Abstract: The emergence of wireless power transmission（WPT）technology overcomes the strict requirements

of traditional wire transmission process on transmission site conditions，maintenance convenience and security，

which has a wide range of application scenarios. In the WPT technology，the misalignment tolerance characteristics

between the primary and secondary coils directly affect the quality，efficiency and reliability of the power

transmission. The loosely-coupled transformer was optimized and the corresponding compensation network was

designed to enhance the misalignment tolerance characteristics and output stability. The D.D.D. loosely-coupled

transformer designed has strong misalignment tolerance ability and good magnetic shielding characteristics.

Considering the influence of magnetic flux leakage，a symmetric PS/SP topology was proposed based on the

traditional transformer equivalent model. Through frequency modulation control，the input impedance angle of the

system was maintained to zero，and the high-efficiency and stable output of the system was realized. Finally，in order to verify the theoretical analysis，a 250 W experimental platform based on the D.D.D. loosely-coupled transformer was built，and the system efficiency reached 88%.

      Key words: wireless power transmission（WPT）；loosely-coupled transformer；misalignment tolerance；PS/SP

compensation topology