Analytical Evaluation of Loss Reduction With ZPA Over Full ZVS Operation for Bidirectional WPT System

The enhancement of efficiency in bidirectional wireless power transfer (BWPT) systems depends on minimizing losses occurring in the coils and high-frequency (HF) converters. Circuit impedance optimization through zero-phase-angle (ZPA) operation is essential to address coil losses. However, turn-on switching losses of ground and vehicle assembly (VA) converters are reduced by operating under full zero voltage switching (FZVS). However, the existing literature lacks thorough research that quantifies and compares the loss reduction with the ZPA or FZVS across various operating conditions to maximize the efficiency of BWPT systems. This article comprehensively analyzes the BWPT system losses, incorporating ZPA and FZVS operating conditions. It provides mathematical conditions for achieving FZVS operation across a broad range of misalignments and varying load conditions. The article also evaluates losses and efficiency in varied loading and misalignment scenarios for ZPA and FZVS, deriving optimal operating conditions to maximize system efficiency. The comparative analysis is performed on a 1-kW series-series (S-S) compensated BWPT system, and the findings are supported by experimental and simulated results.