Research On Temperature Control Characteristics Of Liquid Cooling Plate

With the continuous development of power electronics technology,electronic devices have shown a trend of integration,miniaturization and intelligence,and energy density has also increased.The thermal design of electronic equipment is to ensure the components are always in the operating temperature range,also to ensure the normal operation and stability of the electronic equipment or the entire system.In space thermal control,external complex thermal load and internal component power changes simultaneously,so traditional passive cooling method for single working conditions become more and more difficult to satisfy the emerging needs,so the active temperature control system plays an increasingly important role.The liquid-cooled plate has a relatively simple and reliable structure,mature theoretical support and more potential heat dissipation than air-cooled heat.Research on liquid-cooled plates focuses on strengthening heat transfer or structure optimization,but lacks research on active temperature control of liquid-cooled plates.The establishment of the temperature control system includes mathematical modeling of the controlled object and controller design based on the mathematical model.In fact,due to the influence of noise and other factors in the actual operation of the equipment,the model identification is difficult,and the accuracy of the mathematical model largely determines the reliability of the controller.Therefore,it is necessary to carry out the model identification research of the liquid-cooling plate,improving the accuracy of the mathematical model to describe the actual process,and design a reliable and simple controller parameter tuning method to improve the design efficiency of the control system.Fractional calculus is more suitable for describing physical processes with memory and inertia.In the field of control,fractional order transfer function and fractional order control strategies are proposed.Compared with the traditional first-order and second-order transfer function,the fractional order transfer function is more accurate in describing the physical process due to its order flexibility.Fractional-order controllers also provide more flexible controller parameter design choices.The main research of this paper mainly include the following parts:(1)In this paper,an active liquid-cooling plate temperature control experimental platform is designed and built.Modbus communication protocol combined with RS-485 bus technology to realize real-time two-way communication of data acquisition and feedback control of the experimental platform.The lumped parameter method was used to simulate the heat transfer process in the serpentine channel liquid-cooling plate.Taking the temperature step response of the heating element as the simulation object,the results shows that the liquid cooling plate satisfies the heat exchange requirement of the electronic component and can meet the heat exchange requirement of40W/cm~2.The numerical simulation results of the lumped parameter method generally reflect the temperature dynamic process of the simulated heating element under the heat dissipation condition of the liquid cooling plate under the action of external heat flow,which provides data support for the realization of the thermal control process.(2)Aiming at the problem that the identification method based on time domain analysis can not find the critical point accurately under the influence of noise,an identification method combined with frequency domain analysis is proposed.Firstly,the dimensionless time is introduced to simplify the closed-loop expression of the system and obtain the relation of time constants in the second-order transfer function.Secondly,for second-order with and without time-delay transfer function,according to the phase-frequency characteristic curve analysis and Nyquist criterion,combined with the critical oscillation frequency of the system,another relational expression of the transfer function time constant is obtained.The experimental and theoretical results show that the identification method combined with frequency domain analysis is better than the traditional method under the influence of noise.The absolute error index is 11.25,while the absolute error index based on the time domain data is 17.49.Based on the the second-order transfer function,the PID controller was designed by SIMC-PID parameter tuning method.The control results were obtained in both experiments and simulations,and the control process was stable and accurate.(3)This paper theoretically verifies the superiority and flexibility of fractional order systems and fractional order controllers.A new transfer function form combining integer order and fractional order is proposed.The particle swarm optimization algorithm is used to identify the step response of the heating element temperature.The experimental results show that the accuracy of the fractional transfer function is significantly better than the traditional second-order transfer function,the absolute error index is 6.848,while the second-order transfer function is 11.25.According to the stability criterion of controller design,the corresponding PI~?D~?controller is designed.The fractional-order controller shows a better control performance during the experiment.The control process was completed in 20s,while the integer-order controller completed the same temperature step index for 60s,and the actuator control was more stable without large oscillation occurs,which is beneficial to the long-term stable operation of the actuator.This paper provides relevant thermal data for water-cooled plate temperature control,and provides important technical support for water-cooled plate test platform design,model identification,and controller design.