Impedance Analysis and Design of IPT System to Improve System Efficiency and Reduce Output Voltage or Current Fluctuations

With the increase of load resistance, the impedance angle of the rectifier with passive
C
filter also increases, which may have some negative effects on the characteristics of the inductive power transfer (IPT) system. This article presents an impedance analysis method for
C
-filter rectifiers in continuous conduction mode. The calculation formula of critical load resistance is given and the relevant values are calculated. An improved
C
-filter rectifier circuit is proposed to reduce the phase angle of the IPT system. A very tiny capacitance is connected in parallel at the input end of the rectifier to reduce the impedance angle as load resistance changes, with hardly increased costs. This improved method not only improves the system efficiency, but also reduces the fluctuation of output voltage or current. Simulation and experiment results verify the feasibility of the proposed topology. A 1 kW prototype with primary series, secondary series compensation topology was built. The maximum system efficiency from dc power supply to the load is 94.5%. The efficiency under rated load is as high as 93%. Compared with traditional method, it has increased by 0.6%.