Research And Implementation Of Maximum Efficiency And Maximum Power Switching Strategy With Adaptive Coupling Coefficient

Magnetic Coupled Wireless Power Transfer(MC-WPT)technology is a kind of power transmission mode,which uses high frequency electromagnetic field as transmission medium and transmits energy from transmitter to receiver.It can effectively solve the power supply problem of equipment in special electric occasions,and it has the advantages of safety and flexibility.In these practical applications,when the load of the MC-WPT system changes and the relative position of the magnetic coupling mechanism changes,the system will deviate from the optimal operating point,resulting in a decline in the transmission performance of the system.At the present,the impedance matching method is mainly used to solve the problem of maximum efficiency or maximum power dynamic tracking when the load of the system changes,while the research on how to optimize the transmission performance when the relative position of the magnetic coupling mechanism changes is relatively less.However,there are relatively few studies on how to optimize the transmission performance of the system when the relative position of the magnetic coupling mechanism changes.Therefore,this paper takes the wireless charging system of UAV(Unmanned Aerial Vehicle)as the research object,aiming at finding out the control strategy for improving the transmission performance of MC-WPT system with variable coupling coefficient,taking into account the security and stability of the system.The following research work has been carried out:(1)Aiming at the characteristics of variable coupling coefficient,variable load and weak coupling of UAV wireless charging system and its main performance indicators,the advantages and disadvantages of common impedance matching methods are compared and analyzed.The schemes of increasing impedance matching method of DC-DC converter and LCC-S compensation topology are determined.(2)In order to solve the problem that the system output power cannot meet the power requirement under the condition of variable coupling coefficient and load,maximum efficiency and maximum power switching mode is proposed to improve the transmission performance of the system.Firstly,the AC impedance model of LCC-S MC-WPT system is built and analyzed to determine the load conditions and their influencing factors for achieving maximum efficiency and maximum power tracking mode.The impedance transformation range of DC/DC circuit is analyzed,and the dynamic identification method of coupling coefficient of the system is given to effectively correct the optimal load value of the system.(3)The design method of switching control strategy for maximum efficiency and maximum power tracking is given.On the premise of satisfying the output power level,the system first enters the maximum efficiency tracking mode.When the system coupling coefficient decreases and the output power is the required power,the system enters the constant power output mode.If the coupling coefficient of the system continues to decrease,the maximum power tracking mode will switch to the maximum power tracking mode when the output power is the same as the required power.(4)In MATLAB/Simulink,the maximum efficiency tracking mode,the maximum power tracking mode,the maximum efficiency and maximum power switching mode are simulated and analyzed,and the experimental device is built to verify.The simulation and experimental results prove the validity and correctness of the proposed maximum efficiency and maximum power switching mode control strategy.