Research On Maximum Power Point Tracking Control Of Exhaust Thermoelectric Generator Based On Thermoelectric Equivalent Circuit Model

Only about 25%of the energy released by the vehicle fuel combustion is used to drive vehicles and power onboard electrical appliances.It is an effective way to reduce the fuel consumption and CO₂ emission and improve the energy utilization efficiency to recycle the waste heat energy of vehicle exhaust.The semiconductor thermoelectric material with the significant Seebeck effect can convert thermal energy into electrical energy.The thermoelectric generator with thermoelectric material as the core component uses this physical property,taking the exhaust pipe wall of the engine as the hot end and air or engine coolant as the cold end,converts the temperature difference at both ends into electric energy and outputs it to the outside world.Compared with other exhaust gas waste heat recovery,thermoelectric generator has the advantages of no moving parts,no wear,no noise,long service life and so on.After the automobile exhaust gas passes through the thermoelectric generator,the heat energy is converted into irregular electrical energy,and the DC-DC converter at the subsequent stage converts this electrical energy into a stable voltage source and is connected to the vehicle power supply system.In this paper,the thermoelectric equivalent theory commonly used in the study of thermoelectric energy transfer mechanism is introduced into the study of recovery control to explore the relationship between the energy transfer mechanism and recovery control of the thermoelectric generator under the change of vehicle multi working conditions,and a new hybrid control algorithm is proposed to improve the recovery performance of the thermoelectric generator under the change of vehicle multi working conditions.And the main research contents are as follows:Firstly,the mechanism of thermoelectric energy transfer is analyzed by using the knowledge of thermodynamics.Based on Multisim software,the SPICE equivalent circuit model of single PN section of thermoelectric module is established.On this basis,the equivalent circuit model of single thermoelectric chip is further established.The steady and dynamic characteristics of the TEG system are simulated and analyzed.The SPICE simulation results are compared with the ANSYS simulation results,and the output characteristics of the thermoelectric coupling system are obtained.A small thermoelectric device is set up to test,which verifies the correctness of the theoretical analysis.Secondly,according to the principle of MPPT tracking,the MPPT tracking model is established.The control algorithm of MPPT is studied,and a new hybrid control algorithm is designed based on constant voltage method and hysteresis comparison method.According to the coupled output characteristics of the thermoelectric equivalent circuit model,the key parameters of the algorithm are optimized.Finally,based on the internal logic of the algorithm model,the new hybrid MPPT tracking algorithm is compared with other traditional algorithms.Then,this paper considers the modeling environment of the algorithm model,builds a complete thermoelectric generator system model based on MATLAB/Simulink,including the thermoelectric material nonlinear power characteristics thermoelectric generator output power model and the system recovery circuit based on MPPT control,and then establishes four simulation model of the MPPT method,considering the actual working conditions when the TEG is applied to the vehicle,simulates the constant working conditions when the vehicle maintains a constant speed and the sudden working conditions when the vehicle decelerates rapidly,and the newly proposed hybrid maximum power point tracking algorithm Compared with other traditional algorithms,the simulation of the optimization of the hybrid algorithm is finally compared.Finally,the maximum power point tracking controller of the thermoelectric generator system based on the Buck-Boost circuit is designed,and the control program is written based on the MCU control chip STM32F103.The controller integrates the maximum power tracking control and the electric energy matching output system,so that the thermoelectric generator system can match the vehicle power supply.The voltage can be maximized by adjusting the recovery circuit load.The recovery control test platform of the thermoelectric power generation system was built to realize the maximum power point tracking control of the system energy recovery.