Research On Dynamic Performance Optimization Method Of Buck-WPT System Based On Controllable Inductor

With the rapid development of modern industry,people are paying more and more attention to the problem of air pollution.In the society,there is a growing call for reducing the exhaust emissions of fuel-powered vehicles.Electric vehicles have gradually entered people’s lives because of their advantages of zero emissions,environmental protection and energy saving.Wireless power transfer(Wireless Power Transfer,WPT)technology makes electric vehicles have a more convenient,safe and fast charging method,and makes the charging method of electric vehicles more intelligent and automated.Therefore,wireless charging technology is becoming more and more important for the development of electric vehicles.This article takes Buck-WPT system as the research object.The Buck-WPT system refers to a wireless charging system in which a Buck circuit is added to the pre-stage circuit of the WPT system for power adjustment,and is one of the commonly used topology structures of the wireless charging system.Because of its high order and non-linear characteristics,the control of the system is relatively difficult.And because the system often works under multiple load conditions,its loading performance is threatened.This paper aims at the problems of current and voltage overshoot during system startup and load switching,longer start-up time,and excessive primary side resonance current in the no-load Buck-WPT system of SS-type resonant network.A control technology based on controllable inductance is proposed to optimize the dynamic process and load performance of the system.The main research and design work of this article are as follows:Firstly,according to the working principle of the controllable inductor,the magnetization process of the controllable inductor and its equivalent circuit are introduced,and its working point is analyzed according to the equivalent circuit.The feasibility of the scheme is verified by the simulation of the finite element software Comsol and the inductance parameter design selection method is proposed.Secondly,taking the Buck converter as the research object,the method of parameter selection is discussed first,and the system trajectory equation is preliminary analyzed.The method of using controllable inductor to optimize the turn-on trajectory is discussed,and the Buck converter enters a steady state without overshoot by dynamically adjusting the inductance value.Aiming at the problem of load switching,a PI algorithm is proposed to control the inductance of the controllable inductor,which speeds up the dynamic response of the system and reduces the jitter of the output voltage of the system.Simulation also verifies the correctness of the scheme.Then,based on the Buck converter,the WPT system is used as its special load,the state-space equation of the Buck-WPT system is derived,and the dimensionality reduction description method of the phase trajectory in its three-dimensional space is studied.By analyzing the operation trajectory of the phase trajectory during the start-up phase,it is proposed to use a controlled inductor to control the trajectory during the start-up phase of the system,so that the system can quickly enter a steady state without overshoot during a turn-on.For the problem of load switching,the PI algorithm is used to control the Buck converter.The output current is constant,which ensures that the output voltage of the secondary side remains unchanged,improves the stability of the system,and simulates and verifies the correctness of the scheme.Then,for the no-load large current problem in the Buck-WPT system of the SS resonant network,it is proposed to control the inductance in series with the primary resonant network,and dynamically adjust the inductance of the controllable inductor to adjust the primary impedance,so that maintaining the primary resonance current below the safe value under no-load improves the on-load performance of the system,and simulation verifies the correctness of the scheme.Finally,in order to verify the feasibility and effectiveness of the dynamic process and on-load performance optimization scheme in this paper,Matlab software was used for simulation,and the simulation results were compared and analyzed.