cells in the battery pack, and thus resulting in relatively low accuracy of passive control equalization. When the voltage deviation type of the battery cell is the battery cell power deviation type, whether it is the charging process or the discharging process, the battery cell voltage of the battery cell with a higher power is higher than the battery cell voltage of the battery cell with a lower power. Therefore, after determining the discharge voltage deviation and the charging voltage deviation of each battery cell, if both the discharge voltage deviation and the charging voltage deviation of the battery cell are greater than 0, it indicates that the voltage deviation type of the battery cell belongs to the battery cell power deviation type. Thus, the battery cell with the voltage deviation type belonging to the battery cell power deviation type is determined as the second target battery cell, and passive equalization discharge can be performed on the second target battery cell alone when the BMS is in a stationary state.

[0098] In the prior art, since there is no current when the BMS is in the static state, no pressure difference is generated, and the cell voltage is also in the plateau period. Therefore, the BMS in the prior art does not activate the balancing control in the static state. In the embodiments of the present invention, the balancing control is separately performed on the second target chip in the static state, which can extend the balancing duration and thus improve the effect of passive balancing.

[0099] The passive balancing control device of the BMS provided by the present invention will be described below. The passive balancing control device of the BMS described below can be correspondingly referred to the passive balancing control method of the BMS described above.

[0100] Embodiments of the present invention also provide a passive balancing control device of a BMS. Figure 6 is a schematic structural diagram of the passive balancing control device of the BMS provided by the embodiments of the present invention. As Figure 6 shown, the passive balancing control device 600 of the BMS includes: an acquisition module 610, a determination module 620, a calibration module 630, and a balancing control module 640.

[0101] The acquisition module 610 is configured to acquire the average discharge voltage corresponding to all cells during the previous discharge process, and the average charge voltage corresponding to all cells during the previous charge process.

[0102] The determination module 620 is configured to determine the discharge voltage deviation corresponding to each cell based on the average discharge voltage; and determine the charge voltage deviation corresponding to each cell based on the average charge voltage.

[0103] The calibration module 630 is configured to, when identifying a first target cell belonging to the series device deviation type based on the discharge voltage deviation and the charge voltage deviation corresponding to each cell, perform sampling voltage calibration on the first target cell; the series device deviation type is used to characterize the voltage deviation of the first target cell caused by the internal resistance at the connection between the first target cell and the series device.

[0104] The balancing control module 640 is configured to perform passive balancing control on all cells including the calibrated first target cell.

[0105] The passive equalization control device of the BMS provided by the embodiment of the present invention, after obtaining the average discharge voltage corresponding to all battery cells during the previous discharge process and the average charge voltage corresponding to all battery cells during the previous charge process, determines the discharge voltage deviation corresponding to each battery cell according to the average discharge voltage, determines the charge voltage deviation corresponding to each battery cell according to the average charge voltage, and identifies the voltage deviation type of the first target battery cell according to the discharge voltage deviation and the charge voltage deviation. When it is identified that the voltage deviation type of the first target battery cell belongs to the series device deviation type, the sampled voltage of the first target battery cell is calibrated, and after calibration, passive equalization control is performed on all battery cells to correct the voltage sampling error and improve the sampling accuracy of the single - cell voltage, thereby improving the accuracy of the BMS for passive equalization control of the battery cells.

[0106] Optionally, the calibration module 630 is specifically configured to:

[0107] For each of the battery cells, when the first voltage deviation of the battery cell is greater than 0 and the second voltage deviation is less than 0, the battery cell is determined as the first target battery cell belonging to the series device deviation type;

[0108] The first voltage deviation includes the discharge voltage deviation or the charge voltage deviation, the second voltage deviation includes the discharge voltage deviation or the charge voltage deviation, and the deviation categories of the first voltage deviation and the second voltage deviation are different.

[0109] Optionally, the calibration module 630 is specifically configured to:

[0110] Obtain the average charge - discharge current corresponding to the first target battery cell;

[0111] Based on the average charge - discharge current, discharge voltage deviation, and charge voltage deviation corresponding to the first target battery cell, determine the correction calibration coefficient corresponding to the first target battery cell;

[0112] Based on the correction calibration coefficient, calibrate the sampled voltage of the battery cell.

[0113] Optionally, the equalization control module 640 is specifically configured to:

[0114] Group all battery cells based on the channel sampling interval corresponding to each battery cell and the AC component period during the charge - discharge process of each battery cell;

[0115] For each group of battery cells, determine whether to perform equalization control on each battery cell based on the battery cell voltage and voltage difference of each battery cell; the voltage difference is the voltage difference between the battery cell and the battery cell with the lowest voltage in the same group.

[0116] Optionally, the equalization control module 640 is specifically configured to:

[0117] Determine the sampling period corresponding to each battery cell based on the sampling times corresponding to each battery cell and the channel sampling interval;

[0118] Determine the target small value corresponding to each battery cell based on the sampling period and the alternating current component period;

[0119] Divide the battery cells corresponding to all target small values within a preset range into the same group.

[0120] Optionally, the passive equalization control device 600 of the BMS further includes an adjustment module, and the adjustment module is specifically configured to:

[0121] Determine the pressure difference change rate of the battery cell within a target sampling duration when performing equalization control on the battery cell;

[0122] Adjust the charging request current of the battery cell during the equalization control process based on the pressure difference change rate.

[0123] Optionally, the passive equalization control device 600 of the BMS further includes a static equalization module, and the static equalization module is specifically configured to:

[0124] When both the discharge voltage deviation and the charge voltage deviation of the battery cell are greater than 0, determine the battery cell as the second target battery cell belonging to the battery cell power deviation type;

[0125] Perform passive equalization control on the second target battery cell when the BMS is in a stationary state.

[0126] Figure 7 It is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. As Figure 7 shown, the electronic device may include: a processor 710, a communication interface 720, a memory 730, and a communication bus 740. Among them, the processor 710, the communication interface 720, and the memory 730 complete mutual communication through the communication bus 740. The processor 710 can call the logical instructions in the memory 730 to execute the passive equalization control method of the BMS, and this method includes:

[0127] Obtain the average discharge voltage corresponding to all battery cells during the previous discharge process, and the average charge voltage corresponding to all battery cells during the previous charge process;

[0128] Based on the average discharge voltage, determine the discharge voltage deviation corresponding to each battery cell; based on the average charge voltage, determine the charge voltage deviation corresponding to each battery cell;

[0129] When a first target battery cell belonging to the series device deviation type is identified based on the discharge voltage deviation and the charge voltage deviation corresponding to each battery cell, sampling voltage calibration is performed on the first target battery cell; the series device deviation type is used to characterize the voltage deviation of the first target battery cell caused by the internal resistance at the connection between the first target battery cell and the series device.

[0130] Perform passive equalization control on all battery cells including the calibrated first target battery cell.

[0131] In addition, when the logical instructions in the above-mentioned memory 730 can be implemented in the form of software function units and sold or used as an independent product, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0132] On the other hand, the present invention also provides a computer program product. The computer program product includes a computer program that can be stored on a computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the passive equalization control method of the BMS provided by the above-mentioned various methods. The method includes:

[0133] Obtain the average discharge voltage corresponding to all battery cells during the previous discharge process, and the average charge voltage corresponding to all battery cells during the previous charge process;

[0134] Based on the average discharge voltage, determine the discharge voltage deviation corresponding to each battery cell; based on the average charge voltage, determine the charge voltage deviation corresponding to each battery cell;

[0135] When a first target battery cell belonging to the series device deviation type is identified based on the discharge voltage deviation and the charge voltage deviation corresponding to each battery cell, sampling voltage calibration is performed on the first target battery cell; the series device deviation type is used to characterize the voltage deviation of the first target battery cell caused by the internal resistance at the connection between the first target battery cell and the series device.

[0136] Perform passive equalization control on all battery cells including the calibrated first target battery cell.

[0137] In another aspect, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the passive equalization control method of the BMS provided by the above-mentioned various methods. The method includes:

[0138] Obtain the average discharge voltage corresponding to all battery cells during the previous discharge process, and the average charge voltage corresponding to all battery cells during the previous charge process;

[0139] Based on the average discharge voltage, determine the discharge voltage deviation corresponding to each battery cell; based on the average charge voltage, determine the charge voltage deviation corresponding to each battery cell;

[0140] In the case where a first target battery cell belonging to the series device deviation type is identified based on the discharge voltage deviation and the charge voltage deviation corresponding to each battery cell, perform sampling voltage calibration on the first target battery cell; the series device deviation type is used to characterize the voltage deviation of the first target battery cell caused by the internal resistance at the connection between the first target battery cell and the series device;

[0141] Perform passive equalization control on all battery cells including the calibrated first target battery cell.

[0142] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative labor.

[0143] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the above technical solution, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passive balancing control method for BMS, characterized in that: include: Obtain the average discharge voltage of all cells in the previous discharge process, and the average charge voltage of all cells in the previous charge process; Based on the average discharge voltage, determining the discharge voltage deviation corresponding to each of the battery cells; based on the average charge voltage, determining the charge voltage deviation corresponding to each of the battery cells; When a first target cell belonging to a series device deviation type is identified based on the discharge voltage deviation and the charge voltage deviation corresponding to each of the cells, sampling voltage calibration is performed on the first target cell; the series device deviation type is used to characterize the voltage deviation of the first target cell caused by the internal resistance at the connection between the first target cell and the series device; Passive balancing control is performed on all cells including the calibrated first target cell; The passive balancing control of all the cells including the calibrated first target cell comprises: Grouping all the battery cells based on the channel sampling interval corresponding to each of the battery cells and the AC component cycle of each of the battery cells during the charging and discharging process; For each group of battery cells, based on the battery cell voltage and the voltage difference of each battery cell, it is determined whether to perform balancing control on each battery cell; the voltage difference is the voltage difference between the battery cell and the lowest voltage battery cell in the same group of battery cells.

2. The passive balancing control method of BMS according to claim 1, characterized in that: The step of identifying a first target battery cell belonging to a series device deviation type based on the discharge voltage deviation and the charge voltage deviation corresponding to each of the battery cells comprises: For each of the battery cells, when the first voltage deviation of the battery cell is greater than 0 and the second voltage deviation is less than 0, determining the battery cell as a first target battery cell belonging to a series device deviation type; The first voltage deviation includes the discharge voltage deviation or the charge voltage deviation, the second voltage deviation includes the discharge voltage deviation or the charge voltage deviation, and the first voltage deviation and the second voltage deviation are of different deviation types.

3. The passive balancing control method of BMS according to claim 2, characterized in that: The sampling voltage calibration of the first target battery cell includes: Obtaining an average charge and discharge current corresponding to the first target battery cell; Determining a correction calibration coefficient corresponding to the first target battery cell based on an average charge and discharge current, a discharge voltage deviation, and a charge voltage deviation corresponding to the first target battery cell; Based on the correction calibration coefficient, the sampled voltage of the battery cell is calibrated.

4. The passive balancing control method of BMS according to any one of claims 1 to 3, characterized in that: The grouping of all the cells based on the channel sampling interval corresponding to each of the cells and the AC component cycle of each of the cells during the charging and discharging process includes: Determine a sampling period corresponding to each of the battery cells based on the number of sampling times corresponding to each of the battery cells and the channel sampling interval; Based on the sampling period and the AC component period, determining a target decimal value corresponding to each of the battery cells; The battery cells corresponding to all target decimal values ​​within the preset range are divided into the same group.

5. The passive balancing control method of BMS according to any one of claims 1 to 3, characterized in that: The method further comprises: In the case of performing balanced control on the battery cell, determining a pressure difference change speed of the battery cell within a target sampling time; Based on the voltage difference change speed, the charging request current of the battery cell during the balancing control process is adjusted.

6. The passive balancing control method of BMS according to any one of claims 1 to 3, characterized in that: The method further comprises: When the discharge voltage deviation and the charge voltage deviation of the battery cell are both greater than 0, determining the battery cell as a second target battery cell belonging to the battery cell power deviation type; When the BMS is in a static state, passive balancing control is performed on the second target battery cell.

7. A device for implementing the passive balancing control method of a BMS according to any one of claims 1 to 6, characterized in that: include: An acquisition module is used to acquire the average discharge voltage of all cells in the previous discharge process and the average charge voltage of all cells in the previous charge process; A determination module, configured to determine a discharge voltage deviation corresponding to each of the battery cells based on the average discharge voltage; and to determine a charge voltage deviation corresponding to each of the battery cells based on the average charge voltage; A calibration module, for performing sampling voltage calibration on a first target cell when a first target cell belonging to a series device deviation type is identified based on the discharge voltage deviation and the charge voltage deviation corresponding to each of the cells; the series device deviation type is used to characterize the voltage deviation of the first target cell caused by the internal resistance at the connection between the first target cell and the series device; The balancing control module is used to perform passive balancing control on all the cells including the calibrated first target cell.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the passive balancing control method of the BMS according to any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the passive balancing control method of the BMS according to any one of claims 1 to 6 is implemented.

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