A Cascaded Topology and Control Method for Two-Phase Receivers of Dynamic Wireless Power Transfer Systems

In a dynamic wireless power transfer (DWPT) system for electric vehicles, bipolar transmitting rail is often implemented to improve the misalignment tolerance, but its constraint often lies in fluctuating output. This problem can be mitigated by applying two-phase receivers which, due to its structural characteristics in the impedance matching circuit, bring two new problems: limited range of impedance matching and low efficiency. This paper aims to tackle the two problems by introducing a cascaded topology and its control method. Firstly, the conventional topology of the two-phase receiver is thoroughly analyzed theoretically concerning impedance matching range and efficiency model. Secondly, a cascaded bridgeless rectifier-Buck (CBRB) as impedance matching with $0\sim \infty \Omega $ matching capabilities is put forward. Besides, the independent two-channel structure is also introduced leaving the output current ratio the key to efficiency optimization. Thirdly, the control method for the proposed topology using heuristic current ratio by adopting online estimation via auxiliary measurement coils is presented. Finally, experiments are verified on a 20 kW DWPT platform and the proposed topology and control method can raise the transfer efficiency by 3.3% compared with the conventional topology.