Energy Management Control Strategy Of Mild Hybrid Powertrain

With the year-on-year growth of car ownership,the energy shortage and environmental pollution problems caused by traditional vehicles have become increasingly severe.Faced with the fuel consumption regulations for vehicles and the limitations of pure electric vehicles,hybrid electric vehicles came into being,which also have the advantages of traditional vehicles and pure electric vehicles.The mild hybrid electric vehicle(MHEV)gets a lot of attention because of its little modification to the original powertrain of the vehicle,low cost,short production cycle and easy to mass production.This paper takes a traditional vehicle with a turbocharged engine as the research object and develops a mild hybrid powertrain for it.It conducts a research which aims at the energy management control strategy and the strategy optimization considering turbocharged engine response.It builds a vehicle simulation and bench test platform to verify the designed control strategy.The specific research contents are as follows:Firstly,it designs the configuration of the mild hybrid powertrain for the target vehicle and makes the selection and parameter matching for the key components of the powertrain.It includes selecting the type of integrated motor for starting/generating and determining the peak torque,peak power,maximum working speed and other motor parameters.It also includes selecting the power battery type and determining the power battery pack parameters such as the rated voltage of the power battery pack,capacity and number of single batteries in series and parallel connection.Second,it uses GT-SUITE software and Matlab/Simulink software to jointly build a forward simulation and analysis platform for the mild hybrid powertrain.It builds models such as engine,motor,power battery pack,drive train,driver and vehicle longitudinal dynamics,which lays the foundation for subsequent simulation studies.Third,it selects the instantaneous optimization method which is based on equivalent consumption minimization strategy(ECMS)to formulate an energy management control strategy.In the process of formulating the control strategy,it respectively establishes the future supplementary model of electric energy and the future consumption model of electric energy based on the different power flow directions.It determines the equivalent fuel consumption rate of the powertrain as the objective function through defining equivalent factor,state of charge(SOC)compensation for the power battery pack,regenerative braking correction and corresponding derivation.It carries out optimization calculation based on the constraints and obtains the energy distribution relationship between the engine and the motor.It compiles the control strategy into the vehicle model and carries out the comparative simulation analysis with the original traditional vehicle model and the MHEV model without the control strategy(only automatic idling start-stop and regenerative braking function).The simulation results prove that the control strategy is effective in saving oil.Finally,it considers the impact of turbocharged engine response on dynamic performance and fuel economy of the vehicle and carries out the motor power compensation strategy design which is based on the original energy management control strategy.In the process of formulating the compensation strategy,it sets the allowable compensation coefficient and SOC compensation coefficient for the motor to determine the motor power compensation amount based on the difference between the total demand output power and the total actual output power of the engine and the motor,the motor power compensation limit and SOC of the power battery pack.Under different allowable compensable coefficients of the motor,it conducts the simulation analysis of the vehicle's dynamic performance.The simulation results show that the compensation strategy can effectively improve the vehicle's power and the power improvement effect of different allowable compensation coefficients of the motor is different.The fuel economy of the vehicle is verified and analyzed by setting up a performance test bench of the mild hybrid powertrain.The test results show that the compensation strategy can reduce the fuel consumption of the vehicle and the fuel saving effect of different allowable compensation coefficients of the motor is different.This study has some reference application value for the development and optimization of energy management control strategy for the mild hybrid powertrain,and it has a positive impact on the promotion of mild hybrid electric vehicles.