Research On Multiple Parameters Estimation Algorithm Based On Transmitter Side In Wireless Power Transfer System

With the continuous development of wireless power transfer technology and its commercialization process,its security issues attract more and more attention.Foreign metal object detection(FOD)has become a necessary function in practical application of wireless power transfer.Furthermore,due to the electrical isolation nature of wireless power transfer system,how to obtain the information on load side has become one of the key issues.In order to solve this problem,this paper combines the FOD method based on parameter detection with the system parameter estimation,and proposes a multiple parameters estimation algorithm based on transmitter side information.The algorithm realizes the FOD function while estimating the key parameters to assist system to achieve control target.The main work of this paper are as follows:At first the architecture and principle of wireless power transfer system are introduced,and the characteristics of the system are analyzed by establishing an equivalent circuit model.In addition,the characteristics and application scenarios of different inverter topologies are compared and analyzed,and the corresponding soft switching conditions are given,providing a theoretical foundation for the subsequent research.Secondly,combined electromagnetic theory and finite element simulation,the influence of common foreign metal object on the inductance,internal resistance and mutual inductance of coils at different frequencies,positions and distances is analyzed,providing theoretical foundation for the proposed FOD method.The validity of soft-switching condition of the ClassE inverter and the changing rules of system operating conditions are studied.In addition,an experimental prototype is built up to verify the theoretical analysis.Then a multiple parameters estimation algorithm based on transmitter side information is proposed,which can simultaneously estimate the mutual inductance,the load resistance and the receiving coil inductance or the receiving side resonance capacitance.The algorithm combines frequency sweeping and gradient descent approach to make the accuracy of the estimation results insensitive to measurement errors and noise.The algorithm adopts feature scaling to accelerate the convergence speed,and the objective function is also strictly proved as a convex function to ensure the uniqueness of the solution.Furthermore,an experimental prototype is set up to verify the accuracy of estimation results and the FOD function.Finally,the entire process including sampling and algorithm calculation is implemented on a single circuit board of STM32H7 processor.In addition,the algorithm's solving approach is optimized into a matrix form,which facilitates the deployment and implementation of the algorithm on the processor.The procedure flow of the algorithm on the processor is also introduced in details.The experimental results show that the estimation results are accurate and the solving speed of the algorithm is fast.At the same time,the foreign metal object around the coil can be effectively identified.The experimental prototype system verifies the effectiveness and practicability of the algorithm.