Multi-Objective Optimization Design of a Three Coil Wireless Power Transfer System for Electric Vehicle Charging

Abstract

This work sets forth an evolutionary optimization framework for three-coil wireless power transfer (WPT) systems based on resonant repeater coils, aimed at addressing the growing demand for high-performance and autonomous electric vehicle (EV) charging solutions. While conventional two-coil systems are constrained by limitations in efficiency, power density, and misalignment tolerance, the proposed three-coil architecture enhances electromagnetic coupling through the inclusion of an intermediate resonator.
A simplified T-equivalent circuit for the system is introduced and used to analyze the influence of the intermediate coil on power transfer characteristics. It is shown that full series compensation, although effective in two-coil systems, may induce reactive imbalance in three-coil topologies. To that end, a partial compensation strategy is formulated to improve performance and maintain resonance alignment.
Building on this analytical foundation, a multi-objective optimization framework is developed by integrating finite element analysis (FEA) with a genetic algorithm (GA) to co-optimize coil geometry and compensation parameters under practical constraints. A 1 kW prototype selected from the Pareto front is fabricated and experimentally validated, achieving 90.22% DC–DC efficiency and 10.71 kW/m2 power density. Experimental results match simulation within 2.7%, affirming model accuracy and compliance with electromagnetic safety standards.
The framework is then applied to a 30 kW configuration representative of high power EV charging, with both two- and three-coil architectures studied under identical constraints. Comparative analysis shows that the three-coil system consistently outperforms its two-coil counterpart across the Pareto front, reaffirming its suitability for next-generation high-power WPT applications.

Date of Award	2025
Original language	American English
Supervisor	Jamal Alsawalhi (Supervisor)