Advanced controller design for a series-series compensated inductive power transfer charging infrastructure using asymmetrical clamped mode control

Wireless charging of electric vehicles require a significant air gap between the primary and secondary winding of an inductive power transfer (IPT) system. Due to the existence of the air gap, power flow regulation to keep the output voltage constant becomes a non-trivial task. Hence, the bandwidth, phase margin, and gain margin of the voltage control loops should be appropriately designed, in order to guarantee a robust system. In this paper, a generalized small-signal modelling of series-series compensated (SS topology) IPT system using extended describing function concept has been presented. Using this small-signal model, a controller has been designed for fixed frequency and variable duty cycle, to control the output voltage. Since an asymmetrical clamped mode control (ACM) requires a lower switching frequency compared to the popular fixed frequency control strategies, viz. symmetrical clamed mode control (SCM) and asymmetrical duty cycle control (ADC), it has been used to control the output voltage.