Research On Control Strategy With Primary Current For Multi-transmitter Switched Wireless Power Transfer System

Compared with the traditional plug-in charging mode,wireless power transfer technology has many advantages,and it is also one of the future directions of energy transmission.Generally speaking,efficiency and power are two important indicators for evaluating the quality of wireless power transfer system.However,in actual working conditions,due to the uncertainty of the position of the receiving coil,the lateral misalignment between the receiving coil and the transmitter coil often occurs.As the misalignment distance between coils increases,mutual inductance and coupling coefficient will decrease,which will inevitably affect the efficiency and power of the WPT system.Therefore,it is of great significance to study the problem of misalignment between coils for improving the stability of WPT system.In this paper,the relationship between the efficiency of each working mode of the transmitter and the primary side current is deduced through theoretical analysis on the basis of the multi-transmitter switching coupling mechanism studied by the research group.Then,a switching control strategy based on the primary current is proposed to keep the system efficiency at a high level under misalignment.In addition,in order to solve the problem that coil misalignment will cause the output power fluctuation of the system at the same time,this paper analyzes the power control based on adjusting the input voltage,and deduces the relationship between the required regulating voltage and the primary current.Finally,the theoretical derivation of the power control strategy is verified by an experimental prototype.The primary study contents completed as follows:(1)On the basis of the multi-transmitter switching coupling mechanism,the switch group at the transmitter and the primary compensation circuit are optimized,and the working principle of the coupling mechanism and the coupling characteristics under lateral misalignment are analyzed.(2)A multi-transmit WPT switching control strategy based on the primary current is proposed to achieve accurate switching of the optimal working mode under misalignment.A two-step commutation method is designed to avoid the phenomena of excessive peak voltage or current cut-off at the primary side of the system at the moment of switching between two working modes.Finally,an experimental prototype is built to verify the correctness of the switching control strategy and the two-step commutation.The performance of the multi-launch switching coupling coil is analyzed and compared with that of the circular and square array coupling coil.(3)The output power fluctuation mechanism of multi-transmitter switching WPT system with coil misalignment is analyzed,and the power control based on adjusting input voltage is theoretically deduced.Finally,the theoretical derivation is verified by the system experimental prototype.