A thermal management system for recycling battery energy storage units

Abstract

The present application relates to the technical field of lithium ion battery thermal management, and discloses a kind of thermal management system of recycling battery energy storage unit, comprising: battery state acquisition unit obtains the terminal voltage variation sequence of battery module at the initial stage of charge-discharge pulse start;Electrochemical characteristic analysis unit determines the impedance value representing polarization characteristics;Fluid regulating unit obtains the cooling medium delivery time lag and the battery module heat conduction delay time, and determines the internal heat generation peak time according to the impedance value, and then combines the delay time with the delivery time lag to determine the advance action time of regulating valve, the present application constructs the phase alignment mechanism of cooling medium distribution and electrochemical heat generation process, eliminates the physical lag phenomenon existing in traditional temperature feedback regulation, solves the heat generation supervision blind area problem caused by internal resistance dispersion of step utilization battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery thermal management technology, and more specifically, to a thermal management system for a recyclable battery energy storage unit. Background Technology

[0002] Currently, in the operation of large-scale electrochemical energy storage stations, liquid cooling systems are used to maintain the stability of electrochemical reactions. A common approach is to use a cooling pump to drive the medium to flow through the battery module, use a temperature sensor to monitor the surface temperature, and use a controller to adjust the flow rate based on the temperature rise data. In the scenario of cascade utilization, the service history of recycled batteries varies, resulting in discrete distribution of internal resistance in each module. As a multi-layered composite physical entity, lithium-ion batteries have a physical delay in the conduction of internal heat to the surface, which is usually in the range of 30s to 120s. When the recycled battery module encounters a large current charge and discharge pulse, the internal heat generation power jumps. Due to the inertia of thermal conduction, the adjustment mode based on surface temperature feedback cannot complete the cooling distribution in the early stage of heat diffusion, causing heat to accumulate in situ inside the cell.

[0003] Besides the limitations of heat conduction hysteresis at the hardware level, the lag in system control logic is also a bottleneck restricting thermal management efficiency. For example, Chinese invention patent CN114810648B discloses a speed regulation method, heat dissipation device, electronic device and storage medium. It identifies the charging and discharging state and matches the speed regulation algorithm by voltage change rate. This is a passive regulation based on quasi-steady-state electrical signal feedback. It ignores the difference in physical time constant between electrochemical polarization heat generation and heat conduction across the medium. In high internal resistance discrete cascade utilization batteries, there is a phase misalignment between electrical signal fluctuations and the overall thermal field evolution. Existing algorithm switching cannot penetrate the transient evolution process of heat generation inside the cell. It is difficult to offset the regulatory gap formed by the superposition of physical fluid transport lag and heat conduction delay, which limits the service safety and lifespan of recycled batteries.

[0004] Therefore, how to accurately obtain transient heat generation characteristics and achieve zero-phase lag tracking of the cooling flow field on the heat generation process has become the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention provides a thermal management system for a recyclable battery energy storage unit, comprising: The battery status acquisition unit is used to acquire the terminal voltage change sequence of the battery module in the reclaimed battery energy storage unit within a 500ms sampling window after the start of the charge / discharge pulse; The electrochemical characteristic analysis unit, connected to the battery state acquisition unit, is used to calculate the voltage drop rate based on the terminal voltage change sequence and extract the equivalent impedance value characterizing the polarization characteristics based on the voltage drop rate. The liquid cooling circulation branch is equipped with a flow regulating valve; The fluid regulation unit, connected to the electrochemical characteristic analysis unit and the flow regulation valve, is used to obtain the fluid transport time delay of the cooling medium in the liquid cooling circulation branch and the heat conduction delay time from the inside of the battery module to the surface of the battery module. The fluid regulation unit is also used to determine the peak heat generation time inside the battery module based on the equivalent impedance value and to calculate the difference between the heat conduction delay time and the fluid transport time delay to determine the action advance amount. The fluid regulation unit is also used to adjust the opening of the flow regulation valve within the action advance amount before the peak heat generation time arrives, so that the peak cooling power provided by the liquid cooling circulation branch coincides with the peak heat generation power conducted to the surface of the battery module.

[0006] Preferably, the electrochemical characteristic analysis unit extracts the equivalent impedance value through the following steps: Step S21: Calculate the partial derivative of the terminal voltage change sequence with respect to time within a 500ms sampling window to obtain the voltage change rate curve; Step S22: Decouple the voltage change rate curve from the preset ohmic polarization reference value to separate the concentration polarization response component; Step S23: Determine the evolution slope of the equivalent impedance value with respect to the charge and discharge time based on the concentration polarization response component, and use the evolution slope as the feedback gain for adjusting the opening of the flow regulating valve.

[0007] Preferably, the sampling frequency of the battery status acquisition unit is not less than 100Hz, and it is used to collect nonlinear voltage fluctuations in the voltage change sequence at the acquisition end within a time scale of 10ms to 50ms.

[0008] Preferably, the fluid regulation unit calculates the fluid delivery time delay by using the pipe geometry length of the liquid cooling circulation branch and the real-time flow rate of the cooling medium.

[0009] Preferably, the fluid regulation unit is also used to establish an asymmetric flow field distribution rule based on the discrete distribution parameters of the DC internal resistance of each battery module, and to perform differentiated opening compensation for the flow regulation valves on different branches.

[0010] Preferably, the thermal management system further includes a thermal field monitoring unit for acquiring the real-time surface temperature rise rate of the battery module and thereby correcting the impedance model parameters used in the electrochemical feature analysis unit to extract the equivalent impedance value.

[0011] Preferably, the response period of the flow regulating valve is less than 50ms, and its flow regulation amount is monotonically positively correlated with the change in voltage drop rate.

[0012] Preferably, the fluid regulating unit is equipped with a safety threshold detector, which controls the flow regulating valve to switch to the maximum flow opening when the equivalent impedance value exceeds a preset safety threshold.

[0013] Preferably, the fluid regulation unit is also used to obtain the cumulative number of service cycles of each battery module, and to linearly correct the empirical preset value of the heat conduction delay time based on the cumulative number of service cycles.

[0014] The embodiments of the present invention have at least the following beneficial effects: 1. In the thermal management of the battery energy storage unit, a phase offset mechanism is constructed between the cooling medium supply and the electrochemical heat generation process. By real-time acquisition of the transient voltage response slope of each battery module at the beginning of the charge and discharge pulse, the polarization impedance characteristic value is extracted. Combined with the fluid transport time constant, the opening of the corresponding branch proportional regulating valve is pre-adjusted before the heat generation peak is conducted to the battery surface, so that the peak value of the cooling capacity coincides with the peak value of the heat generation power in the time domain, eliminating the physical hysteresis effect in the traditional temperature feedback regulation.

[0015] 2. To address the common problem of internal resistance dispersion in secondary batteries, this invention establishes an asymmetric flow field adjustment mode based on dynamic impedance distribution. The deviation coefficient between the measured DC internal resistance of each branch battery module and the system average level is used as the logical criterion for flow distribution, enabling battery cells with high heat loads to obtain targeted heat dissipation flux compensation, suppressing local heat accumulation caused by thermodynamic non-uniform distribution, and delaying the differential degradation of battery packs caused by asymmetric thermal stress.

[0016] 3. By coupling the electrochemical polarization evolution characteristics with the fluid circulation logic, this invention can predict the temperature rise trend in the initial stage of the internal reaction fluctuation of the cell, and complete the advance supply of cooling medium before the temperature sensing component captures the overall signal, thereby eliminating the thermal monitoring blind spot of the energy storage system under pulsed conditions and improving the operating efficiency of the thermal management system while maintaining a stable electrochemical environment for lithium ions. Attached Figure Description

[0017] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings, in which several embodiments of the invention are illustrated by way of example and not limitation, wherein: Figure 1 This is a schematic diagram illustrating the thermal management system architecture and heat generation-cooling phase alignment principle of the present invention. Figure 2 This is a flowchart of the full-cycle adaptive control logic and model reconstruction of the present invention. Detailed Implementation

[0018] The principles and spirit of the present invention will now be described with reference to several exemplary embodiments in conjunction with the accompanying drawings. It should be understood that these embodiments are provided merely to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0019] A thermal management system for recovering battery energy storage units includes: The battery status acquisition unit is used to acquire the terminal voltage change sequence of the battery module in the reclaimed battery energy storage unit within a 500ms sampling window after the start of the charge / discharge pulse; The electrochemical characteristic analysis unit, connected to the battery state acquisition unit, is used to calculate the voltage drop rate based on the terminal voltage change sequence and extract the equivalent impedance value characterizing the polarization characteristics based on the voltage drop rate. The liquid cooling circulation branch is equipped with a flow regulating valve; The fluid regulation unit, connected to the electrochemical characteristic analysis unit and the flow regulation valve, is used to obtain the fluid transport time delay of the cooling medium in the liquid cooling circulation branch and the heat conduction delay time from the inside of the battery module to the surface of the battery module. The fluid regulation unit is also used to determine the peak heat generation time inside the battery module based on the equivalent impedance value and to calculate the difference between the heat conduction delay time and the fluid transport time delay to determine the action advance amount. The fluid regulation unit is also used to adjust the opening of the flow regulation valve within the action advance amount before the peak heat generation time arrives, so that the peak cooling power provided by the liquid cooling circulation branch coincides with the peak heat generation power conducted to the surface of the battery module.

[0020] Preferably, the electrochemical characteristic analysis unit extracts the equivalent impedance value through the following steps: Step S21: Calculate the partial derivative of the terminal voltage change sequence with respect to time within a 500ms sampling window to obtain the voltage change rate curve; Step S22: Decouple the voltage change rate curve from the preset ohmic polarization reference value to separate the concentration polarization response component; Step S23: Determine the evolution slope of the equivalent impedance value with respect to the charge and discharge time based on the concentration polarization response component, and use the evolution slope as the feedback gain for adjusting the opening of the flow regulating valve.

[0021] Preferably, the sampling frequency of the battery status acquisition unit is not less than 100Hz, and it is used to collect nonlinear voltage fluctuations in the voltage change sequence at the acquisition end within a time scale of 10ms to 50ms.

[0022] Preferably, the fluid regulation unit calculates the fluid delivery time delay by using the pipe geometry length of the liquid cooling circulation branch and the real-time flow rate of the cooling medium.

[0023] Preferably, the fluid regulation unit is also used to establish an asymmetric flow field distribution rule based on the discrete distribution parameters of the DC internal resistance of each battery module, and to perform differentiated opening compensation for the flow regulation valves on different branches.

[0024] Preferably, the thermal management system further includes a thermal field monitoring unit for acquiring the real-time surface temperature rise rate of the battery module and thereby correcting the impedance model parameters used in the electrochemical feature analysis unit to extract the equivalent impedance value.

[0025] Preferably, the response period of the flow regulating valve is less than 50ms, and its flow regulation amount is monotonically positively correlated with the change in voltage drop rate.

[0026] Preferably, the fluid regulating unit is equipped with a safety threshold detector, which controls the flow regulating valve to switch to the maximum flow opening when the equivalent impedance value exceeds a preset safety threshold.

[0027] Preferably, the fluid regulation unit is also used to obtain the cumulative number of service cycles of each battery module, and to linearly correct the empirical preset value of the heat conduction delay time based on the cumulative number of service cycles.

[0028] Example 1: In the operation of a megawatt-level containerized recycled battery energy storage unit deployed at a grid frequency regulation node, continuously receiving high-current charge and discharge pulse commands, the battery modules used in each stage exhibit a physical state with discrete internal resistance distribution. When the charge and discharge pulse is initiated, nonlinear polarization heat generation instantaneously occurs inside the high-internal-resistance battery module. The thermal conduction delay caused by the multi-layer composite physical entity of the lithium-ion battery for the outward diffusion of internal heat is in the range of 30s to 120s. The time misalignment between the electrochemical polarization response speed and the physical heat conduction speed causes the temperature control mechanism relying on surface temperature sensor feedback to fall into a thermal monitoring blind zone, and the cooling medium distribution action lags behind the local transient heat accumulation process inside the battery module. To address the risk of local overheating caused by the aforementioned lag feedback, the battery status acquisition unit acquires the terminal voltage change sequence of the battery module at a sampling frequency of not less than 100Hz within a 500ms sampling window after the start of the charge and discharge pulse. The electrochemical characteristic analysis unit calculates the voltage drop rate based on the terminal voltage change sequence and extracts the equivalent impedance value characterizing the polarization characteristics. The fluid regulation unit receives the equivalent impedance value and simultaneously acquires the fluid transport time delay and heat conduction delay time determined by the geometric length of the liquid cooling circulation branch pipe and the real-time flow rate of the cooling medium. The fluid regulation unit calculates and determines the peak heat generation moment inside the battery module based on the evolution slope of the equivalent impedance value relative to the charging and discharging time. In the specific derivation, the fluid regulation unit multiplies the extracted equivalent impedance value with the square of the real-time charging and discharging current according to Joule's law to obtain the transient ohmic heat generation reference power. The heat generation reference power is combined with the evolution slope to construct a nonlinear parabolic equation of the internal polarization heat generation rate with respect to time. Then, the first derivative of the parabolic equation with respect to time is obtained and set to zero, thereby transforming the electrical parameters of the physical dimension and calculating the time axis coordinate corresponding to the maximum value of the parabola as the peak heat generation moment. The difference between the heat conduction delay time and the fluid transport time delay is calculated to determine the action advance amount, and the control command is output within the action advance amount time window before the arrival of the peak heat generation moment to adjust the opening of the flow regulating valve on the corresponding liquid cooling circulation branch.

[0029] During the aforementioned high-speed regulation, the flow control valve selected in the liquid cooling circulation branch is a two-stage pilot-operated proportional control valve with a voice coil motor direct drive. When it receives the control command, the extremely small pilot valve core can move rapidly within 20ms and establish a pressure difference in the fluid control chamber. The main valve core is opened by relying on the hydraulic pressure of the medium itself. Thus, in terms of overall structural hardware, its primary flow response cycle is compressed within the 50ms boundary limit. At the same time, the multi-stage damping flow channel design absorbs the fluid impact generated by rapid pressure build-up and avoids water hammer damage caused by overshoot. After the flow control valve acts according to the control command, the additional cooling medium reaches the target battery module surface with a delay during fluid delivery. This makes the peak cooling power provided by the liquid cooling circulation branch coincide with the peak heat generation power transferred to the battery module surface after the heat conduction delay time in the time domain. The thermal management system eliminates the thermal monitoring blind spot formed by the superposition of internal resistance dispersion and physical heat conduction lag in the recovered battery energy storage unit by constructing a feedforward counter-current architecture based on the characteristics of electrochemical polarization evolution to drive fluid physical compensation.

[0030] Example 2: The current energy storage test platform is equipped with a megawatt-level bidirectional DC charge-discharge power supply and a liquid-cooled circulation branch with independent flow regulation function. The current step response accuracy of the charge-discharge power supply is 0.1%, and the flow regulation resolution of the liquid-cooled circulation branch is 0.1L / min. The test object is a lithium iron phosphate battery module with a nominal capacity of 280Ah. Before the test starts, Gaussian white noise with a signal-to-noise ratio of 20dB and power frequency interference harmonics with a frequency of 50Hz are injected into the voltage sensing circuit of the battery status acquisition unit to test the system's anti-interference performance under non-ideal industrial electromagnetic environment. The determination of the sampling frequency of the battery status acquisition unit depends on two physical constraints: the integrity of polarization transient feature capture and the data processing load of the electrochemical feature analysis unit. The polarization response caused by the start of the charge-discharge pulse is concentrated in the initial tens of milliseconds. To prevent high-frequency signal aliasing distortion under the Nyquist sampling theorem constraint, the reciprocal of the sampling frequency is required to be less than one-tenth of the polarization response time constant. Based on this rule and combined with the signal bandwidth characteristics, 100Hz is selected as the standard sampling frequency to obtain the terminal voltage change sequence including noise interference.

[0031] After applying a square wave charging pulse with an amplitude of 1C, the battery state acquisition unit outputs a sequence of terminal voltage changes carrying background noise within a 500ms sampling window after the start of the charging / discharging pulse. The electrochemical feature analysis unit uses a low-pass filtering algorithm to filter out power frequency interference harmonics and Gaussian white noise, smooths the terminal voltage change sequence, and then calculates the voltage drop rate. ,in, The terminal voltage and For time, the electrochemical characteristic analysis unit is based on the rate of change of voltage drop. The equivalent impedance value of 1.25 mΩ with a positive evolution slope was extracted. ,in, For impedance and To characterize polarization, the fluid control unit acquires the equivalent impedance value, extracts the difference in equivalent impedance between two adjacent sampling periods, divides it by the corresponding time interval, and precisely quantifies the specific value of its dynamic evolution slope. The system directly uses this evolution slope value as a factor and multiplies it by the preset closed-loop control basic proportional coefficient to calculate the dynamic feedback gain that is linked with the polarization rate. This gain serves as the proportional control term multiplier in the subsequent flow control valve control algorithm, thereby achieving adaptive scaling of the flow opening response amplitude. The fluid control unit acquires the equivalent impedance value. Based on the electrothermal coupling model, it was calculated that the peak heat generation inside the target battery module reaches the battery module surface after a heat conduction delay of 45.0s. The fluid control unit, based on the current pipeline geometry and the real-time flow rate of the cooling medium, obtains a fluid delivery delay of 12.0s. The fluid control unit calculates the difference between the heat conduction delay and the fluid delivery delay, determining a 33.0s advance action. This 33.0s value defines the absolute countdown delay coordinate, with the internal transient heat generation peak as the physical starting point. That is, the system forcibly waits 33.0s before actually triggering the physical action command at the zero moment of polarization heat generation. This waiting mechanism ensures that the remaining... The countdown window for waste heat conduction to reach the surface is reduced to exactly 12.0 seconds, equivalent to the physical transport time of the cooling medium, thus achieving precise offsetting. The fluid control unit outputs a control command 33.0 seconds before the peak heat generation, increasing the opening of the flow control valve on the corresponding liquid cooling circulation branch from the initial 20% to 85%. Addressing the broadening and peak attenuation of the flow pulse waveform caused by frictional resistance and fluid dynamic dispersion during long-distance pipeline transport of the cooling medium, the fluid control unit incorporates one-dimensional pipeline dispersion inverse compensation logic when outputting the action command. Specifically, the fluid control unit calculates fluid dissipation based on the current pipeline Reynolds number. In this operational mechanism, the attenuation rate is not directly calculated using the steady-state hydrodynamic Reynolds number as a scalar for waveform broadening. Instead, it accurately identifies the laminar or turbulent flow characteristics based on the pipeline Reynolds number to retrieve the corresponding Darcy friction coefficient. This coefficient is then correlated with a one-dimensional transient hydrodynamic wave equation containing viscous damping constraints and discretized to infer the true intrinsic loss of the high-frequency flow pulse as it passes through the dispersive medium in the pipeline. When adjusting the flow control valve, the initial opening amplitude is superimposed with an overshoot increment exhibiting time-lead characteristics, for example, increasing it to 90% for instantaneous overflow pre-drive. The overshoot increment is determined by the system's target... The steady-state flow rate is determined by multiplying the dynamic dissipation attenuation factor calculated based on the pipeline friction coefficient and fluid dynamic viscosity. The fluid control unit substitutes the calculated transient high-frequency flow target value into the flow characteristic curve function of the flow control valve, accurately solves the problem, and outputs the corresponding over-opening quantitative command to drive the valve core deflection. This high-frequency pre-gain peak overcomes fluid inertia and dispersion damping, ensuring that after the flow pulse has undergone physical transport in a long pipeline for tens of seconds, the actual flow envelope reaching the surface of the battery module is smoothly attenuated to the required precise cooling power peak, thereby achieving strict alignment of the medium flow rate with the heat generation peak in both space and time.

[0032] The experiment established a control group with a surface temperature feedback-triggered cooling mechanism and a partially missing control group lacking a fluid delivery time delay compensation stage. Experimental groups with internal resistances of 0.5 mΩ and 2.5 mΩ were also set up to test the numerical boundary and heat offset effect of the feedforward regulation mechanism. Test data showed that the surface temperature of the control group rose by 4.8°C within the first 60.0 seconds after pulse activation, triggering a high-temperature alarm. The partially missing control group experienced a 3.5°C temperature overshoot fluctuation due to the flow control valve's failure to counteract the physical fluid inertia. In the test group, the increased cooling medium supplied by the flow control valve transcended the fluid transport time lag, coinciding with the arrival of the peak heat generation at the surface. Under internal resistance conditions of 0.5mΩ and 2.5mΩ, the maximum temperature rise of the module surface was limited to 1.2℃ and 1.4℃, respectively. Synchronous test data reflected the nonlinear thermal effect at the solid-liquid interface. After the flow control valve opening exceeded 95%, the cooling power increment stagnated due to the thermal saturation limitation of the battery module surface boundary layer, and the fluid pumping energy consumption increased exponentially. This was based on the action lead and equivalent impedance value. The calculated 85% opening adjustment command constitutes a working window that balances the heat offset demand and the system energy consumption boundary. Multidimensional gradient data confirms that the equivalent impedance value extracted by the battery state acquisition unit and the action lead calculated by the fluid regulation unit are causally related. The two have a synergistic effect in eliminating the dual obstacles of physical heat conduction lag and fluid transport time lag. The thermal management system changes the feedback mode that relies on passive response to surface temperature. It reconstructs the allocation benchmark of cooling resources by calculating the polarization heat generation evolution path. The fluid physical compensation mechanism suppresses and recovers the discrete nonlinear polarization heat generation inside the battery energy storage unit, transforming it into a predictable and quantifiable controlled state.

[0033] Example 3: The megawatt-level reclaimed battery energy storage unit at the current grid frequency regulation node continuously receives step charge / discharge pulse commands. The internal resistance of the battery module causes a nonlinear polarization effect, resulting in a transient sharp drop in the terminal voltage. Within a fixed sampling window of 500ms after the charge / discharge pulse start signal, the battery status acquisition unit continuously acquires the terminal voltage sequence and the corresponding charge / discharge current sequence at a sampling frequency of 100Hz. The electrochemical feature analysis unit synchronously receives the terminal voltage sequence and the charge / discharge current sequence, extracts the voltage difference between two adjacent sampling points in the terminal voltage sequence, divides the voltage difference by the corresponding sampling time interval, and calculates the output voltage drop rate. ,in, Terminal voltage, For time; a first-order equivalent circuit model data decoupling procedure is established to analyze the pure resistive ohmic voltage drop and the RC network polarization voltage drop in the cell pulse response voltage. The electrochemical feature analysis unit reads the absolute value of the voltage drop within the initial 20-millisecond sampling window after pulse start and divides it by the corresponding charge / discharge current amplitude to generate the ohmic polarization reference value. The concentration polarization response component is separated by subtracting the product of the corresponding charge / discharge current sequence and the ohmic polarization reference value from the terminal voltage sequence. The electrochemical feature analysis unit selects the voltage drop change rate. The moment when the peak value is reached is taken as the dominant point of polarization impedance. The transient drop in terminal voltage corresponding to the dominant point is extracted. The transient drop in terminal voltage is divided by the current amplitude in the charge and discharge current sequence to calculate the equivalent impedance value characterizing the polarization characteristics. ,in, For impedance, Characterizing polarization, the above computational link transforms electrochemical polarization characteristics into quantitative parameters calculated based on real-time physical quantity quotients.

[0034] The fluid control unit obtains the equivalent impedance value. Then, the physical thickness parameters of the battery module and the intrinsic thermal diffusivity of the cell material are extracted from the preset memory. The square of the physical thickness parameter of the battery module is divided by the intrinsic thermal diffusivity of the cell material to calculate and determine the heat conduction delay time. In order to introduce the electrochemical polarization characteristics into the time domain determination, the fluid regulation unit performs nonlinear weighting correction on the heat conduction delay time obtained in the preliminary calculation based on the obtained equivalent impedance value. Specifically, through the preset polarization-thermal relaxation empirical relationship, the hysteresis correction coefficient, which is mapped to characterize the surface polarization intensity, is multiplied by the heat conduction delay time initially extracted above, thereby outputting the actual heat conduction delay time dynamically scaled according to the current polarization state of the battery. The fluid regulation unit simultaneously extracts the total length parameter of the liquid cooling circulation branch, reads the real-time volumetric flow rate of the cooling medium fed back by the flow sensor installed at the end of the liquid cooling circulation branch, calculates the real-time flow velocity of the cooling medium in combination with the cross-sectional area of ​​the pipe, and divides the total length parameter of the pipe by the real-time flow velocity of the cooling medium to calculate the fluid delivery time delay. The fluid regulation unit compares the heat conduction delay time with the actual thermal diffusivity of the cell material. The magnitude of the fluid transport time delay is determined by subtracting the fluid transport time delay from the heat conduction delay, provided the difference is greater than zero, to output the action advance. A control command mapping procedure is established based on Joule's law and the principle of convective heat transfer. The fluid regulating unit calculates the transient heat generation power by multiplying the equivalent impedance value by the square of the current amplitude in the charging / discharging current sequence. Combining the specific heat capacity constant of the cooling medium and the preset inlet / outlet water control temperature difference, the transient heat generation power is divided by the product of the specific heat capacity constant and the control temperature difference to convert it into the target volumetric flow rate. The fluid regulating unit calls the preset liquid cooling circulation branch flow resistance characteristic curve to obtain the expected steady-state flow velocity corresponding to the target volumetric flow rate, eliminating the interference of dynamic flow velocity fluctuations caused by valve opening changes. The total pipeline length parameter is divided by the expected steady-state flow velocity to recalculate the dynamic fluid transport time delay and correct the action advance. The fluid regulating unit determines the peak heat generation time by adding the heat conduction delay time to the start time of the charging / discharging pulse. The time node determined by subtracting the action advance from the peak heat generation time is used to output a control command containing the target valve opening data, adjusting the flow regulating valve on the liquid cooling circulation branch.

[0035] The test platform incorporates calculation logic for battery modules with internal resistance gradients of 0.5mΩ, 1.5mΩ, and 2.5mΩ, and the corresponding output action lead time varies with the equivalent impedance value. The increase in the peak heat generation time and the corresponding earlier timing show an increasing trend. In this calculation logic, the specific operation mode of the asymmetric flow field distribution rule is as follows: the fluid regulation unit calculates in real time the ratio of the DC internal resistance of each individual battery module to the average internal resistance of the energy storage unit, which is used as the bias coefficient for the distribution flow field. The system's reference cooling volume flow rate is multiplied by this bias coefficient to obtain the basic expected flow rate of each branch. At the same time, for high-impedance modules with a bias coefficient greater than 1.5, an exponential flow compensation term proportional to the equivalent impedance difference is added. When this nonlinear flow field bias is executed, the system extracts the difference between the measured equivalent impedance value of the high-impedance battery module and the average equivalent impedance value of the energy storage unit as a dynamic variable. This difference is multiplied by a set scaling coefficient and used as the exponent of the natural constant e to calculate a compensation multiplier with nonlinear amplification properties and applied to the corresponding branch. Based on the expected flow rate of the path, the final physical control opening of the action is obtained; finally, the differentiated target flow rate values ​​are integrated, and control commands are issued to the flow regulating valves of the corresponding branches to execute the determined opening deflection action. The flow regulating valves increase the distribution of cooling medium according to the control commands. The cooling medium crosses the fluid transport time delay and coincides with the heat exchange power when it arrives at the surface at the peak of heat generation, so that the maximum temperature rise of the battery module surface under the internal resistance conditions of 0.5mΩ, 1.5mΩ and 2.5mΩ is limited to the range of 1.2℃, 1.3℃ and 1.4℃ respectively; the thermal management system relies on the quantitative mapping relationship between the terminal voltage sequence analysis and the physical space time delay calculation to replace the preset static delay compensation method, aligning the cooling resource allocation benchmark with the polarization heat generation evolution path on the time axis, forming a control structure for the heat dissipation characteristics of the cascaded battery module.

[0036] Example 4: When a megawatt-level recycled battery energy storage unit at a grid frequency regulation node is connected to a new batch of cascaded battery modules, the differences in aging states among the batches of batteries cause parameter mismatch in the pre-set electrothermal coupling model. To establish a calculation benchmark that matches the physical properties of the current batch, the fluid regulation unit initiates a pre-baseline calibration before the system is connected to the grid. The battery status acquisition unit applies a step probe pulse with an amplitude of 0.5C to the target battery module and simultaneously acquires the transient voltage drop sequence under the excitation of the step probe pulse and the time-series temperature rise curve of the corresponding surface temperature. The electrochemical characteristic analysis unit calculates the terminal voltage. The ratio of the transient drop sequence to the step detection pulse current amplitude is used to output the reference polarization impedance. The electrochemical feature analysis unit extracts the time node when the surface temperature reaches the steady-state peak based on the time-series temperature rise curve, and calculates the thermal conduction delay time of the specific batch of battery modules by combining the square value of the physical thickness parameter of the battery module. The system repeats the above step detection pulse excitation and calculation steps for different states of charge and temperature boundaries to construct an offline mapping relationship matrix containing multiple sets of reference polarization impedances and corresponding thermal conduction delay times. The fluid regulation unit writes the offline mapping relationship matrix into the preset memory.

[0037] In actual charging and discharging operation, the fluid regulation unit calls the offline mapping relationship matrix in the preset memory; the fluid regulation unit receives the equivalent impedance value calculated and output by the electrochemical characteristic analysis unit in real time, and uses a linear interpolation algorithm to address and match the corresponding dynamic heat conduction delay time in the offline mapping relationship matrix; the fluid regulation unit synchronously reads the total length parameter of the liquid cooling circulation branch and the real-time flow rate of the cooling medium fed back by the flow sensor, calculates the quotient of the total length parameter of the pipeline and the real-time flow rate of the cooling medium, and obtains the fluid delivery time delay; the fluid regulation unit calculates the difference between the dynamic heat conduction delay time and the fluid delivery time delay, and outputs the action advance; the fluid regulation unit outputs control commands according to the action advance to adjust the flow regulating valve on the corresponding liquid cooling circulation branch; the thermal management system, through the combination of pre-baseline calibration and online data addressing, transforms the unknown thermophysical properties of non-standard batch cascade utilization batteries into a pre-determined numerical matrix, eliminating the physical calculation deviation caused by the mismatch of underlying model parameters.

[0038] Example 5: In the operating condition where the recycled battery energy storage unit is undergoing charge-discharge cycles, causing the intrinsic thermal diffusivity of the cell material to decay and resulting in deviations in the offline mapping matrix, the fluid regulation unit presets a sliding time window, counts the cumulative charge-discharge amount of the target battery module within the sliding time window, compares the cumulative charge-discharge amount with a set decay judgment threshold, and outputs a benchmark update command if the cumulative charge-discharge amount exceeds the decay judgment threshold. The battery status acquisition unit receives the benchmark update command and applies a verification pulse with an amplitude of 0.5C to the target battery module during the power interaction gap, simultaneously acquiring the verification pulse. The transient voltage drop sequence under excitation and the time-series temperature rise curve of the surface temperature, the attenuation judgment threshold relied upon in the above trigger judgment logic, are determined in advance through offline accelerated aging calorimetric experiments on recycled batteries with the same service history. The system establishes an attenuation scatter plot model with the cumulative ampere-hour throughput as the abscissa and the intrinsic thermal diffusivity of the material as the ordinate. The partial derivative is obtained by expanding the first-order Taylor series, and the critical cumulative charge-discharge capacity value corresponding to the thermal diffusivity reaching the preset tolerance limit (e.g., 5% of the base value) is calculated in reverse. This is used as a rigorous and quantitative threshold benchmark input to the system.

[0039] The electrochemical characteristic analysis unit calculates the quotient of the transient voltage drop sequence and the amplitude of the verification pulse current to obtain the decaying polarization impedance. It extracts new time nodes in the time-series temperature rise curve where the surface temperature undergoes a sudden change. The time difference between these new time nodes and the pulse start time is determined as the decaying heat conduction delay time. The fluid control unit reads the offline mapping matrix, locates the initial node where the reference polarization impedance and the decaying polarization impedance are equal, and calculates the quotient of the decaying heat conduction delay time and the corresponding heat conduction delay time of the initial node to generate the time decay factor. ,in, This is the proportionality coefficient. Characterizing the decay variable, the fluid control unit maps the heat conduction delay time and time decay factor of each node in the offline mapping relationship matrix. The components are multiplied sequentially to generate a dynamic mapping matrix, which is then written into the preset memory. The thermal management system uses this dynamic mapping matrix to calculate the advance of action to control the flow regulating valve and compensate for the physical property offset accumulated over the service life.

[0040] The above description is only a few preferred embodiments of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present invention is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, technical solutions formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present invention.

Claims

1. A thermal management system for a recycled battery energy storage unit, characterized in that, include: The battery status acquisition unit is used to acquire the terminal voltage change sequence of the battery module in the reclaimed battery energy storage unit within a 500ms sampling window after the start of the charge / discharge pulse; The electrochemical characteristic analysis unit, connected to the battery state acquisition unit, is used to calculate the voltage drop rate based on the terminal voltage change sequence and extract the equivalent impedance value characterizing the polarization characteristics based on the voltage drop rate. The liquid cooling circulation branch is equipped with a flow regulating valve; The fluid regulation unit, connected to the electrochemical characteristic analysis unit and the flow regulation valve, is used to obtain the fluid transport time delay of the cooling medium in the liquid cooling circulation branch and the heat conduction delay time from the inside of the battery module to the surface of the battery module. The fluid regulation unit is also used to determine the peak heat generation time inside the battery module based on the equivalent impedance value and to calculate the difference between the heat conduction delay time and the fluid transport time delay to determine the action advance amount. The fluid regulation unit is also used to adjust the opening of the flow regulation valve within the action advance amount before the peak heat generation time arrives, so that the peak cooling power provided by the liquid cooling circulation branch coincides with the peak heat generation power conducted to the surface of the battery module.

2. The thermal management system for a recyclable battery energy storage unit according to claim 1, characterized in that, The electrochemical characteristic analysis unit extracts the equivalent impedance value through the following steps: Step S21: Calculate the partial derivative of the terminal voltage change sequence with respect to time within a 500ms sampling window to obtain the voltage change rate curve; Step S22: Decouple the voltage change rate curve from the preset ohmic polarization reference value to separate the concentration polarization response component; Step S23: Determine the evolution slope of the equivalent impedance value with respect to the charge and discharge time based on the concentration polarization response component, and use the evolution slope as the feedback gain for adjusting the opening of the flow regulating valve.

3. The thermal management system for a recyclable battery energy storage unit according to claim 1, characterized in that, The sampling frequency of the battery status acquisition unit is no less than 100Hz, which is used to collect nonlinear voltage fluctuations in the voltage change sequence at the acquisition end within a time scale of 10ms to 50ms.

4. The thermal management system for a recyclable battery energy storage unit according to claim 1, characterized in that, The fluid regulation unit calculates the fluid delivery time delay by taking into account the geometric length of the liquid cooling circulation branch and the real-time flow rate of the cooling medium.

5. The thermal management system for a recyclable battery energy storage unit according to claim 1, characterized in that, The fluid control unit is also used to establish asymmetric flow field distribution rules based on the discrete distribution parameters of the DC internal resistance of each battery module, and to perform differentiated opening compensation for the flow control valves on different branches.

6. The thermal management system for a regenerating battery energy storage unit according to claim 1, characterized in that, The thermal management system also includes a thermal field monitoring unit, which is used to acquire the real-time surface temperature rise rate of the battery module and correct the impedance model parameters used in the electrochemical feature analysis unit to extract the equivalent impedance value accordingly.

7. The thermal management system for a recyclable battery energy storage unit according to claim 1, characterized in that, The response period of the flow regulating valve is less than 50ms, and its flow regulation amount is monotonically positively correlated with the change in voltage drop rate.

8. The thermal management system for a recyclable battery energy storage unit according to claim 1, characterized in that, The fluid control unit is equipped with a safety threshold detector, which controls the flow control valve to switch to the maximum flow opening when the equivalent impedance value exceeds the preset safety threshold.

9. The thermal management system for a recyclable battery energy storage unit according to claim 1, characterized in that, The fluid conditioning unit is also used to obtain the cumulative service cycle count of each battery module and to linearly correct the empirical preset value of the heat conduction delay time based on the cumulative service cycle count.

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