| With the enhancement of people’s environmental awareness and the development of new energy industry,electric vehicles have become one of the new hotspots in the global automotive field.More and more countries and enterprises have begun to vigorously develop electric vehicles.At the same time,Wireless Power Transfer(WPT)is increasingly valued for its safety,reliability,and efficiency.The application of wireless power transfer to the electric vehicles has become a hot direction in the field of scientific research.The wireless charging technology of electric vehicles can be divided into two types: static wireless charging technology and dynamic wireless charging technology.Static wireless charging technology can solve the safety problem of wired charging piles,but it can’t do anything to solve the endurance problem of electric vehicles.Dynamic wireless charging technology can provide power to the moving cars through online power supply,greatly improving the electric vehicles travel distance.However,due to the high power demand,the dynamic wireless charging system keeps changing the mutual inductance value during driving,which results in a large fluctuation range of the system output of a single pick-up coil and an unstable output.In order to solve this problem,this paper designs a double pickup dynamic wireless charging system.Then,according to the output demand and input change of the system,a control strategy which can quickly respond to the system change and maintain the output stability is designed by using the fuzzy-PID compound algorithm.Firstly,according to the requirement of high power dynamic wireless charging system,the suitable secondary connection mode is selected.Then the constant current characteristic of LCC WPT system is analyzed.It can ensure that the output power of pickup mechanism is only affected by mutual inductance.Then analyzes the circuit characteristics of the pickup mechanism when DC link is parallel connected with Boost circuit,and defines the control objectives of the system.This paper then studies the mutual inductance change in the dynamic process of the coupling mechanism,as well as the charging characteristics of the battery load,and designs control strategies at different stages.In the constant current stage,the duty cycle is adjusted according to the mutual inductance of the two pickup coils and the transmitting coils to distribute the current.In the constant voltage stage,two voltage regulating circuits adopt the same duty cycle,and each branch automatically distributes the output current according to mutual inductance.In order to meet the fast demand of dynamic WPT system,the fuzzy-PID algorithm is selected to implement the control strategy.When the mutual inductance changes greatly,the deviation between the output current and the reference current is large.In order to make the system reach the working point quickly,the fuzzy controller is used to control it.When the error of the fuzzy controller is small,the PID controller is used to control the system in order to reach the steady-state working point.Finally,a 40 kW LCC double pickup wireless charging system simulation model is built in MATLAB/Simulink.Simulation of mutual inductance change at 20 km/h vehicle speed.By detecting the voltage and current of the load,the validity of the system control in the pre-charging stage,the constant current charging stage and the constant voltage charging stage is verified.Build a set of double-emission and double-pickup experimental device,move the pickup.and verify effectiveness of the control strategy by detecting the load voltage and current. |
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