Modeling and Decoupled Control of Inductive Power Transfer to Implement Constant Current/Voltage Charging and ZVS Operating for Electric Vehicles

To prevent the degradation of battery life and reduce switching loss in inductive power transfer (IPT) systems for electric vehicles (EVs), it is vital to realize constant current/voltage (CC/CV) charging and zero-voltage-switching (ZVS) operation. However, due to the existence of couplings between the charging and ZVS operating control loops, the controllers are neither optimal nor robust. In this paper, a model-based decoupled control method is proposed to improve the performance of the charging and ZVS operating controllers. Since the operating point of the CC and CV modes are different, two dynamic models for the corresponding charging modes are built and linearized. Besides, the couplings between the charging and ZVS operating control loops are analyzed, and in turn, decoupled by designing compensators. To optimize the system performance, we chose PI controllers, and their parameters are obtained by calculating the settling time and overshoot of the close-loop dominant poles according to the control performance requirements. In the experiment, a 500-W series-series IPT system prototype is built and tested to verify the improvement of the control performance. Compared with the coupled control method and the traditional closed-loop control feedback method, the recorded response curves and transient waveforms demonstrate that the proposed decoupled control method brings a better performance to the system.