Decoupled State-Plane Analysis of SeriesSeries Compensated Bidirectional IPT Systems

In series-series compensated bidirectional inductive power transfer systems, the resonant currents are cross coupled due to the influence of multiresonant elements. This makes it difficult to analyze the system behavior using conventional state-plane analysis (SPA) method. To address this challenge, a novel decoupled SPA approach is proposed. It establishes two decoupled equivalent circuits and corresponding state-plane trajectories by decoupling the coupling coil model. Thus, resonant voltages and currents in switching instants can be derived. In addition, the zero-voltage-switching (ZVS) range with different phase shifts and frequency ratios can be determined, and the rms currents of coils can be analyzed quantitatively. To validate the proposed model, a 400-W-rated laboratory prototype is designed and tested. The experimental results align well with the theoretical predictions, and confirm the ZVS among all MOSFETs. The proposed method is universal and can be used to analyze other compensation networks.