A Second-order Sliding-mode Controller for Inductively Coupled Power Transfer Systems

This paper presents a second-order sliding-mode (SOSM) control approach for inductively coupled power transfer (ICPT) systems based on zero-current-switching. A second-order dc equivalent model of a series-series (SS) compensated ICPT system is established by replacing its primary side with a dc source and simplifying the rectifier on the secondary side. A SOSM controller implemented by a digital state machine is designed to regulate the output voltage of ICPT systems by controlling the switches on the primary side. Parameters of the controller are derived with a simplified dc equivalent circuit model of the ICPT system. The proposed controller achieves fast dynamic response, robustness against load disturbances and parameter uncertainties without requiring current sensing or any integral terms in the controller. As a result, the output voltage of the system can reach steady state without any overshoots in several switching actions under load disturbances or mutual inductance variations. Simulation results on a 12V/2A system verify the effeteness of the proposed approach.