Research And Design Of Practical Contactless Charging System For Electric Vehicles

Inductively coupled contactless power transmission(ICPT),which is a technical change to the traditional wired power transmission,has established a relatively complete and mature theoretical system after nearly three decades of research and development.Currently,this technology has been applied in transportation,bio-medical,industrial automation,aerospace,consumer electronics and other fields,and there have been new products come out.The technology’s use in the field of wireless charging of electric vehicles is one of the hot research areas.However,there are many problems to be solved.This article’s research aims at the use of ICPT technology in electric vehicles’ charging systems,and strives to advance the technology to practical use.The contents and results of this thesis are summarized as follows:Firstly,this paper analyzes the structure of primary and secondary coils,which are used for energy transmission.The coils are regarded as a loosely coupled transformer and the equivalent electrical model based on mutual inductance model is established.This paper also uses capacities to compensate the leakage inductance.The advantages and disadvantages of four compensation networks are compared and,finally,the PSSP structure is chosen to be the compensation network of ICPT system.Secondly,the operation modes and commutation process of full-bridge inverter in ICPT system are analyzed and a ZVS soft switching condition is achieved.Additionally,based on the generalized modulation control method,current delay phase expressions in three common full-bridge inverter control modes are derived.At last,contrastive analysis of phase margin simulation is given.Thirdly,the stability of ICPT system is analyzed and,as a result,the boundary condition of system stability is derived based on the equivalent load.And for the load mutation problem,a negative feedback regulation mechanism based on the current phase tracking is put forward.Also,detailed analysis to the workflow control of this idea is given.Fourthly,based on the theoretical analysis,the design specification of ICPT charging system is defined.The designation flow of hardware circuit and the framework of control algorithm are illustrated.During the process of ICPT system design,various measures are taken to enhance the reliability and usefulness of the system,including soft start and soft-shutdown protection,inrush current suppression,filter capacitor discharge channel,overvoltage,overcurrent and thermal protection,noload protection,power-on sequence control and so on.Human interface is designed and a variety of communication protocols(including CAN communication,ZIGBEE communication and SCI communication)are used in the system to achieve feedback control between the primary and secondary side and the communication between various control modules.Fifthly,a complete test platform of ICPT charging system is built.The maximum output power is 2989 watts,whose maximum transfer efficiency can reach 83 percent.This platform can work in a coil spacing between 150 mm and 230 mm.Experimental results show the correctness and feasibility of system solutions,hardware and software design.Finally,the contents of this paper is summarized,and shortcomings and improvements of the designed ICPT system is proposed,while further research work being put forward.