Harmonic Modeling and Analysis of Series-Parallel Compensated IPT Systems With an Inductive Filter

In the series-parallel (S-P) compensated inductive power transfer (IPT) system for the electric vehicle charging application, an inductive filter is required after the rectifier on the secondary side to avoid the large charging current surge when the diodes conduct. This article proposes a harmonic modeling method for the S-P compensated IPT systems with an inductive filter where both the fundamental and higher order harmonics are considered. Compared to the well-known fundamental harmonic approximation (FHA) method, a more accurate description can be obtained by constructing the circuit model at different harmonics, especially in a strongly coupled case. The zero-voltage switching (ZVS) condition is derived, which shows that a larger load current will cause the power switches to lose ZVS. A larger coupling coefficient will help increase the ZVS range. The output dc voltage will drop slightly due to the high order harmonics, which is different from the FHA method where the output voltage is constant regardless of the load. Experimental results are provided to validate the effectiveness of the proposed harmonic modeling method of the S-P compensated IPT system.