A Study of a Novel Optimization Method for IPT Systems with Variable Frequency

Inductive power transfer systems are widely used in various applications, which increases the demand on improving their efficiency to avoid the energy waste. As a result, there is increasing research interest in the optimization methods to maximize their efficiency. While most of the existing optimization methods focus on fixed frequency systems this paper presents an optimization method for variable frequency systems. The method aims to maximize the average DC-DC efficiency across the whole load range by adjusting the coupling coil geometry and the input DC voltage. Special interest is paid to the implementation of variable frequency regulation in a microcontroller, which provides only discrete frequencies and thus may render the regulation unstable. The presented method is implemented in MATLAB using the Global Optimization Toolbox and the FEMM software package. The method is verified by a design of a Qi inspired wireless charger for a rocket. A constructed prototype provides constant output voltage of 30 V and up to 35 W of the output power. Its DC-DC efficiency has a maximum of 82.2 % and an average of 74.8 % for output power above 5 W.