Active Impedance Control for Inductive Charging of Electric Vehicles

Misalignment of pads and the charging and discharging of the electric vehicle (EV) battery makes delivering constant power with an inductive power transfer (IPT) system non-trivial. One solution is to add Tunable Matching Networks (TMNs), which are essentially variable reactances, in between the converters and compensation networks. However, TMNs are costly to implement. As an alternative, this paper proposes a method of tuning and controlling the system known as Active Impedance Control (AIC) that emulates the behaviour of a TMN. Mathematical modelling was used to design an AIC system that can transfer 7.7 kW of power with near unity power factor under a 2.35-fold change in induced voltage for a constant battery voltage. Additionally, rectifier input current varies by only 1.4 times across the operating range. Furthermore, simulation results show good agreement with the mathematical model.