Analytical and experimental investigations of optimal load impedance in LCC-compensated inductive power transfer systems

The optimal AC load impedance (Z_opt) that maximizes the efficiency of an inductive power transfer (IPT) system is investigated analytically and experimentally. A mathematical loss analysis model in which both conduction loss and switching loss are considered is established for active-rectifier-based LCC-compensated IPT systems. By characterizing the full-bridge converter loss using an equivalent loss resistance, analytical expressions of the DC-to-DC efficiency and Z_opt are derived and the influencing factors of efficiency are discussed. Circuit simulations and experimental tests are conducted to quantitatively evaluate the equivalent loss resistance. Several rules regarding Z_opt are derived. Specifically, the necessity of balancing switching loss and conduction loss is demonstrated both analytically and experimentally. The correctness of the loss analysis model is experimentally validated using an electric vehicle inductive charger prototype. The findings provide a solid theoretical foundation and a good initial point for practical maximum efficiency tracking controllers. (C) 2021 Elsevier B.V. All rights reserved.