Active Impedance Control for Inductive Charging of Light-Duty Electric Vehicles

Designing an inductive power transfer system to deliver constant power over large ranges of lateral and vertical pad misalignment is challenging. Existing power electronic solutions to this problem include duty-cycle control, theta control, and the use of tunable matching networks (TMNs). The disadvantages of these solutions include switch stresses, pad losses, and control complexity. This article proposes a method of tuning and controlling the system known as active impedance control that emulates the behavior of a TMN using fewer components. The method utilizes a novel combination of deliberate mistuning of the secondary compensation network and relative phase angle control to deliver constant power while minimizing converter stresses over a large misalignment range. A mathematical model and search algorithm were developed in order to determine appropriate values for the relative phase angle and compensation elements. A 7-kW system was designed to validate the proposed method. Simulation and experimental results show that the system can deliver near constant power for a 100% change in mutual inductance with a constant battery voltage, and a maximum dc-dc efficiency of 92.7% was achieved.