Design Recommendations Considering Charging Pads’ Self-Inductance Variation With LCC–S and LCC–LCC Compensation Based IPT Chargers in Low Clearance EVs

Inductive power transfer (IPT)-based electric vehicle (EV) charging systems practically experience self-inductance variation in charging pads with air-gap, especially for low ground clearances. The conventional design model ignores these variations, resulting in poor sizing and performance. This article presents a comprehensive theoretical modeling and evaluation of the system’s performance considering self-inductance variation for LCC-series (LCC-S) and LCC–LCC type compensation. The work begins by examining various types of charging pads with similar design specifications, and finds circular-pad to exhibit the least self-inductance variation. Subsequently, through extensive theoretical analysis, several contour plots are derived, depicting the variation of output voltage/current, output power, input volt-ampere (VA), input power factor, and VA of compensation elements with various load and coupling-coefficient, for both the conventional and proposed models systematically. It is shown that the proposed model provides accurate design recommendations over the conventional model on various critical parameters, including optimal load, charging time, dc-link voltage, the maximum gain of secondary-side dc–dc converter, and VA ratings of the input and compensation elements. For example, the proposed model predicts that a 7% increase in self-inductance with LCC-S type compensation (designed for 5 kW) leads to a 36.4% reduction in maximum output power, requiring compensatory increases in dc-bus voltage by 25.3% and input VA rating by 34.47%. The proposed model is validated experimentally.