Dynamic Improvement of Sub-Resonant Frequency Control for Inductive Power Transfer Systems by Coupling Estimation and Sending-Side Gain-Scheduled Control

This article presents a sending-side gain-scheduled controller for improving the dynamic response of Inductive Power Transfer (IPT) systems with sub-resonant frequency control. The presented method is intended for inductive battery charging in high-power transport applications which are required to operate under highly variable conditions, including a wide range of coupling and output power. For such applications, the use of fixed controller gains selected to ensure the system stability in the full range of operation causes a slow response under low coupling or light load conditions. For implementing the gain-scheduling, the output power and coupling coefficient of IPT systems with the sub-resonant frequency control are estimated in real-time by using only sending-side information. The parameters of the gain-scheduled controller are then determined by the output power value and the estimated coupling, to ensure the rapid response and stability of the system. Moreover, the bandwidth limitations and risks of instability caused by dual-side communication in closed-loop power control is avoided. Effectiveness and feasibility of the proposed method are validated by time-domain simulations and experimental results from a small-scale laboratory prototype.