A deep groove wrapped lithium battery liquid cooling heat dissipation system based on fuzzy PID control

Abstract

The application discloses a deep-groove wrapped lithium battery liquid cooling heat dissipation system based on fuzzy PID control and relates to the technical field of battery thermal management. The system comprises a battery module unit, a liquid cooling circulation loop, a data acquisition unit and a main controller. The battery module unit is integrated with square lithium batteries and deep-groove wrapped heat exchangers. The liquid cooling circulation loop is used for realizing external energy transfer. The data acquisition unit is used for collecting temperature signals reflecting the thermal state of the square lithium batteries in real time. The main controller performs logical reasoning on the temperature signals through a fuzzy PID control program, generates a pulse width modulation (PWM) signal, and adjusts the cooling liquid flow rate of a variable frequency water pump and the heat exchange intensity of a radiator assembly. Through the deep cooperation of the deep-groove wrapped heat exchange structure and the fuzzy PID control program, the heat exchange efficiency, temperature uniformity and temperature control precision of the lithium battery module are greatly improved, the optimal balance of heat dissipation energy efficiency is realized, and the operation reliability, safety performance and cycle life of the battery system are enhanced.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management technology, and in particular to a deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control. Background Technology

[0002] With the profound transformation of the global energy structure and the booming development of new energy vehicles and large-scale energy storage systems, lithium-ion batteries, as the core energy carrier, have become a key factor restricting the continuous upgrading of related industries due to their safety, cycle life, and power output characteristics. At the electrochemical level, the performance of lithium-ion batteries is strongly coupled with their operating temperature, which is generally considered to be between 25°C and 40°C. However, in actual operating conditions, especially under high-rate charge / discharge or extreme environmental conditions, large-scale square battery modules composed of dozens or even hundreds of cells can generate intense heat. If this heat cannot be dissipated in a timely and effective manner, it will not only lead to an imbalance in the internal chemical reaction rate of the battery and shorten its lifespan, but may also trigger a chain reaction of safety issues due to localized thermal runaway. Therefore, building an efficient, stable, and intelligent battery thermal management system (BTMS) has become a current research focus in the field of electrochemical energy.

[0003] Within the existing technological framework, liquid cooling solutions, due to their higher heat transfer coefficient and specific heat capacity, have gradually replaced air cooling as the mainstream choice for large power battery packs. Traditional liquid cooling solutions typically employ bottom or side liquid cooling plates, exchanging heat by attaching the cooling plates to the outer surface of the battery module. Furthermore, existing liquid cooling plates often feature serpentine flow channels or parallel direct-flow channels. Driven by a circulating pump, the coolant flows through these channels, dissipating heat generated by the battery cells through conduction and convection. This design is reasonable for handling low energy density heat dissipation, and its simple structure makes it easy to integrate.

[0004] However, with the continuous increase in the capacity of individual battery cells and the increasing integration density of battery packs, the inherent limitations of the aforementioned existing technologies at the principle level have become apparent, making it difficult to meet the demands of modern operating conditions. Firstly, in terms of physical space, traditional bottom or side cooling plates can only achieve point-to-point or face-to-face contact with the battery surface. This typical two-dimensional cooling ignores the thermal resistance distribution of large square batteries in the height direction. Due to the anisotropic thermal conductivity of the battery materials themselves, the path of heat transfer from the center of the cell to the bottom is relatively long, resulting in significant temperature differences between the top and bottom of the battery, and between the core and the outer skin. Especially during high-rate discharge, this thermal gradient is further exacerbated, worsening the temperature uniformity within the module and severely affecting the consistency maintenance of the cells. Secondly, from a fluid dynamics perspective, in the heat exchange process of traditional serpentine or direct-flow channels, the coolant temperature increases with the increase in flow path, resulting in an inherent temperature gradient between the outlet and inlet ends. This means that battery cells far from the center of the channel or located downstream cannot obtain equal cooling gains.

[0005] Furthermore, due to the significant thermal inertia of battery modules, there is a substantial time delay between the start-up of the cooling system and the change in the core battery temperature. Existing control schemes mostly employ traditional fixed-parameter PID algorithms or simple on / off / constant-speed control modes. Fixed-parameter PID control often exhibits a trade-off between response speed and stability when dealing with sudden load changes (such as severe vehicle acceleration or braking): if a rapid response is prioritized by increasing the proportional gain, severe temperature overshoot can easily occur due to thermal hysteresis, leading to overcooling of the battery and excessive energy consumption; if stability is prioritized by reducing the gain, the system will react slowly to surges in heat load and be unable to suppress temperature rise in time.

[0006] In summary, existing liquid cooling technologies suffer from heat transfer blind spots in structural layout, uneven heat transfer in flow channel design, and difficulty in overcoming dynamic response failures caused by nonlinear thermal hysteresis in control strategies. How to achieve comprehensive heat transfer around the battery cell through in-depth structural innovation, combined with advanced adaptive intelligent control algorithms, to achieve precise temperature control and energy efficiency balance under complex and variable operating conditions, has become a key challenge and an urgent technical problem for those skilled in the art. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control. Through the deep synergy between the deep-groove enclosed heat exchange structure and the fuzzy PID control program, the heat exchange efficiency, temperature uniformity, and temperature control accuracy of the lithium battery module are significantly improved. At the same time, the optimal balance of heat dissipation efficiency is achieved, enhancing the operational reliability, safety performance, and cycle life of the battery system.

[0008] This invention provides a deep-groove enclosed lithium battery liquid cooling heat dissipation system based on fuzzy PID control. The system includes a battery module unit, a liquid cooling circulation loop, a data acquisition unit, and a main controller. The battery module unit integrates several square lithium battery cells and a deep-groove enclosed heat exchanger. The liquid cooling circulation loop connects the deep-groove enclosed heat exchanger, liquid storage tank, variable frequency water pump and radiator assembly through pipelines to form a closed fluid circulation path for realizing external energy transfer. The data acquisition unit is distributed at multiple preset positions in the battery module unit and is used to acquire temperature signals that reflect the thermal state of the square lithium battery in real time. The main controller performs logical reasoning on the temperature signal collected by the data acquisition unit by executing a fuzzy PID control program, and generates a pulse width modulation (PWM) signal to adjust the coolant flow rate of the variable frequency water pump and the heat exchange intensity of the radiator assembly. The deep-groove enclosed heat exchanger adopts an integrated molding structure with a matrix arrangement of deep heat exchange grooves inside for placing square lithium batteries. The deep-groove enclosed heat exchanger also has a hollowed-out liquid cooling structure. The hollowed-out liquid cooling structure includes cooling liquid channels extending along the four side walls and bottom of the deep heat exchange grooves, which are used to form a fully enclosed heat exchange interface on the outer periphery and bottom of the square lithium batteries.

[0009] Preferably, the deep-groove enclosed heat exchanger comprises: The deep-groove enclosed heat exchanger is manufactured by controlled atmosphere brazing process and includes 60 independent heat exchange deep grooves. The inner wall dimensions of each independent heat exchange deep groove are precisely tolerant to the outer dimensions of the square lithium battery. The deep-groove enclosed heat exchanger is a hollowed-out liquid-cooled structure with a built-in flat microchannel liquid-cooling network. The flat microchannel liquid-cooling network introduces coolant through an inlet manifold located on the first side of the deep-groove enclosed heat exchanger. The flat microchannels evenly guide the coolant to the branch channels surrounding and at the bottom of each independent heat exchange deep groove. The coolant flows upward from the bottom in the flat microchannels and collects at the outlet manifold located on the second side of the deep-groove enclosed heat exchanger. An alumina-based silicone thermal interface material is uniformly filled in the gap between the square lithium battery and the inner wall of the independent heat exchange deep groove.

[0010] Preferably, the deep-groove enclosed heat exchanger further includes: The flat microchannel of the deep-groove enclosed heat exchanger adopts a non-uniform cross-section design. In the 1 / 3 region near the liquid inlet, the internal width of the flat microchannel narrows to increase the local flow velocity of the fluid using Bernoulli's principle, thereby enhancing the Reynolds number and improving the convective heat transfer coefficient in the region with a small inlet temperature difference. In the middle section of the channel and the liquid outlet region, the channel width returns to 2.5 mm, and staggered turbulent micro-pillars with a height of 0.5 mm are set on the wall of the flat microchannel to induce local turbulence in the fluid.

[0011] Preferably, the liquid cooling circulation loop includes: The liquid cooling circulation loop connects the deep-groove enclosed heat exchanger, liquid storage tank, variable frequency water pump and radiator assembly in sequence through high-pressure resistant rubber pipes, forming a closed fluid circulation path; The variable frequency water pump is a DC brushless electronic water pump with a speed control interface that supports PWM signal speed control. It has an integrated Hall sensor for real-time feedback of the speed status and receives the first PWM signal output by the main controller to achieve stepless adjustment of the coolant flow rate. The liquid storage tank is located on the upstream suction side of the variable frequency water pump. It is equipped with a labyrinth baffle structure inside to efficiently capture tiny air bubbles in the circulation system, prevent water pump cavitation, and buffer the pressure fluctuation of the coolant and accommodate the thermal expansion volume of the coolant. The radiator assembly includes a radiator body, a first cooling fan, and a second cooling fan; wherein, the radiator body enhances the secondary heat exchange efficiency through heat pipes; the first cooling fan and the second cooling fan are started, stopped, and speed adjusted in stages according to the control signal of the main controller.

[0012] Preferably, the data acquisition unit includes: The data acquisition unit includes 12 NTC thermistor sensors; the NTC thermistor sensors are fixed to the preset monitoring points of the battery module unit by thermally conductive adhesive; among them, 4 are deployed near the liquid inlet manifold area, 4 are deployed in the physical geometric center area of ​​the battery module, and 4 are deployed near the liquid outlet manifold area, to cover the hot spot area and the average temperature representative area of ​​the battery module. The temperature signals from each NTC thermistor sensor are connected to the 12-bit multi-channel analog-to-digital converter module built into the main controller via shielded twisted-pair cables. The main controller first uses a preprocessing algorithm that combines median filtering and arithmetic mean filtering to filter out electromagnetic interference in the vehicle environment. Then, it calculates the real-time average temperature of the battery module using a weighted average algorithm, and obtains the real-time maximum temperature of the battery module by comparing extreme values.

[0013] Preferably, the fuzzy PID control program includes: S1. Set the target preset temperature of the battery module, calculate the temperature deviation between the target preset temperature and the real-time average temperature in real time, and calculate the rate of change of the temperature deviation. S2. Map the temperature deviation and the rate of change of temperature deviation to a preset fuzzy set universe of discourse, wherein the universe of discourse for temperature deviation is set to [-3℃, +3℃], and the universe of discourse for the rate of change of temperature deviation is set to [-1℃ / s, +1℃ / s]; and divide the temperature deviation and the rate of change of temperature deviation into 7 fuzzy levels. S3. Based on the preset fuzzy control rule table, perform logical reasoning on the input fuzzy quantity and output the correction amount of the PID parameter; S4. Add the correction values ​​of the PID parameters to the preset base PID parameters respectively. , , The above provides the optimal PID parameters for the current operating conditions. S5. Linearly map the control output to two independent PWM drive signals.

[0014] Preferably, step S2 further includes: in the selection of membership functions, for the deviation range of temperature deviation within the range of [-0.5℃, 0.5℃], a triangular membership function is used to enhance the steady-state control accuracy of the system; for the deviation range of temperature deviation within the range of [-3℃, -2℃] or [2℃, 3℃], a trapezoidal membership function is used to ensure the rapid response capability of the system.

[0015] Preferably, the logical reasoning includes: When the temperature deviation is positive (PB), increase the positive proportional coefficient correction amount. At the same time, reduce the correction amount of the integral coefficient. ; When the temperature deviation is within a moderate range and the rate of change of the deviation is in the same direction as the temperature deviation, maintain the positive proportionality correction factor. At the same time, a correction factor for the differential coefficients is introduced. ; When the temperature deviation gradually approaches zero and the rate of change of deviation shows an overshoot trend, increase the differential coefficient correction amount. At the same time, reduce the correction amount of the proportional coefficient. Increase the dynamic damping of the system to allow the temperature to converge smoothly to the target value; When both the temperature deviation and the rate of change of deviation are at zero (ZO), increase the integral coefficient correction amount. The residual steady error is eliminated through integral action.

[0016] Preferably, the two independent PWM drive signals include: The first PWM signal has its duty cycle given in real time by the control output of the fuzzy PID algorithm, directly acting on the speed control interface of the variable frequency water pump. By adjusting the duty cycle, stepless control of the coolant flow rate is achieved. When the cell heat load is lower than the heat load threshold, the water pump operates in the range of 20% to 30% of the rated speed. When a rapid temperature rise caused by high-rate discharge is detected, the water pump operation is increased to 80% to 100%. The second PWM signal is used to control the fan speed of the heat sink assembly. The main controller executes a graded control strategy based on the real-time maximum temperature: when the real-time maximum temperature exceeds the first preset threshold, the first cooling fan is turned on and stepless speed regulation is performed through the PWM signal; when the real-time maximum temperature exceeds the second preset threshold, the second cooling fan is started simultaneously until the maximum temperature of the battery module is lower than the safety threshold, so as to achieve dynamic matching between heat dissipation intensity and heat load.

[0017] Compared with the prior art, the present invention has significant technical advantages: 1. By using a matrix-style flat microfluidic liquid cooling network, independent heat exchange branches are set around the perimeter and bottom of each cell. Combined with the uniform flow layout of the coolant from bottom to top, the flow rate of each cell's heat exchange interface is ensured to be evenly distributed. At the same time, through the synergistic design of non-uniform cross-section flow channels and staggered turbulence micropillars, the Reynolds number of the fluid is increased and the convective heat transfer coefficient is enhanced by narrowing the flow channel at the inlet section. In the middle and rear sections, the turbulence micropillars disrupt the fluid boundary layer and induce local turbulence. This effectively compensates for the decrease in heat transfer driving force caused by the temperature rise of the coolant along the flow path, eliminates the inherent temperature rise gradient at the inlet and outlet of the flow channel, and enables cells in different positions and upstream and downstream areas within the battery module to obtain equal cooling gains, avoiding local cell overheating failure.

[0018] 2. A fuzzy PID control program is adopted, taking the battery module temperature deviation and deviation change rate as input. Based on the operating condition characteristics, the PID parameters are adaptively corrected in real time. Combined with the interval membership function design, it takes into account the ability to suppress rapid temperature rise under large deviation conditions and the steady-state temperature control accuracy under small deviation conditions. Through the differential lead adjustment logic, the thermal hysteresis effect caused by the thermal inertia of the battery module is effectively overcome, significantly suppressing temperature overshoot, avoiding battery overcooling, and accurately maintaining the battery in the optimal operating temperature range. At the same time, through the coordinated control of stepless speed regulation of the variable frequency water pump and the staged start and stop of the cooling fan, the dynamic matching of heat dissipation intensity and cell heat load is achieved, realizing the optimal balance between temperature control performance and system energy efficiency.

[0019] 3. The upstream labyrinthine liquid storage tank design effectively captures air bubbles in the circulation system and prevents water pump cavitation. At the same time, it buffers pressure fluctuations, accommodates the thermal expansion of coolant, and improves the long-term operational stability of the circulation loop. Through a multi-point distributed temperature acquisition layout, it comprehensively covers the low-temperature zone, high-temperature risk zone, and outlet area of ​​the battery module. Combined with a composite preprocessing algorithm of median filtering and arithmetic mean filtering, it effectively shields the interference of the complex electromagnetic environment on the vehicle, ensuring the accuracy and representativeness of temperature acquisition. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall architecture of the system described in this invention.

[0021] Figure 2 This is a logic block diagram of the fuzzy PID control program in this invention.

[0022] Figure 3 This is a schematic diagram of the overall hardware structure of the system described in this invention.

[0023] Figure 4 This is a three-dimensional exploded structural diagram of the battery module and liquid cooling circulation loop in this invention.

[0024] Figure 5 This is a logic block diagram of the fuzzy PID control strategy in this invention.

[0025] Figure 6 This is the fuzzy control rule diagram in this invention. Detailed Implementation

[0026] 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention. It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0027] Example 1 Please see Figures 1-6 The present invention provides a deep-groove enclosed lithium battery liquid cooling heat dissipation system based on fuzzy PID control. The system includes a battery module unit, a liquid cooling circulation loop, a data acquisition unit and a main controller. The battery module unit, as a heat source carrier and heat exchange core, integrates several square lithium battery cells and a deep groove enclosed heat exchanger. The liquid cooling circulation loop connects the deep-groove enclosed heat exchanger, liquid storage tank, variable frequency water pump and radiator assembly through pipelines to form a closed fluid circulation path for realizing external energy transfer. The data acquisition unit is distributed at multiple preset positions in the battery module unit and is used to acquire temperature signals that reflect the thermal state of the square lithium battery in real time. The main controller performs logical reasoning on the temperature signal collected by the data acquisition unit by executing a fuzzy PID control program, and generates a pulse width modulation (PWM) signal to adjust the coolant flow rate of the variable frequency water pump and the heat exchange intensity of the radiator assembly. The deep-groove enclosed heat exchanger adopts an integrated molding structure with a matrix arrangement of deep heat exchange grooves inside for placing square lithium batteries. The deep-groove enclosed heat exchanger also has a hollowed-out liquid cooling structure. The hollowed-out liquid cooling structure includes cooling liquid channels extending along the four side walls and bottom of the deep heat exchange grooves, which are used to form a fully enclosed heat exchange interface on the outer periphery and bottom of the square lithium batteries.

[0028] Regarding the physical structure of the battery module unit, this embodiment uses 60 standard square lithium batteries, each with a nominal capacity of 100Ah and a rated voltage of 3.7V. To meet system-level heat dissipation requirements, the 60 square lithium batteries are arranged in a matrix configuration of 3 rows × 20 columns to form a standardized battery module. Each battery module also includes a deep-groove enclosed heat exchanger. This deep-groove enclosed heat exchanger adopts an integrated molding structure, specifically using 3003 series aluminum alloy material, manufactured through controlled atmosphere brazing (CAB) technology. Its measured thermal conductivity is no less than 200 W / (m·K), ensuring the sealing of the internal flow channels and the mechanical strength of the overall structure. The deep-groove enclosed heat exchanger includes 60 independent heat exchange grooves. The inner wall dimensions of each independent heat exchange groove are precisely tolerant to the outer dimensions of the square lithium battery. For example, for a square lithium battery cell with a height of 100 mm, the effective depth of the independent heat exchange groove is 92 mm, covering 92% of the cell height. This design specification has been optimized through thermal simulation, enabling simultaneous coverage of the current collector area at the bottom of the square lithium battery and the densely heated area on the side of the core.

[0029] Furthermore, the deep-groove enclosed heat exchanger is a hollowed-out liquid-cooled structure with a complex built-in flat microchannel liquid-cooling network. The flat microchannel liquid-cooling network introduces coolant through an inlet manifold located on the first side of the deep-groove enclosed heat exchanger. The flat microchannels uniformly guide the coolant to the branch channels surrounding and at the bottom of each independent heat exchange deep groove. The coolant flows upwards from the bottom within the flat microchannels and then converges at the outlet manifold located on the second side of the deep-groove enclosed heat exchanger. This fully enclosed fluid layout ensures that all five sides of the square lithium battery, except for the top electrode end face, are within the direct heat exchange range of the liquid coolant. To eliminate air gap thermal resistance caused by mechanical tolerances during assembly, this embodiment uniformly fills the gap between the square lithium battery and the inner wall of the independent heat exchange deep groove with alumina-based silicone thermally conductive interface material, ensuring that the total thermal resistance from the cell to the deep-groove enclosed heat exchanger is less than 0.05℃ / W.

[0030] As another key engineering detail of this invention, the flat microchannel of the deep-groove enclosed heat exchanger adopts a non-uniform cross-section design. In the 1 / 3 region near the liquid inlet, the internal width of the flat microchannel is narrowed to 1.8 mm. The Bernoulli principle is used to increase the local flow velocity of the fluid and enhance the Reynolds number, thereby improving the convective heat transfer coefficient in the region with a small inlet temperature difference. In the middle section of the channel and the liquid outlet region, the channel width is restored to 2.5 mm, and staggered turbulence-inducing micropillars with a height of 0.5 mm are set on the wall of the flat microchannel. These micropillars can disrupt the development of the boundary layer and induce local turbulence in the fluid, thereby compensating for the decrease in temperature difference driving force caused by the increase in fluid temperature, and thus achieving high thermal uniformity among the entire battery module.

[0031] The liquid cooling circulation loop connects the deep-groove enclosed heat exchanger, liquid storage tank, variable frequency water pump and radiator assembly in sequence through high-pressure resistant rubber pipes, forming a closed fluid circulation path. The circulation medium is a 50% concentration industrial ethylene glycol aqueous solution, which has stable chemical and physical properties in the range of -35℃ to 105℃, taking into account both heat dissipation and low-temperature antifreeze performance. Among them, the variable frequency water pump is a DC brushless electronic water pump, the speed regulation interface supports PWM signal speed regulation, and the internal Hall sensor is used to provide real-time feedback on the speed status. It can receive the first PWM signal output by the main controller to realize stepless adjustment of the coolant flow rate. The liquid storage tank is located on the upstream suction side of the variable frequency water pump. It is equipped with a labyrinth baffle structure inside to efficiently capture tiny air bubbles in the circulation system, prevent water pump cavitation, buffer coolant pressure fluctuations, accommodate coolant thermal expansion, and ensure the operational stability of the circulation system. The radiator assembly includes a high-efficiency heat pipe radiator body, and a first cooling fan and a second cooling fan installed on the windward side of the radiator body. The radiator body is welded from 42 aluminum flat tubes and 0.1mm thick corrugated fins, and the heat pipes enhance the secondary heat exchange efficiency. The first cooling fan and the second cooling fan are both high static pressure fans with a diameter of 120mm. The maximum airflow of a single fan can reach 60CFM, and they can be started, stopped and speed adjusted in stages according to the control signal of the main controller.

[0032] The data acquisition unit, as the system's sensing module, consists of 12 high-precision NTC thermistor sensors. These 12 NTC thermistor sensors are fixed to preset monitoring points on the battery module unit using high thermal conductivity adhesive. Among them, 4 are deployed in the low-temperature area near the inlet manifold, 4 are deployed in the high-temperature risk area at the physical geometric center of the battery module, and 4 are deployed in the area near the outlet manifold, comprehensively covering the hot spots and average temperature representative areas of the battery module to ensure the accuracy and representativeness of temperature acquisition. The temperature signals from each NTC thermistor sensor are connected to the 12-bit multi-channel analog-to-digital converter (ADC) built into the main controller via shielded twisted-pair cables. The main controller first uses a preprocessing algorithm combining median filtering and arithmetic mean filtering to filter out high-frequency electromagnetic interference in the vehicle environment from the collected temperature signals. Then, it calculates the real-time average temperature of the battery module using a weighted average algorithm, and obtains the real-time maximum temperature of the battery module by comparing extreme values, providing input parameters for subsequent control logic.

[0033] The main controller uses a 32-bit microprocessor based on the ARM Cortex-M4 core, with an operating frequency of 168MHz. It has multiple ADC acquisition channels and PWM output channels, which can meet the real-time requirements of large-scale floating-point operations of the fuzzy PID algorithm. The main controller is electrically connected to the data acquisition unit, the variable frequency water pump, the first cooling fan, and the second cooling fan. It internally stores and runs a fuzzy PID control program, which is executed to achieve closed-loop adaptive control of the cooling system.

[0034] In this embodiment, the core logic of the fuzzy PID control program includes a deviation calculation module, a fuzzification interface, a fuzzy inference engine, a PID parameter correction module, and a PWM output generator. The specific execution process is as follows: S1. Set the target preset temperature for the battery module, calculate the temperature deviation between the target preset temperature and the real-time average temperature, and calculate the rate of change of the temperature deviation; the relevant calculation formulas are as follows: ; ; In the formula, For temperature deviation, This is the real-time average temperature. Set the target temperature. The rate of change of temperature deviation, At the current sampling time, For the previous sampling time, The sampling period; S2. Map the temperature deviation and the rate of change of the temperature deviation to a preset fuzzy set universe of discourse; wherein, the universe of discourse for the temperature deviation is set to [-3℃, +3℃], and the universe of discourse for the rate of change of the temperature deviation is set to [-1℃ / s, +1℃ / s]; at the same time, the temperature deviation and the rate of change of the temperature deviation are divided into 7 fuzzy levels, namely negative large NB, negative medium NM, negative small NS, zero ZO, positive small PS, positive medium PM, and positive large PB; In the selection of membership functions, for the small deviation range of temperature deviation within the range of [-0.5℃, 0.5℃], a highly sensitive triangular membership function is adopted to enhance the steady-state control accuracy of the system; for the large deviation range of temperature deviation within the range of [-3℃, -2℃] or [2℃, 3℃], a trapezoidal membership function with faster response speed is adopted to ensure the rapid response capability of the system. S3. Based on a preset fuzzy control rule table, perform logical reasoning on the input fuzzy quantities and output the correction amount of the PID parameters; the logical reasoning includes: When the temperature deviation is positive PB, the system is in the initial stage of temperature rise response. To quickly suppress the temperature rise, a large positive proportional coefficient correction is output. At the same time, reduce the correction amount of the integral coefficient. To prevent integral saturation and overshoot, the differential coefficient correction amount... Choose the smaller value to ensure system startup speed; When the temperature deviation is within a moderate range and the rate of change of deviation is in the same direction as the temperature deviation, it indicates that the cell temperature rise trend continues, maintaining a large positive proportional coefficient correction amount. At the same time, a correction factor for the differential coefficients is introduced. This produces an advanced predictive and suppressive effect, curbing the rate of temperature rise; When the temperature deviation gradually approaches zero and the rate of change of deviation shows an overshoot trend, rapidly increase the differential coefficient correction amount. At the same time, reduce the correction amount of the proportional coefficient. Increase the dynamic damping of the system to make the temperature converge smoothly to the target value and suppress temperature overshoot caused by thermal inertia; When both the temperature deviation and the rate of change of the deviation are near zero (ZO), the system enters the steady-state phase and outputs a large integral coefficient correction. By eliminating residual static error in the system through integral action, the steady-state temperature control accuracy of the system is ensured to be within ±0.5℃. S4. Add the correction values ​​of the PID parameters to the preset base PID parameters respectively. , , The above yields the optimal PID parameters under the current operating conditions. The calculation formula is as follows: ; ; ; In the formula, the basic PID parameters , , All were obtained through pre-tuning via system step response experiments; Based on the optimal PID parameters, the final control output is calculated using the discretized PID increment formula. The calculation formula is as follows: ; In the formula, To control the output at the current moment, To control the output amount in the previous moment. This represents the temperature difference between the two previous moments; S5. Linearly map the control output to two independent PWM drive signals. The specific control logic is as follows: The first PWM signal has its duty cycle given in real time by the control output of the fuzzy PID algorithm, which directly acts on the speed control interface of the variable frequency water pump. By adjusting the duty cycle, stepless control of the coolant flow rate is achieved. When the cell heat load is lower than the heat load threshold, the water pump operates in the range of 20% to 30% of the rated speed to maintain low power consumption. When a rapid temperature rise caused by high-rate discharge is detected, the water pump operation is increased to 80% to 100%, and the water pump runs at full speed to achieve instantaneous high-power heat dissipation. The second PWM signal is used to control the fan speed of the heat sink assembly. The main controller executes a graded control strategy based on the real-time maximum temperature: when the real-time maximum temperature exceeds the first preset threshold, the first cooling fan is turned on and stepless speed regulation is performed through the PWM signal; when the real-time maximum temperature exceeds the second preset threshold, the second cooling fan is started simultaneously and runs at full speed until the maximum temperature of the battery module is lower than the safety threshold, so as to achieve dynamic matching between heat dissipation intensity and heat load.

[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control, characterized in that, The system includes a battery module unit, a liquid cooling circulation loop, a data acquisition unit, and a main controller; The battery module unit integrates several square lithium battery cells and a deep-groove enclosed heat exchanger. The liquid cooling circulation loop connects the deep-groove enclosed heat exchanger, liquid storage tank, variable frequency water pump and radiator assembly through pipelines to form a closed fluid circulation path for realizing external energy transfer. The data acquisition unit is distributed at multiple preset positions in the battery module unit and is used to acquire temperature signals that reflect the thermal state of the square lithium battery in real time. The main controller performs logical reasoning on the temperature signal collected by the data acquisition unit by executing a fuzzy PID control program, and generates a pulse width modulation (PWM) signal to adjust the coolant flow rate of the variable frequency water pump and the heat exchange intensity of the radiator assembly. The deep-groove enclosed heat exchanger adopts an integrated molding structure with a matrix arrangement of deep heat exchange grooves inside for placing square lithium batteries. The deep-groove enclosed heat exchanger also has a hollowed-out liquid cooling structure. The hollowed-out liquid cooling structure includes cooling liquid channels extending along the four side walls and bottom of the deep heat exchange grooves, which are used to form a fully enclosed heat exchange interface on the outer periphery and bottom of the square lithium batteries.

2. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 1, characterized in that, The deep-groove enclosed heat exchanger includes: The deep-groove enclosed heat exchanger is manufactured by controlled atmosphere brazing process and includes 60 independent heat exchange deep grooves. The inner wall dimensions of each independent heat exchange deep groove are precisely tolerant to the outer dimensions of the square lithium battery. The deep-groove enclosed heat exchanger is a hollowed-out liquid-cooled structure with a built-in flat microchannel liquid-cooling network. The flat microchannel liquid-cooling network introduces coolant through an inlet manifold located on the first side of the deep-groove enclosed heat exchanger. The flat microchannels evenly guide the coolant to the branch channels surrounding and at the bottom of each independent heat exchange deep groove. The coolant flows upward from the bottom in the flat microchannels and collects at the outlet manifold located on the second side of the deep-groove enclosed heat exchanger. An alumina-based silicone thermal interface material is uniformly filled in the gap between the square lithium battery and the inner wall of the independent heat exchange deep groove.

3. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 2, characterized in that, The deep-groove enclosed heat exchanger also includes: The flat microchannel of the deep-groove enclosed heat exchanger adopts a non-uniform cross-section design. In the 1 / 3 region near the liquid inlet, the internal width of the flat microchannel narrows to increase the local flow velocity of the fluid using Bernoulli's principle, thereby enhancing the Reynolds number and improving the convective heat transfer coefficient in the region with a small inlet temperature difference. In the middle section of the channel and the liquid outlet region, the channel width returns to 2.5 mm, and staggered turbulent micro-pillars with a height of 0.5 mm are set on the wall of the flat microchannel to induce local turbulence in the fluid.

4. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 2, characterized in that, The liquid cooling circulation loop includes: The liquid cooling circulation loop connects the deep-groove enclosed heat exchanger, liquid storage tank, variable frequency water pump and radiator assembly in sequence through high-pressure resistant rubber pipes, forming a closed fluid circulation path; The variable frequency water pump is a DC brushless electronic water pump with a speed control interface that supports PWM signal speed control. It has an integrated Hall sensor for real-time feedback of the speed status and receives the first PWM signal output by the main controller to achieve stepless adjustment of the coolant flow rate. The liquid storage tank is located on the upstream suction side of the variable frequency water pump. It is equipped with a labyrinth baffle structure inside to efficiently capture tiny air bubbles in the circulation system, prevent water pump cavitation, and buffer the pressure fluctuation of the coolant and accommodate the thermal expansion volume of the coolant. The radiator assembly includes a radiator body, a first cooling fan, and a second cooling fan; wherein, the radiator body enhances the secondary heat exchange efficiency through heat pipes; the first cooling fan and the second cooling fan are started, stopped, and speed adjusted in stages according to the control signal of the main controller.

5. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 4, characterized in that, The data acquisition unit includes: The data acquisition unit includes 12 NTC thermistor sensors; the NTC thermistor sensors are fixed to the preset monitoring points of the battery module unit by thermally conductive adhesive; among them, 4 are deployed near the liquid inlet manifold area, 4 are deployed in the physical geometric center area of ​​the battery module, and 4 are deployed near the liquid outlet manifold area, to cover the hot spot area and the average temperature representative area of ​​the battery module. The temperature signals from each NTC thermistor sensor are connected to the 12-bit multi-channel analog-to-digital converter module built into the main controller via shielded twisted-pair cables. The main controller first uses a preprocessing algorithm that combines median filtering and arithmetic mean filtering to filter out electromagnetic interference in the vehicle environment. Then, it calculates the real-time average temperature of the battery module using a weighted average algorithm, and obtains the real-time maximum temperature of the battery module by comparing extreme values.

6. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 5, characterized in that, The fuzzy PID control program includes: S1. Set the target preset temperature of the battery module, calculate the temperature deviation between the target preset temperature and the real-time average temperature in real time, and calculate the rate of change of the temperature deviation. S2. Map the temperature deviation and the rate of change of temperature deviation to a preset fuzzy set universe of discourse, wherein the universe of discourse for temperature deviation is set to [-3℃, +3℃], and the universe of discourse for the rate of change of temperature deviation is set to [-1℃ / s, +1℃ / s]; and divide the temperature deviation and the rate of change of temperature deviation into 7 fuzzy levels. S3. Based on the preset fuzzy control rule table, perform logical reasoning on the input fuzzy quantity and output the correction amount of the PID parameter; S4. Add the correction values ​​of the PID parameters to the preset base PID parameters respectively. , , The optimal PID parameters under the current operating conditions are obtained from the above. S5. Linearly map the control output to two independent PWM drive signals.

7. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 6, characterized in that, S2 further includes: in the selection of membership functions, for the deviation range of temperature deviation within the range of [-0.5℃, 0.5℃], a triangular membership function is used to enhance the steady-state control accuracy of the system; for the deviation range of temperature deviation within the range of [-3℃, -2℃] or [2℃, 3℃], a trapezoidal membership function is used to ensure the rapid response capability of the system.

8. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 6, characterized in that, The logical reasoning includes: When the temperature deviation is positive (PB), increase the positive proportional coefficient correction amount. At the same time, reduce the correction amount of the integral coefficient. ; When the temperature deviation is within a moderate range and the rate of change of the deviation is in the same direction as the temperature deviation, maintain the positive proportionality correction factor. At the same time, a correction amount for the differential coefficients is introduced. ; When the temperature deviation gradually approaches zero and the rate of change of deviation shows an overshoot trend, increase the differential coefficient correction amount. At the same time, reduce the correction amount of the proportional coefficient. Increase the dynamic damping of the system to allow the temperature to converge smoothly to the target value; When both the temperature deviation and the rate of change of deviation are at zero (ZO), increase the integral coefficient correction amount. The residual steady error is eliminated through integral action.

9. The deep-groove enclosed lithium battery liquid cooling system based on fuzzy PID control according to claim 6, characterized in that, The two independent PWM drive signals include: The first PWM signal has its duty cycle given in real time by the control output of the fuzzy PID algorithm, directly acting on the speed control interface of the variable frequency water pump. By adjusting the duty cycle, stepless control of the coolant flow rate is achieved. When the cell heat load is lower than the heat load threshold, the water pump operates in the range of 20% to 30% of the rated speed. When a rapid temperature rise caused by high-rate discharge is detected, the water pump operation is increased to 80% to 100%. The second PWM signal is used to control the fan speed of the heat sink assembly. The main controller executes a graded control strategy based on the real-time maximum temperature: when the real-time maximum temperature exceeds the first preset threshold, the first cooling fan is turned on and stepless speed regulation is performed through the PWM signal; when the real-time maximum temperature exceeds the second preset threshold, the second cooling fan is started simultaneously until the maximum temperature of the battery module is lower than the safety threshold, so as to achieve dynamic matching between heat dissipation intensity and heat load.

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