Study On Optimization Design Method And Control Strategy For Electric Vehicle Dynamic Wireless Power Transfer System

With the continuous popularization of electric vehicles(EVs),the traditional contact-type charging mode(connector plugging and unplugging mode),which exists some serious drawbacks such as electric leakage,contact loss,mechanical wear and interface limitations.Besides,there remain some problems such as limited energy storage,the bulky and expensive on the board pack battery pack,which greatly restrict the development and promotion of electric vehicles.The Electric Vehicle Dynamic Wireless Power Transfer(EV-DWPT)system based on the wireless power transmission technology transmits the energy in a non-contact mode through the power supply rails buried under the road,thereby realizing the continuous power supply during the driving process of the vehicle,and ensuring the real-time dynamic power supply for EVs.The wireless supply method can overcome the problem of endurance limitation of the battery pack.On the other hand,the dynamic wireless supply method can reduce the capacity configuration of battery pack,or even the battery pack can be cancelled.This paper aims at the long-distance EV-DWPT system,focusing on the intensive study about the optimization design of the rail system,the switching reliability problem of the rail,the control strategy of dynamic operation for the rail system and the system robustness problems.The work of the thesis provides important support for the plan,design,implementation and operation of the dynamic wireless supply system for electric vehicles.The main research work of this paper is as follows:(1)Aiming at the problems of poor reliability and high construction cost of the system in the application of a long-distance EV-DWPT system,a new type of rail configuration and driving mode is proposed: rail group drive mode,and the structure and working mechanism of the mode are analyzed.Then,taking the system efficiency and construction cost as the objective function,the multi-objective planning model of rail group drive mode is established under the constraints of the electrical stress,the coupling coefficient,length of the high frequency power line and length of the power supply rail.Aiming at the established model,an improved adaptive genetic algorithm(IAGA)is proposed to solve the problem,and the improvement and flow of the algorithm are explained.Finally,an example is given to verify the feasibility of the proposed model and algorithm.(2)Aiming at the problem of rail operation state identification,a state identification method based on inverter voltage detection is put forward.By analyzing the variation trend and magnitude of the inverter voltage,various states in the system operation process are identified,which provides a basis for the discrimination of the rail switching time.There is no need to add an extra device to transmit the signal of the proposed method,which can directly reflect the primary side inverter voltage,avoid the interference and reduce the cost of the system.To the problems of large switch stress and inductance voltage spike in the hard switching mode of power supply rails,a soft switching method based on energy free oscillation is proposed,which realizes the safe switching of the rails.The proposed switching method does not require complicated control strategy,which is easy to implement.Besides,the electromagnetic transient model of the system is established,and the numerical expression of the relevant variables in the switching transient process is obtained.Finally,the simulation and experiment verify the effectiveness of the state identification method and the soft switching method.(3)Focusing on the problem of time-sharing supply of the rails in the existing EV-DWPT system,the rail group control strategy during the vehicle operation cycle is proposed,and the system operation cost is minimized under the guarantee of normal operation of the system.Firstly,the optimization variables are explained.Secondly,the driving characteristics of the vehicle and the energy variation characteristics of the energy storage device are analyzed.Then,the minimum system annual operating system cost is taken as the objective function,and a control model for rail group is established under the constraints of the device energy and the length of the supply rails.Finally,the particle swarm genetic algorithm(PSGA)is used to solve the problem.The optimal capacity of the energy storage device and the control scheme of the rail are obtained,and the sensitivity of the system parameters is analyzed.(4)Focusing on the load disturbance and randomness problems during the operation of the EV-DWPT system,the equivalent circuit model of multi-load operation is given firstly,and the constraints of avoiding multiple resonance points in the system design process are obtained.Secondly,the Generalized State Space Averaging(GSSA)model and the GSSA model considering parameter perturbation are established.Based on this,an H? controller based on the hybrid sensitivity is proposed to improve the system robustness for the stochastic dynamic process of the load.Besides,the nominal performance,robust stability and robust performance of the controller are analyzed.Finally,the feasibility of the designed H? robust controller is verified by the simulation and experiment.