A lithium ion battery thermal equalization scheduling method for a BMS

Abstract

The application provides a lithium ion battery thermal equalization scheduling method for a BMS, comprising: using the propagation delay and the attenuation to perform reverse time shift and amplitude restoration on the surface temperature of each battery cell, eliminating the measurement time sequence misalignment caused by the propagation delay, and identifying the theoretical instantaneous temperature of each battery cell synchronized with the inlet temperature fluctuation; subtracting the theoretical instantaneous temperature of each battery cell from the cooling liquid temperature at the position of each battery cell one by one to extract the real-time dynamic temperature difference between each battery cell and the cooling liquid flowing through the position of the battery cell; and outputting the frequency and flow combined disturbance level of the current working condition according to the combination relationship between the preset frequency interval where the frequency amplitude of the main frequency component is located and the preset flow interval where the cooling liquid flow is located.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a lithium-ion battery thermal equalization scheduling method for BMS (Battery Management System). Background Technology

[0002] In the field of battery management systems (BMS), thermal equalization scheduling of lithium-ion batteries is a core element in ensuring battery pack safety and performance. The key lies in precisely controlling the temperature of each cell through a liquid cooling system to prevent localized overheating or undercooling. Currently, the commonly used method is to adjust the coolant flow rate or heat dissipation power based on fixed temperature monitoring points, attempting to reduce the temperature difference between cells. However, these methods often implicitly assume a static state: that the coolant inlet temperature is stable or changes slowly, ignoring the rapid dynamic fluctuations that can occur in actual operation due to external environmental factors or system coupling. This neglect causes the existing solutions to become disconnected from the actual thermal state evolution process when faced with dynamic temperature inputs. Further analysis reveals that when the inlet temperature oscillates, such as with a series of high and low temperature pulses, increasing the flow rate, intended to enhance heat dissipation and reduce the steady-state temperature difference between cells along the flow path, also accelerates the coolant flow velocity in the channel, causing upstream temperature disturbances to be transmitted downstream more quickly. Because of the thermal inertia between each battery cell and the coolant, meaning that temperature response takes time and is delayed, downstream cells often encounter new disturbances that propagate at an accelerated pace before recovering from the previous disturbance. For example, a sudden inlet low-temperature pulse can quickly reach a downstream cell at high flow rates, while that cell may still be recovering from the cooling delay of the previous high-temperature disturbance. The combined effect of these two factors causes abnormally large oscillations in its surface temperature, and in some cases, the temperature fluctuations of downstream cells may even be more severe than those of upstream cells. After the equalization scheduling command based on instantaneous temperature feedback is issued, the actual system heat distribution has already changed at the time of command execution due to the accelerated propagation of temperature disturbances in the flow channel and the time difference in thermal response of each cell. The "temperature snapshot" on which scheduling is based no longer matches the "thermal state reality" at the time of execution, like navigating with an outdated map, which may lead to counterproductive thermal management actions and exacerbate temperature unevenness. For example, after detecting a temperature difference, the upstream system may instruct to increase flow to cool the downstream. However, by the time this is executed, the upstream disturbance has already rapidly reached the downstream, causing the downstream temperature to become even more uncontrolled. Meanwhile, the upstream system, due to the increased flow, becomes overcooled, creating a new imbalance. The control action is not only ineffective but also amplifies the oscillations. This is especially problematic under complex operating conditions with frequent fluctuations in inlet temperature, such as when hybrid vehicles are switching between climbing and descending slopes. In such cases, the accuracy of thermal management drops sharply, potentially leading to thermal runaway. Therefore, under complex operating conditions with dynamically fluctuating coolant inlet temperature and adjustable flow, ensuring that the thermal balance scheduling decisions of the battery management system are synchronized in real time with the constantly evolving actual heat distribution process becomes a key issue in improving the accuracy and reliability of battery pack thermal management. Summary of the Invention

[0003] This invention provides a lithium-ion battery thermal equalization scheduling method for BMS, mainly including: The sampling records of the coolant inlet temperature at the inlet of the liquid cooling module flow channel are obtained, and the main frequency component and current amplitude are analyzed. At the same time, the coolant flow rate, surface temperature of each cell, historical average surface temperature of each cell, coolant temperature at each cell location, series arrangement position of each cell in the liquid cooling flow channel and flow channel length between adjacent cells are obtained. Based on the main frequency component, the current amplitude, and the coolant flow rate, combined with the series arrangement position of each cell in the liquid cooling channel and the channel length between adjacent cells, the propagation delay and attenuation of temperature disturbance from the channel inlet to each cell position along the coolant flow direction are analyzed. Using the propagation delay and attenuation, the surface temperature of each cell is reversed and the amplitude is restored to eliminate the measurement timing misalignment caused by the propagation delay and identify the theoretical instantaneous temperature of each cell that is synchronized with the inlet temperature fluctuation. The theoretical instantaneous temperature of each battery cell is subtracted from the coolant temperature at each battery cell location one by one to extract the real-time dynamic temperature difference between each battery cell and the coolant flowing through that battery cell location. Based on the combination relationship between the preset frequency range where the frequency amplitude of the main frequency component is located and the preset flow range where the coolant flow rate is located, the combined frequency and flow rate disturbance level of the current operating condition is output. When the combined frequency and flow disturbance level reaches the preset high frequency and high flow operating condition level, the sorting basis for the balanced scheduling is switched from the historical average surface temperature of each cell to the absolute amplitude of the real-time dynamic temperature difference. The cells are sorted according to the absolute amplitude of the real-time dynamic temperature difference, and the heat dissipation power allocation ratio of each cell is calculated according to the sorting position and the preset power mapping relationship. The thermal balance scheduling of each cell is then executed.

[0004] Furthermore, the sampling record of the coolant inlet temperature at the inlet of the liquid-cooled module flow channel is obtained, and the dominant frequency component and current amplitude are analyzed. Simultaneously, the coolant flow rate, surface temperature of each cell, historical average surface temperature of each cell, coolant temperature at each cell location, and the series arrangement position of each cell in the liquid-cooled flow channel and the flow channel length between adjacent cells are obtained, including: By deploying a temperature sensor at the inlet of the liquid cooling module flow channel, the inlet temperature of the coolant is continuously collected according to a preset sampling period, and the sampling record containing timestamps and temperature values ​​is obtained. Perform a Fast Fourier Transform on the sampled records and extract the frequency component with the largest amplitude in the frequency domain distribution as the main frequency component; The amplitude of the dominant frequency component in the spectrum is extracted as the current amplitude; The current coolant flow rate is read using a flow sensor; Real-time measurements of the surface temperature of each battery cell are obtained by temperature sensors placed on the surface of each cell. Retrieve the pre-stored historical average value; The coolant temperature readings at each battery cell location are obtained by using temperature probes embedded in the flow channel. The serial arrangement position is determined according to the physical installation sequence of each cell along the coolant flow direction in the liquid-cooled module.

[0005] Furthermore, the analysis of the propagation delay and attenuation of temperature disturbances from the channel inlet to each cell location sequentially along the coolant flow direction, based on the dominant frequency component, the current amplitude, and the coolant flow rate, combined with the series arrangement position of each cell in the liquid cooling channel and the channel length between adjacent cells, includes: The average flow velocity of the coolant in the flow channel is calculated based on the coolant flow rate and the preset cross-sectional area obtained from the liquid cooling system design parameters. The average flow rate is obtained by dividing the coolant flow rate by the preset cross-sectional area; Based on the series arrangement of each battery cell in the liquid cooling channel, the cumulative channel distance from the channel inlet to each battery cell position is sequentially marked along the coolant flow direction; The cumulative flow channel distance is obtained by summing the fixed flow channel length from the inlet to the first cell and the flow channel length between all adjacent cells from the inlet to the first cell segment by segment; Calculate the propagation delay of the temperature disturbance from the channel inlet to each cell location, based on the cumulative channel distance and the average flow velocity. The propagation delay is obtained by dividing the cumulative channel distance by the average flow velocity; According to the order of the series arrangement positions, establish the time delay distribution sequence between the position of each cell and its corresponding propagation time delay; Based on the frequency value of the main frequency component and the cumulative flow channel distance, using an exponential decreasing method with the current amplitude as the initial value and the cumulative flow channel distance as the independent variable, and according to a preset unit distance attenuation ratio and an empirical value based on the thermal conductivity of the material, the attenuated amplitude when the temperature disturbance reaches the position of each cell is calculated segment by segment. The initial value, the cumulative flow channel distance, and the unit distance attenuation ratio are processed according to the preset amplitude attenuation formula to determine the attenuated amplitude. By pairing the propagation delay corresponding to each cell position in the time delay distribution sequence with the attenuated amplitude, a propagation delay and attenuation characteristic describing the temperature disturbance arriving sequentially at each cell position along the coolant flow direction are formed.

[0006] Furthermore, the method of using the propagation delay and attenuation to perform reverse time shifting and amplitude restoration on the surface temperature of each cell, eliminating measurement timing misalignment caused by propagation delay, and identifying the theoretical instantaneous temperature of each cell synchronized with the inlet temperature fluctuation, includes: Based on the propagation delay corresponding to the position of each cell, a reverse time shift operation is performed on the measurement time corresponding to the surface temperature of each cell. By adjusting the measurement time of the surface temperature of each cell by backtracking by one of the propagation delays, the backtracking time corresponding to the surface temperature of each cell is obtained; The retrospective moment represents the original moment when the temperature disturbance felt by the cell occurred at the inlet of the flow channel; For the surface temperature of each cell, the difference between the surface temperature of each cell and the historical average value is extracted to obtain the temperature change corresponding to the temperature disturbance; The attenuated amplitude corresponding to each cell position in the attenuation is used as the ratio to the current amplitude. The reciprocal of this ratio is used to perform a scaling operation on the temperature change to obtain the reduction temperature change of each cell. Match the retrospective time with the change in the reduction temperature according to the one-to-one correspondence of the cell positions; Based on the historical average value corresponding to the surface temperature of each cell, the theoretical instantaneous temperature of each cell is obtained by superimposing the value corresponding to the change in reduction temperature.

[0007] Furthermore, the step of subtracting the theoretical instantaneous temperature of each battery cell from the coolant temperature at each battery cell location one by one to extract the real-time dynamic temperature difference between each battery cell and the coolant flowing through that battery cell location includes: Based on the series arrangement of each battery cell in the liquid cooling channel, the theoretical instantaneous temperature of each battery cell and the coolant temperature at each battery cell position are paired one by one according to the same position number to obtain the temperature pairing combination at each battery cell position. For the temperature pairing combination, the theoretical instantaneous temperature of each cell is subtracted from the coolant temperature corresponding to the cell location to obtain the real-time dynamic temperature difference between each cell and the coolant flowing through the cell location.

[0008] Furthermore, the step of outputting the joint frequency and flow disturbance level of the current operating condition based on the combination relationship between the preset frequency range where the frequency amplitude of the dominant frequency component is located and the preset flow range where the coolant flow rate is located includes: The frequency amplitude of the main frequency component is compared with the preset frequency range boundary to determine the frequency range in which the frequency amplitude is located. At the same time, the flow rate of the coolant is compared with the preset flow rate range boundary to determine the flow rate range in which the coolant flow rate is located. Based on the combination relationship between the preset frequency range and the preset flow range, a preset disturbance level mapping table is queried to obtain the joint disturbance level of frequency and flow under the current operating condition; wherein the disturbance level mapping table is indexed by the pairing data of the preset frequency range and the preset flow range, and the corresponding disturbance level is the output result.

[0009] Furthermore, when the combined frequency and flow disturbance level reaches a preset high-frequency, high-flow operating condition level, the sorting criterion for balanced scheduling is switched from the historical average surface temperature of each cell to the absolute amplitude of the real-time dynamic temperature difference. The cells are then sorted according to the absolute amplitude of the real-time dynamic temperature difference, and the heat dissipation power allocation ratio for each cell is calculated based on the sorting order and a preset power mapping relationship. Thermal balanced scheduling of each cell is then executed, including: In response to the frequency and flow rate joint disturbance level meeting the preset high frequency and high flow rate operating condition level, a sorting basis update instruction is triggered. According to the sorting basis update instruction, the sorting basis for balanced scheduling is changed from the historical average value to the absolute magnitude of the real-time dynamic temperature difference. The absolute magnitude of the real-time dynamic temperature difference is obtained by taking the absolute value of the real-time dynamic temperature difference; Based on the absolute magnitude of the real-time dynamic temperature difference, the cells are sorted in descending order of value to generate the sorting position of each cell. The ranking order represents the relative ranking of the heat exchange intensity of the battery cell at the corresponding time point; The sorting order is processed by a preset power mapping relationship to obtain the heat dissipation power allocation ratio of each battery cell; The power mapping relationship takes the sorting position as input data and the corresponding heat dissipation power allocation ratio as output result. The thermal balance scheduling of each battery cell is performed according to the heat dissipation power allocation ratio.

[0010] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses a thermal equalization scheduling method for lithium-ion batteries in a BMS (Battery Management System). Addressing the impact of coolant temperature fluctuations in liquid-cooled modules on cell thermal management, it integrates temperature disturbance propagation delay and attenuation analysis, real-time dynamic temperature difference extraction, and frequency-flow joint disturbance assessment for various business scenarios. The aim is to solve the problems of misaligned cell temperature measurement timing and thermal imbalance caused by inlet temperature fluctuations. This invention analyzes the dominant frequency component and amplitude of the coolant inlet temperature, combined with the cell series position and flow channel length, to accurately calculate the propagation delay and attenuation of temperature disturbances. It then performs reverse time-shifting and amplitude reconstruction of the cell surface temperature to identify the theoretical instantaneous temperature and extract the real-time dynamic temperature difference with the coolant. Under high-frequency, high-flow conditions, based on the absolute amplitude ranking of the dynamic temperature difference, it dynamically adjusts the heat dissipation power allocation ratio to achieve thermal equalization scheduling. This invention significantly improves battery thermal management accuracy, optimizes cell temperature consistency, and extends battery life. Attached Figure Description

[0011] Figure 1 This is a flowchart of a lithium-ion battery thermal equalization scheduling method for BMS according to the present invention.

[0012] Figure 2 This is a schematic diagram of a lithium-ion battery thermal equalization scheduling method for BMS according to the present invention.

[0013] Figure 3 This is another schematic diagram of a lithium-ion battery thermal equilibrium scheduling method for BMS according to the present invention. Detailed Implementation

[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] like Figures 1-3 This embodiment of a lithium-ion battery thermal equalization scheduling method for BMS may specifically include: S101. Obtain the sampling record of the coolant inlet temperature at the inlet of the liquid-cooled module flow channel, analyze the main frequency component and the current amplitude, and at the same time obtain the coolant flow rate, the surface temperature of each cell, the historical average value of the surface temperature of each cell, the coolant temperature at each cell position, and the series arrangement position of each cell in the liquid-cooled flow channel and the flow channel length between adjacent cells.

[0016] A temperature sensor is deployed at the inlet of the liquid cooling module's flow channel to continuously collect the coolant inlet temperature according to a preset sampling period, obtaining an inlet temperature sampling record containing a timestamp and temperature value. A Fast Fourier Transform is performed on the inlet temperature sampling record to identify the frequency component with the largest amplitude from the frequency domain distribution as the dominant frequency component, and the amplitude corresponding to the dominant frequency component in the spectrum is extracted as the current amplitude. The coolant flow rate value at the current moment is read through a flow sensor, and the real-time measurement value of the surface temperature of each battery cell is obtained from the temperature sensors arranged on the surface of each battery cell. The historical average value of the surface temperature of each battery cell is retrieved from the pre-stored data, and the coolant temperature reading at each battery cell location is obtained from the temperature probes embedded in the flow channel. Based on the physical installation sequence of each cell in the liquid-cooled module along the coolant flow direction, the serial position number of each cell in the series arrangement in the liquid-cooled flow channel is calibrated, the flow channel length parameter between adjacent cells is measured, and the main frequency component, the current amplitude, the coolant flow rate, the surface temperature of each cell, the historical average value, the coolant temperature, the series arrangement position, and the flow channel length are used as input data for thermal equilibrium scheduling.

[0017] In the thermal management process of liquid cooling modules, obtaining inlet temperature sampling records is the foundation for understanding the characteristics of coolant temperature fluctuations.

[0018] For example, a temperature sensor is deployed at the inlet of the liquid cooling module flow channel to continuously collect the temperature of the coolant flowing through that location according to a preset sampling period. Each collection record includes a corresponding timestamp and temperature value, forming an inlet temperature sampling record arranged in chronological order.

[0019] Specifically, a Fast Fourier Transform (FFT) is performed on the inlet temperature sampling records to convert the temperature fluctuation signal in the time domain into a frequency domain representation. The output of the FFT is a spectral distribution, where each frequency component corresponds to an amplitude; a larger amplitude indicates a higher energy proportion of that frequency component in the original signal. The frequency component with the largest amplitude is identified from the spectral distribution and determined as the dominant frequency component, which represents the main oscillation frequency of the inlet temperature fluctuation. Simultaneously, the amplitude corresponding to the dominant frequency component in the spectrum is extracted as the current amplitude, which represents the intensity level of the inlet temperature fluctuation at the current moment.

[0020] In one embodiment, the coolant flow rate is read in real time by a flow sensor deployed in the flow channel, and the surface temperature of each battery cell is measured in real time by a temperature sensor arranged on the surface of each battery cell. The historical average value of the surface temperature of each battery cell is pre-stored in a data buffer and is obtained by averaging the cumulative surface temperatures of each battery cell over a historical sampling period. The coolant temperature at each battery cell location is obtained by a temperature probe embedded in the flow channel at each battery cell location, which measures the actual temperature of the coolant flowing through that battery cell location.

[0021] It should be noted that the serial position number of each battery cell in the liquid cooling channel is determined according to the physical structure of the liquid cooling module. Along the coolant flow direction, each battery cell is numbered sequentially from the channel inlet to the outlet; a smaller number indicates that the cell is closer to the inlet. The channel length parameter between adjacent cells is obtained by measuring the actual distance between two adjacent cells within the channel. This distance reflects the path length of the coolant flowing from one cell position to the next. Furthermore, the main frequency component, current amplitude, coolant flow rate, surface temperature of each cell, historical average value, coolant temperature, serial arrangement position, and channel length are organized into an input data set for thermal equilibrium scheduling. All parameters are aligned according to a unified time base to form a complete thermal state description for the current sampling period.

[0022] S102. Based on the main frequency component, the current amplitude, and the coolant flow rate, and combined with the series arrangement position of each cell in the liquid cooling channel and the channel length between adjacent cells, analyze the propagation delay and attenuation of temperature disturbance from the channel inlet to each cell position sequentially along the coolant flow direction.

[0023] Based on the coolant flow rate and the preset cross-sectional area of ​​0.01 square meters obtained from the liquid cooling system design parameters, the average flow velocity of the coolant in the flow channel is calculated. The average flow velocity is obtained by dividing the coolant flow rate by the preset cross-sectional area. Combining the series arrangement of each battery cell in the liquid cooling flow channel, the cumulative flow channel distance from the flow channel inlet to each battery cell position is sequentially marked along the coolant flow direction. The cumulative flow channel distance is obtained by adding the fixed flow channel length of 0.1 meters from the inlet to the first battery cell to the flow channel lengths between all adjacent battery cells from the inlet to that battery cell, segment by segment. For the cumulative flow channel distance and the average flow velocity, the propagation delay of temperature disturbance from the flow channel inlet to each battery cell position is calculated. The propagation delay is obtained by dividing the cumulative flow channel distance by the average flow velocity. According to the order of the series arrangement, a time delay distribution sequence between each battery cell position and its corresponding propagation delay is established. Based on the frequency value of the dominant frequency component and the cumulative flow channel distance, an exponential decreasing method is used, with the current amplitude as the initial value and the cumulative flow channel distance as the independent variable. Following a preset attenuation ratio per unit distance, and based on the empirical value of the material's thermal conductivity (0.05 per meter), the attenuated amplitude of the temperature disturbance reaching each cell position is calculated segment by segment. The calculation formula is Ad = A0 * exp(-k * d), where Ad is the attenuated amplitude, A0 is the initial amplitude, k is the attenuation ratio, and d is the cumulative flow channel distance. The propagation delay corresponding to each cell position in the time delay distribution sequence is paired with the attenuated amplitude to form a description of the propagation delay and attenuation of the temperature disturbance sequentially reaching each cell position along the coolant flow direction.

[0024] In the thermal management process of liquid-cooled modules, the time delay and attenuation characteristics of temperature disturbances propagating from the inlet of the flow channel along the coolant flow direction to each cell directly affect the accuracy of thermal balance scheduling.

[0025] For example, when the coolant inlet temperature fluctuates, the fluctuation is transmitted downstream via the coolant. Cells at different locations experience temperature changes at different times due to their varying distances from the inlet, and the fluctuation amplitude gradually weakens as the propagation distance increases.

[0026] Specifically, the average flow velocity of the coolant within the flow channel is a key parameter determining how quickly temperature disturbances propagate. The average flow velocity is obtained by the ratio of the coolant flow rate to the cross-sectional area of ​​the flow channel, where the cross-sectional area of ​​the flow channel is a fixed value predetermined during the design of the liquid cooling module, typically characterized by the inner diameter of the flow channel or its equivalent flow area.

[0027] In one embodiment, if the coolant flow rate is a certain number of liters per minute and the cross-sectional area of ​​the flow channel is a preset value in the square millimeter range, the average flow velocity is expressed in meters per second. This flow velocity value reflects the rate at which the coolant carrying temperature information moves downstream along the flow channel.

[0028] In one possible implementation, the cumulative flow path distance is calculated based on the series arrangement of each battery cell in the liquid-cooled flow path. The series arrangement positions are numbered sequentially according to the direction of coolant flow from the inlet to the outlet; a larger number indicates that the battery cell is farther from the inlet. For any given battery cell, starting from the flow path inlet, the flow path lengths between all adjacent cells between that cell and the inlet are summed segment by segment to obtain the cumulative flow path distance at that cell's location.

[0029] For example, in a liquid-cooled module, multiple battery cells are arranged in series. The flow channel length between adjacent battery cells is determined according to the physical structure of the module. Then, the cumulative flow channel distance of the battery cell located in the third position is equal to the flow channel length between the first and second battery cells plus the flow channel length between the second and third battery cells.

[0030] It should be noted that propagation delay characterizes the time required for a temperature disturbance to travel from the inlet of the flow channel to a specific cell location. This propagation delay is calculated by dividing the cumulative flow channel distance by the average flow velocity, and physically represents the time it takes for the coolant to carry the temperature fluctuation information from the inlet along that distance. In actual liquid cooling systems, cells closer to the inlet have shorter cumulative flow channel distances and correspondingly shorter propagation delays, meaning these cells sense changes in the inlet temperature more quickly. Conversely, cells farther from the inlet have longer cumulative flow channel distances and larger propagation delays, resulting in a significant lag in temperature response. By arranging the propagation delay values ​​of each cell according to their series configuration, a delay distribution sequence is formed. This sequence clearly shows the sequential arrival time of the temperature disturbance along the flow channel at each cell location.

[0031] Preferably, the amplitude of the temperature disturbance does not remain constant during its propagation along the flow channel, but gradually decreases with increasing propagation distance. This decrease originates from the continuous heat exchange between the coolant and the flow channel wall and the cell surface, causing the energy of the temperature fluctuation to dissipate continuously during transmission. An exponential decrease is a commonly used method to describe this decrease, characterized by a decrease rate proportional to the current amplitude; the decrease becomes more pronounced with increasing distance but never drops to zero.

[0032] In one embodiment, the current amplitude at the inlet is used as the initial amplitude, and the cumulative flow channel distance is used as the independent variable. The attenuated amplitude at each cell location is calculated segment by segment according to a preset attenuation ratio per unit distance. The attenuation ratio per unit distance reflects the percentage decrease in temperature fluctuation amplitude after the coolant flows through a unit length of flow channel. This ratio is determined by a combination of factors such as the heat exchange efficiency of the liquid cooling system and the thermal conductivity of the flow channel material.

[0033] Understandably, cells closer to the inlet have a smaller cumulative flow path distance, resulting in less attenuation of temperature disturbances and amplitudes close to the current amplitude at the inlet. Conversely, cells farther from the inlet have a larger cumulative flow path distance, leading to multiple stages of attenuation and accumulation of temperature disturbances, resulting in amplitudes significantly lower than the inlet amplitude. This amplitude reduction characteristic along the flow path makes the temperature fluctuation intensity felt by downstream cells weaker than that of upstream cells. Furthermore, by pairing the propagation delay corresponding to each cell position in the time delay distribution sequence with the attenuated amplitude at that position, a complete description of propagation delay and attenuation is formed.

[0034] In one possible implementation, each cell location corresponds to a set of data, including the propagation delay and attenuated amplitude at that location. The data for all cell locations are arranged in series, forming complete information describing the propagation characteristics of temperature disturbances along the coolant flow direction. This information indicates that for any temperature fluctuation occurring at the inlet at any given time, the propagation delay can be used to predict when the fluctuation will reach each cell location, and the attenuated amplitude can be used to predict the intensity of the fluctuation upon arrival. By obtaining the propagation delay and attenuation characteristics, the spatiotemporal propagation pattern of temperature disturbances in the liquid-cooled module can be quantitatively characterized, providing a basis for timing synchronization and amplitude correction for subsequent thermal equilibrium scheduling based on disturbance propagation characteristics.

[0035] S103. Using the propagation delay and the attenuation, reverse time shift and amplitude restoration are performed on the surface temperature of each cell to eliminate the measurement timing misalignment caused by the propagation delay and identify the theoretical instantaneous temperature of each cell that is synchronized with the inlet temperature fluctuation.

[0036] Based on the propagation delay corresponding to the location of each cell, a reverse time-shift operation is performed on the measurement time of the surface temperature of each cell, shifting the measurement time of each cell's surface temperature back by one propagation delay to obtain the backtracked time corresponding to each cell's surface temperature. This backtracked time represents the original time when the temperature disturbance felt by the cell occurred at the flow channel inlet. For the measured value of each cell's surface temperature, the measured value is subtracted from the historical average value of each cell's surface temperature to obtain the temperature change caused by the inlet temperature fluctuation. Using the ratio between the attenuated amplitude corresponding to each cell location and the current amplitude in the attenuation mechanism, the temperature change is amplified according to the reciprocal of this ratio to obtain the reduced temperature change of each cell. The backtracked time and the reduced temperature change are mapped one-to-one according to the cell location. Using the historical average value of each cell's surface temperature as a benchmark, the reduced temperature change is superimposed to obtain the theoretical instantaneous temperature of each cell synchronized with the inlet temperature fluctuation.

[0037] In the thermal management process of liquid-cooled modules, there is a time-series misalignment in the measured surface temperatures of each cell. That is, although the temperature measurements of cells at different locations are collected at the same time, they actually reflect the impact of inlet temperature fluctuations at different historical moments. The purpose of the reverse time-shift operation is to restore the measurement time of each cell to the original moment when the disturbance it sensed occurred.

[0038] Specifically, the reverse time-shift operation moves the measurement time backward by the corresponding amount of time according to the propagation delay corresponding to the position of each cell.

[0039] For example, if a battery cell is located in the middle of the flow channel and its propagation delay is several seconds, then the inlet disturbance reflected by the surface temperature measurement of the battery cell at the current moment actually occurred several seconds before the current moment. By tracing the measurement moment back to this propagation delay, the obtained backtracked moment is the original moment when the temperature fluctuation at the inlet occurred, and the backtracked moments of each battery cell uniformly point to the same inlet disturbance event.

[0040] In one possible implementation, the temperature change is extracted by subtracting the measured surface temperature of each cell from its historical average. The historical average represents the temperature reference for that cell under steady-state conditions, and the difference between the measured value and the historical average is the transient temperature shift caused by inlet temperature fluctuations. This temperature change decays during propagation, and its magnitude is smaller than the temperature change that the original fluctuation at the inlet should have caused.

[0041] It should be noted that the amplitude restoration operation amplifies the temperature change by using the reciprocal of the ratio between the attenuated amplitude and the current amplitude. The attenuated amplitude reflects the actual intensity of the temperature disturbance when it reaches the cell location, while the current amplitude reflects the original disturbance intensity at the inlet. The ratio of the two characterizes the degree of amplitude preservation during the disturbance propagation process. Using the reciprocal of this ratio as an amplification factor, the attenuated temperature change is restored to the inlet disturbance level, resulting in the restored temperature change. Furthermore, the retrospective time of each cell is mapped one-to-one with the restored temperature change according to the cell location, and the restored temperature change is superimposed on the historical average value to obtain the theoretical instantaneous temperature of each cell. This theoretical instantaneous temperature characterizes the temperature state of each cell after eliminating the effects of propagation delay and amplitude attenuation, maintaining time synchronization with the inlet temperature fluctuation, providing a temperature reference under a unified time base for thermal equilibrium scheduling.

[0042] S104. Subtract the theoretical instantaneous temperature of each battery cell from the coolant temperature at each battery cell location one by one to extract the real-time dynamic temperature difference between each battery cell and the coolant flowing through that battery cell location.

[0043] Based on the series arrangement of each battery cell in the liquid cooling channel, the theoretical instantaneous temperature of each battery cell and the coolant temperature at each battery cell location are paired one by one according to the same position number to obtain a temperature pairing combination for each battery cell location. For each temperature pairing combination, the theoretical instantaneous temperature of each battery cell is subtracted from the coolant temperature corresponding to that battery cell location to obtain the real-time dynamic temperature difference between each battery cell and the coolant flowing through that battery cell location.

[0044] In the thermal management process of liquid-cooled modules, the difference between the theoretical instantaneous temperature of each cell and the coolant temperature at each cell location reflects the heat transfer driving force between the cell and the coolant.

[0045] For example, the theoretical instantaneous temperature characterizes the temperature state of the cell after eliminating propagation delay and synchronizing with the inlet temperature fluctuation, while the coolant temperature characterizes the actual temperature of the coolant flowing through the cell location.

[0046] Specifically, the temperature pairing combinations are established based on the serial position number of each cell in the series arrangement of the liquid cooling channel. Each cell position corresponds to a theoretical instantaneous temperature value and a coolant temperature value. The two are paired according to the same position number to form a one-to-one temperature data combination.

[0047] In one embodiment, a subtraction operation is performed on the temperature pairings, subtracting the coolant temperature corresponding to the cell's location from the theoretical instantaneous temperature of each cell. The resulting difference is the real-time dynamic temperature difference between the cell and the coolant. A positive temperature difference indicates that the cell temperature is higher than the coolant temperature, and the cell releases heat to the coolant; a negative temperature difference indicates that the cell temperature is lower than the coolant temperature, and the coolant transfers heat to the cell. The real-time dynamic temperature difference accurately reflects the heat exchange state between each cell and the coolant at the current moment.

[0048] S105. Based on the combination relationship between the preset frequency range where the frequency amplitude of the main frequency component is located and the preset flow range where the coolant flow rate is located, output the joint frequency and flow rate disturbance level of the current operating condition.

[0049] Based on the frequency amplitude of the dominant frequency component, a preset frequency range boundary is compared to determine the frequency range in which the frequency amplitude falls. Simultaneously, based on the coolant flow rate, a preset flow rate range is compared to determine the flow rate range in which the coolant flow rate falls. Based on the combination relationship between the frequency range and the flow rate range, a preset disturbance level mapping table is consulted. This disturbance level mapping table uses the pairing of frequency ranges and flow rate ranges as an index and the disturbance level as the output to obtain the joint frequency and flow disturbance level for the current operating condition.

[0050] In the thermal management of liquid cooling modules, determining the combined disturbance level of frequency and flow rate is a key step in identifying operating conditions.

[0051] For example, the frequency range is divided according to the frequency amplitude of the main frequency component of the inlet temperature fluctuation. The preset frequency range boundary divides the frequency amplitude range into low frequency range, mid frequency range and high frequency range. By comparing the frequency amplitude of the main frequency component with the boundary of each range, the frequency range in which it is located is determined.

[0052] Specifically, the flow rate range is divided based on the coolant flow rate value. Preset flow rate range boundaries divide the flow range into low-flow, medium-flow, and high-flow ranges. The current coolant flow rate is compared with the boundaries of each range to determine its current flow rate range. The frequency range and flow rate range together constitute a description of the disturbance characteristics of the current operating condition.

[0053] In one embodiment, a disturbance level mapping table is pre-established, with each row in the table corresponding to a combination of frequency range and flow range, and each combination corresponding to a disturbance level.

[0054] For example, the combination of a high-frequency range and a high-flow range corresponds to a high-frequency, high-flow operating condition level, while the combination of a low-frequency range and a low-flow range corresponds to a low-frequency, low-flow operating condition level. Based on the determined frequency and flow ranges, the corresponding disturbance level is looked up in the mapping table, and the combined frequency and flow disturbance level of the current operating condition is output.

[0055] S106. When the frequency and flow rate combined disturbance level reaches the preset high frequency and high flow rate operating condition level, the sorting basis for the balanced scheduling is switched from the historical average surface temperature of each cell to the absolute amplitude of the real-time dynamic temperature difference. The cells are sorted according to the absolute amplitude of the real-time dynamic temperature difference, and the heat dissipation power allocation ratio of each cell is calculated according to the sorting position and the preset power mapping relationship. The thermal balance scheduling of each cell is then executed.

[0056] If the combined frequency and flow disturbance level reaches a preset high-frequency, high-flow operating condition level, the sorting criterion for balanced scheduling is switched, changing the sorting criterion from the historical average surface temperature of each cell to the absolute amplitude of the real-time dynamic temperature difference. The absolute amplitude of the real-time dynamic temperature difference is obtained by taking the absolute value of the real-time dynamic temperature difference. Based on the absolute amplitude of the real-time dynamic temperature difference, each cell is sorted in descending order of value to obtain its ranking. The ranking represents the relative ranking of the cell's heat exchange intensity at the current moment; the larger the absolute amplitude value, the higher the ranking. Based on the ranking and a preset power mapping relationship, the heat dissipation power allocation ratio for each cell is determined. The power mapping relationship takes the ranking as input and the heat dissipation power allocation ratio as output; cells with higher rankings correspond to a higher heat dissipation power allocation ratio, and thermal balanced scheduling of each cell is performed according to the heat dissipation power allocation ratio. The power mapping relationship is calculated using a linear decreasing function: Let N be the total number of cells, rank... k Given the ranking of the k-th cell (1 being the highest), the heat dissipation power allocation ratio pk = (N - rank) k +1) / S, where S=∑{j=1} N (N-j+1)=N(N+1) / 2 is the normalization factor. Taking N=12 as an example, when rank=1, p=12 / 78≈0.154, when rank=6, p=7 / 78≈0.090, when rank=12, p=1 / 78≈0.013, and the sum is 1.

[0057] In the thermal management process of liquid-cooled modules, when the inlet temperature fluctuates frequently and the coolant flow rate is large, the sorting criteria based on historical average values ​​are difficult to reflect the real-time heat exchange status of each cell.

[0058] For example, the high-frequency and high-flow-rate operating condition level characterizes a combined state in which the main frequency component of the inlet temperature fluctuation is in a higher frequency range and the coolant flow rate is in a larger flow range. At this time, the propagation speed of temperature disturbance in the flow channel is accelerated, and the temperature response of each cell exhibits rapid dynamic change characteristics.

[0059] Specifically, when the combined disturbance level of frequency and flow reaches the preset high-frequency, high-flow operating condition level, the sorting criteria for balanced scheduling are switched. Under normal operating conditions, the sorting criteria use the historical average surface temperature of each cell, which reflects the temperature level of the cell over a longer time scale. Under high-frequency, high-flow operating conditions, the sorting criteria switch to the absolute amplitude of the real-time dynamic temperature difference, which reflects the intensity of heat exchange between the cell and the coolant at the current moment.

[0060] In one embodiment, the absolute magnitude of the real-time dynamic temperature difference is obtained by taking the absolute value of the real-time dynamic temperature difference. The larger the absolute magnitude, the more significant the temperature difference between the cell and the coolant, and the stronger the heat exchange driving force. The cells are sorted in descending order of their absolute magnitude values ​​to obtain their ranking. A ranking of 1 indicates that the absolute magnitude of that cell is the largest among all cells.

[0061] It should be noted that the power mapping relationship specifies the correspondence between the sorting order and the heat dissipation power allocation ratio.

[0062] In one possible implementation, the power mapping relationship adopts a linear decreasing method, where cells ranked higher in the order are allocated a higher proportion of heat dissipation power, and cells ranked lower in the order are allocated a lower proportion of heat dissipation power.

[0063] For example, a liquid-cooled module contains several battery cells arranged in series. The battery cell ranked first is allocated the highest proportion of heat dissipation power, while the battery cell ranked last is allocated the lowest proportion of heat dissipation power, with the sum of the heat dissipation power proportions of all cells being 100%. Furthermore, thermal balance scheduling is performed according to the heat dissipation power allocation proportions of each battery cell. This is achieved by adjusting the opening of the valves in the coolant flow channels passing through each battery cell or adjusting the power of the corresponding auxiliary cooling devices, thus enabling differentiated control of the heat dissipation capacity of each battery cell and providing stronger heat dissipation support to the cells with higher heat exchange intensities.

[0064] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the spirit and scope of the embodiments of this application. Therefore, if these modifications and variations to the embodiments of this application fall within the scope of the claims of this application and their equivalents, this application also intends to include these modifications and variations.

Claims

1. A thermal equilibrium scheduling method for lithium-ion batteries oriented towards BMS, characterized in that, The method includes: The sampling records of the coolant inlet temperature at the inlet of the liquid cooling module flow channel are obtained, and the main frequency component and current amplitude are analyzed. At the same time, the coolant flow rate, surface temperature of each cell, historical average surface temperature of each cell, coolant temperature at each cell location, series arrangement position of each cell in the liquid cooling flow channel and flow channel length between adjacent cells are obtained. Based on the main frequency component, the current amplitude, and the coolant flow rate, combined with the series arrangement position of each cell in the liquid cooling channel and the channel length between adjacent cells, the propagation delay and attenuation of temperature disturbance from the channel inlet to each cell position along the coolant flow direction are analyzed. Using the propagation delay and attenuation, the surface temperature of each cell is reversed and its amplitude restored to eliminate measurement timing misalignment caused by propagation delay, and to identify the theoretical instantaneous temperature of each cell synchronized with the inlet temperature fluctuation, including: Based on the propagation delay corresponding to the position of each cell, a reverse time shift operation is performed on the measurement time corresponding to the surface temperature of each cell. By adjusting the measurement time of the surface temperature of each cell by backtracking by one of the propagation delays, the backtracking time corresponding to the surface temperature of each cell is obtained; The retrospective moment represents the original moment when the temperature disturbance felt by the cell occurred at the inlet of the flow channel; For the surface temperature of each cell, the difference between the surface temperature of each cell and the historical average value is extracted to obtain the temperature change corresponding to the temperature disturbance; The attenuated amplitude corresponding to each cell position in the attenuation is used as the ratio to the current amplitude. The reciprocal of this ratio is used to perform a scaling operation on the temperature change to obtain the reduction temperature change of each cell. Match the retrospective time with the change in the reduction temperature according to the one-to-one correspondence of the cell positions; Based on the historical average value corresponding to the surface temperature of each cell, the value corresponding to the reduction temperature change is superimposed to obtain the theoretical instantaneous temperature of each cell. The theoretical instantaneous temperature of each battery cell is subtracted from the coolant temperature at each battery cell location one by one to extract the real-time dynamic temperature difference between each battery cell and the coolant flowing through that battery cell location. Based on the combination relationship between the preset frequency range where the frequency amplitude of the main frequency component is located and the preset flow range where the coolant flow rate is located, the combined frequency and flow rate disturbance level of the current operating condition is output. When the combined frequency and flow disturbance level reaches the preset high frequency and high flow operating condition level, the sorting basis for the balanced scheduling is switched from the historical average surface temperature of each cell to the absolute amplitude of the real-time dynamic temperature difference. The cells are sorted according to the absolute amplitude of the real-time dynamic temperature difference, and the heat dissipation power allocation ratio of each cell is calculated according to the sorting position and the preset power mapping relationship. The thermal balance scheduling of each cell is then executed.

2. The lithium-ion battery thermal equalization scheduling method for BMS according to claim 1, characterized in that, The sampling record of the coolant inlet temperature at the inlet of the liquid-cooled module flow channel is obtained, and the main frequency component and current amplitude are analyzed. Simultaneously, the coolant flow rate, surface temperature of each cell, historical average surface temperature of each cell, coolant temperature at each cell location, and the series arrangement position of each cell in the liquid-cooled flow channel and the flow channel length between adjacent cells are obtained, including: By deploying a temperature sensor at the inlet of the liquid cooling module flow channel, the inlet temperature of the coolant is continuously collected according to a preset sampling period, and the sampling record containing timestamps and temperature values ​​is obtained. Perform a Fast Fourier Transform on the sampled records and extract the frequency component with the largest amplitude in the frequency domain distribution as the main frequency component; The amplitude of the dominant frequency component in the spectrum is extracted as the current amplitude; The current coolant flow rate is read using a flow sensor; Real-time measurements of the surface temperature of each battery cell are obtained by temperature sensors placed on the surface of each cell. Retrieve the pre-stored historical average value; The coolant temperature readings at each battery cell location are obtained by using temperature probes embedded in the flow channel. The serial arrangement position is determined according to the physical installation sequence of each cell along the coolant flow direction in the liquid-cooled module.

3. A lithium-ion battery thermal equalization scheduling method for BMS according to claim 1, characterized in that, The analysis of the propagation delay and attenuation of temperature disturbances from the channel inlet to each cell location sequentially along the coolant flow direction, based on the dominant frequency component, the current amplitude, and the coolant flow rate, combined with the series arrangement position of each cell in the liquid cooling channel and the channel length between adjacent cells, includes: The average flow velocity of the coolant in the flow channel is calculated based on the coolant flow rate and the preset cross-sectional area obtained from the liquid cooling system design parameters. The average flow rate is obtained by dividing the coolant flow rate by the preset cross-sectional area; Based on the series arrangement of each battery cell in the liquid cooling channel, the cumulative channel distance from the channel inlet to each battery cell position is sequentially marked along the coolant flow direction; The cumulative flow channel distance is obtained by summing the fixed flow channel length from the inlet to the first cell and the flow channel length between all adjacent cells from the inlet to the first cell segment by segment; Calculate the propagation delay of the temperature disturbance from the channel inlet to each cell location, based on the cumulative channel distance and the average flow velocity. The propagation delay is obtained by dividing the cumulative channel distance by the average flow velocity; According to the order of the series arrangement positions, establish the time delay distribution sequence between the position of each cell and its corresponding propagation time delay; Based on the frequency value of the main frequency component and the cumulative flow channel distance, using an exponential decreasing method with the current amplitude as the initial value and the cumulative flow channel distance as the independent variable, and according to a preset unit distance attenuation ratio and an empirical value based on the thermal conductivity of the material, the attenuated amplitude when the temperature disturbance reaches the position of each cell is calculated segment by segment. The initial value, the cumulative flow channel distance, and the unit distance attenuation ratio are processed according to the preset amplitude attenuation formula to determine the attenuated amplitude. By pairing the propagation delay corresponding to each cell position in the time delay distribution sequence with the attenuated amplitude, a propagation delay and attenuation characteristic describing the temperature disturbance arriving sequentially at each cell position along the coolant flow direction are formed.

4. A lithium-ion battery thermal equalization scheduling method for BMS according to claim 1, characterized in that, The step of subtracting the theoretical instantaneous temperature of each battery cell from the coolant temperature at each battery cell location one by one to extract the real-time dynamic temperature difference between each battery cell and the coolant flowing through that battery cell location includes: Based on the series arrangement of each battery cell in the liquid cooling channel, the theoretical instantaneous temperature of each battery cell and the coolant temperature at each battery cell position are paired one by one according to the same position number to obtain the temperature pairing combination at each battery cell position. For the temperature pairing combination, the theoretical instantaneous temperature of each cell is subtracted from the coolant temperature corresponding to the cell location to obtain the real-time dynamic temperature difference between each cell and the coolant flowing through the cell location.

5. A lithium-ion battery thermal equalization scheduling method for BMS according to claim 1, characterized in that, The step of outputting the joint frequency and flow disturbance level of the current operating condition based on the combination relationship between the preset frequency range of the frequency amplitude of the dominant frequency component and the preset flow range of the coolant flow rate includes: The frequency amplitude of the main frequency component is compared with the preset frequency range boundary to determine the frequency range in which the frequency amplitude is located. At the same time, the flow rate of the coolant is compared with the preset flow rate range boundary to determine the flow rate range in which the coolant flow rate is located. Based on the combination relationship between the preset frequency range and the preset flow range, a preset disturbance level mapping table is queried to obtain the joint disturbance level of frequency and flow under the current operating condition; wherein the disturbance level mapping table is indexed by the pairing data of the preset frequency range and the preset flow range, and the corresponding disturbance level is the output result.

6. A lithium-ion battery thermal equalization scheduling method for BMS according to claim 1, characterized in that, When the combined frequency and flow disturbance level reaches a preset high-frequency, high-flow operating condition level, the sorting criterion for balanced scheduling is switched from the historical average surface temperature of each cell to the absolute amplitude of the real-time dynamic temperature difference. The cells are then sorted according to the absolute amplitude of the real-time dynamic temperature difference. The heat dissipation power allocation ratio of each cell is calculated based on the sorting order and a preset power mapping relationship. Thermal balanced scheduling of each cell is then executed, including: In response to the frequency and flow rate joint disturbance level meeting the preset high frequency and high flow rate operating condition level, a sorting basis update instruction is triggered. According to the sorting basis update instruction, the sorting basis for balanced scheduling is changed from the historical average value to the absolute magnitude of the real-time dynamic temperature difference. The absolute magnitude of the real-time dynamic temperature difference is obtained by taking the absolute value of the real-time dynamic temperature difference; Based on the absolute magnitude of the real-time dynamic temperature difference, the cells are sorted in descending order of value to generate the sorting position of each cell. The ranking order represents the relative ranking of the heat exchange intensity of the battery cell at the corresponding time point; The sorting order is processed by a preset power mapping relationship to obtain the heat dissipation power allocation ratio of each battery cell; The power mapping relationship takes the sorting position as input data and the corresponding heat dissipation power allocation ratio as output result. The thermal balance scheduling of each battery cell is performed according to the heat dissipation power allocation ratio.

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