Research On Control Strategy And Key Component Of Fuel Cell Vehicle Powertrain

In order to solve the problems of climate warming and energy shortage,fuel cell vehicles came into being.However,there are still many problems to be solved: the design of key components,power system energy management,battery capacity decline and conversion efficiency.In this thesis,the power system modeling,main components design and energy management control strategy of fuel cell vehicles are studied.Firstly,the FCEV power system is analyzed,focusing on the fuel cell system,power battery,super capacitor and driving permanent magnet motor.Based on the dynamic performance of a fuel cell vehicle and the cooperation between multiple energy sources,the characteristic parameters of key components are matched,and the power system is modeled and simulated using MATLAB/Simulink.Based on the second order RC model of the battery,the performance of the extended Kalman filter(EKF)and the Unscented Kalman filter(UKF)for SOC estimation is compared,and the estimation accuracy of UKF is relatively high.The detailed design and research are carried out for the driving permanent magnet motor,and the motor test bench is designed.The efficiency characteristics,temperature characteristics and back EMF of the motor are tested to verify the performance of the designed motor.In order to achieve the coordinated control of the whole vehicle and key subsystems,with the goal of developing VCU,the control strategy of the power system application layer is deeply studied.First,the software architecture of the vehicle controller model is discussed,focusing on the fuel cell system start stop strategy,battery management system,motor control strategy and regenerative braking energy recovery strategy.For regenerative braking system,a braking force distribution strategy based on fuzzy control is designed.The results show that the system can fully and effectively maintain the battery SOC and super capacitor SOC,which verifies the rationality of the proposed fuzzy control system;The air supply system is responsible for supplying air that meets the pressure and flow conditions,which is essential to ensure the effective reaction of hydrogen.In this thesis,a dynamic model of the air supply system including the compressor and the supply pipeline is established.The transient characteristics of the air supply system are simulated through theoretical simulation.The simulation results show that the model can effectively predict the transient behavior of the compressor and fuel cell during operation.The air compressor driving 85 k W fuel cell is designed with emphasis.The rotor structure of high-speed motor and impeller is proposed,supported by air bearing,and the air compressor test bench is built to verify the pressure and flow characteristics of the air compressor.The noise characteristics,start stop characteristics and inclusive characteristics of the air compressor were tested,which further verified the on-board characteristics of the air compressor and promoted its industrial application.Energy management strategies and parameter optimization have an important impact on the performance of FCEV,and multiple objectives including fuel consumption,power performance and component degradation need to be considered.In this thesis,an auxiliary energy system composed of batteries and super capacitors is established.Combining the analysis ability of wavelet transform for transient signals and the control ability of fuzzy control for multi parameter and nonlinear systems,a multi energy source control algorithm based on wavelet-fuzzy control is studied.Particle Swarm Optimization(PSO)is used to establish a multi-objective optimization problem The fuel cell has the lowest power and the lowest cell degradation.The system characteristic parameters and control parameters are optimized simultaneously.Through the HIL platform based on dSPACE,the vehicle model and energy management strategy are verified.