Research On Energy Management Strategy For Plug In Hybrid Electric Bus Considering Motor Temperature Rise Effect

In the current situation of energy shortage and increasingly severe environmental pollution,hybrid electric vehicle(HEV),as a representative technology of new energy vehicles,has been widely used in the field of urban transportation due to its excellent performance in energy saving and emission reduction.The energy management strategy(EMS)is designed to achieve superior fuel economy and dynamic performance for HEVs by coordinating multiple energy sources.As one of the main power system components of HEV,the motor needs to start frequently or work for a long time.In addition,the motor may encounter thermal problems under harsh operating conditions,leading to the failure of key components.Moreover,the output power is usually limited by the thermal limit capacity of the motor,such as the winding temperature rise limit under low speed and high torque.In this case,the motor may not meet the optimal power allocation requirements of the EMS,which seriously affects the dynamic performance and fuel economy of the vehicle.Therefore,designing an EMS for HEVs with the consideration of the temperature rise effect of the motor is particularly important.In this dissertation,the plug-in hybrid electric bus(PHEB)is taken as the research object,and the equivalent consumption minimization strategy(ECMS)is used under the model predictive control(MPC)framework to solve the rolling optimization problem.The battery power consumption is equivalent to fuel consumption,and the motor temperature is taken as the optimization item of the cost function to construct the EMS objective function,so as to realize the fuel economy of the vehicle and avoid the motor overheating.The research content of this dissertation is as follows:First,the powertrain component of the PHEB is modeled.Based on MATLAB/Simulink platform,the main vehicle component models such as engine,motor power,power battery and transmission system are built by combining the vehicle dynamics principle and the experimental data of the power components.The thermal characteristics of the motor are studied on the basis of traditional dynamic system modeling.In order to make the thermal model predict the temperature rise of the motor quickly and accurately,the iterative method is proposed to obtain the real harmonic current with high accuracy,and the motor thermal model is established by associating it with the thermal overload curve.Moreover,this part lays the foundation for the subsequent EMS research based on the motor temperature rise effect.Then,the EMS research of plug-in hybrid power system is carried out.Considering the nonlinear and multiple constraints of the vehicle power system,in order to achieve good fuel economy and avoid excessive motor temperature affecting EMS,a model predictive control strategy with equivalent consumption minimization(ECMS-MPC)based on motor temperature rise effect is proposed.By combining the ECMS algorithm with the MPC framework,the EMS equates the battery power consumption to the fuel consumption,and takes the motor temperature as the optimization term of the cost function to construct the EMS objective function.Moreover,grey wolf algorithm is used to solve the relevant weight coefficients of the optimal objective function to achieve optimization.In addition,the effectiveness of the strategy is verified by simulation.Finally,the ECMS-MPC energy management strategy is tested by Hardware in the loop(HIL).The related hardware circuit is designed and HIL test platform is built.The EMS proposed in this paper is downloaded to the real controller,and the control effect of the EMS is verified in the real-time simulation environment.By comparing the test results with the simulation results,the HIL test verifies that the proposed EMS is effective and real-time.