Research On Maximum Efficiency Tracking Strategy Of Magnetically Coupled Resonant Wireless Power Transfer System

Compared with other types of wireless power transfer systems,magnetically coupled resonant wireless power transfer systems have broad application prospects in new energy,implanted medical and other fields due to their advantages such as longer transmission distance and high transmission efficiency.However,due to the influence of transmission distance,load,ambient temperature and so on,the actual system of this type will have load impedance matching problems and system frequency detuning phenomenon,and its transmission efficiency is obviously lower than the ideal value.In order to improve the wireless power transmission efficiency of the system,this paper establishes the steady-state efficiency models of four basic circuit topologies,and simulates and analyzes the influence of coil spacing,load impedance,and resonant frequency on the system transmission efficiency.The magnetically coupled resonant wireless power transfer system of the company is used as the research object,and the following work is mainly carried out:(1)Aiming at the load impedance matching problem of magnetically coupled resonant wireless power transmission system,an improved perturbation and observation method is proposed to achieve system impedance matching.First,through the analysis and comparison of six DC-DC topologies,the Buck-Boost circuit is selected as the impedance matching topology,and then the perturbation observation method is used to adopt different duty cycles in impedance matching to quickly track the optimal load of the system and reduce efficiency fluctuations.Finally,the effectiveness of the improved method is verified by the comparison results of the system simulation model in the resonance state.(2)Aiming at the frequency detuning problem of the magnetically coupled resonant wireless power transmission system,two frequency tracking control algorithms are proposed,and a maximum efficiency tracking control scheme is designed in combination with impedance matching.In view of the fact that the system is a nonlinear complex system with switching devices,from the control point of view,the real-time phase difference between the transmitter current and voltage is used as the input of the controller,and the output of the controller is used to regulate the frequency of the AC power supply at the transmitter.A model-free adaptive frequency tracking control method and an adaptive active disturbance rejection frequency tracking control method are presented,which do not rely on mathematical models for controller design.The research work not only gave the control principle structure diagram of the two methods,designed the corresponding mathematical expression of the controller,analyzed the system stability of the controller,but also built a system simulation model combining impedance matching and frequency tracking control to carry out simulation research.The simulation comparison results verify that the proposed two control methods,compared with the traditional PI control method,not only can maintain the resonant working state of the system transmitter in the case of a longer wireless transmission distance,but also have better resonant frequency tracking performance.However,combining impedance matching has obvious advantages in maintaining high system wireless power transmission efficiency.(3)The experimental prototype is designed and built with STM32F334 as the main control chip,and the application experiment verification of the model-free adaptive frequency tracking control method is carried out.The results further verify the effectiveness and engineering feasibility of the proposed control method.