A Primary-Side Gain-Scheduled Controller Based on Dynamic Coupling Estimation for Inductive Battery Charging Systems with Sub-resonant Frequency Control

Inductive power transfer (IPT) systems in high-power transport applications are often required to operate under highly variable conditions, including a wide range of coupling and output power. For classical controllers, a fixed gain is selected to ensure the system stability in the full range of operation, which poses a challenge to the dynamic performance of the system with different working conditions. This paper presents a primary-side gain-scheduled controller for inductive battery charging systems with the sub-resonant frequency control to significantly improve the system dynamic response. The output power and dynamic coupling of IPT systems with the sub-resonant frequency control are estimated in real-time by using only the information on the primary side. The parameters of the gain-scheduled controller are then determined by the power reference value and estimated coupling, to ensure the rapid response and stability of the system. Moreover, the risk of instability and failure caused by dual-side communication in closed-loop power control is avoided. Effectiveness and feasibility of the proposed method are validated by simulation and experimental results from a small-scale laboratory prototype.