Automatic tuning concept for a three-phase inductive power transfer system

Contactless charging of electric vehicles by means of inductive power transfer is becoming increasingly popular in the recent years. In contrast to wired power interfaces, user-friendly and secure wireless links with no physical contact are preferable. Especially in the higher power range (>100kW), three-phase approaches are an encouraging alternative to single-phase systems due to great EMC benefits. While compensation of single-phase systems is comparatively simple, the static tuning procedure is much more complex for three-phase systems. Aggravating, system parameter drifts arising from slightly mismatched positioning and thermal influences shift the systems current working point away from the optimal one for which the whole system is tuned statically. As an essential base, in a first part this paper introduces an appropriate approach for the static tuning of a three-phase system and discusses the effects of parameter drifts on the pickup. Based on the static tuning, concept ideas for an automatic retuning of the pickup during operation are presented in the second part.