Analysis and design of a contactless power transmission system based on the extended first harmonic approximation

For the task of transferring energy inductively, resonant converters are a suitable family of converters in order to overcome the technical hurdle of the loose magnetic coupling that is often encountered in this kind of application. However, the analysis of resonant converters is in general cumbersome. In order to facilitate the design process where a vast number of converter configurations has to be computed, approximations are required in order to bring the necessary computational time to maintainable levels. A design procedure for a contactless power transmission system based on the extended first harmonic approximation for the steady-state solution of the multi-resonant LLCC converter is presented in this paper, with a new degree of simplification regarding the resulting closed-form solution. By means of this approximation, the design of the fourth-order resonant LLCC converter is significantly simplified, providing a tool for rapid simulation combined with a very high accuracy. The resulting system was designed to be very tolerant against variations of the distance between the coils, at the same time achieving a very high efficiency for this kind of application.