Multi-regional modeling and operational analysis of LC/S-compensated inductive wireless power transfer link with load-independent current output

Abstract

When feeding a constant-resistance or constant-voltage type load, inductive wireless power transfer link (IWPTL) operating as current source is typically desired. Moreover, in case coupling coefficient between transmitter and receiver is constant, load-independent current output (LICO) characteristics are beneficial, allowing the system to operate without feedback. Moreover, near zero phase angle (ZPA) operation is also valuable, allowing to minimize volt-ampere rating of the transmitting-side inverter. A new LC/S compensated IWPTL topology, capable of simultaneously achieving LICO and ZPA, was recently revealed in the literature. The proposed compensation network consists of one inductor and two capacitors. This paper generalizes the LC/S compensated IWPTL topology by first deriving the compensating elements set based on a novel loosely-coupled transformer (LCT) equivalent circuit and then enlightening that for certain values of primary compensation inductor, secondary compensation capacitor should either be omitted or replaced by an inductor in order to preserve LICO and ZPA. Thus, an LC/S compensated IWPTL may actually operate in three different regions, each calling for specific sub-type of LC/S compensation. Design guidelines for compensation parameters selection are provided in this paper, allowing to achieve virtually any value of load-independent current output for a given LCT coils pair. Moreover, expressions for calculating normalized component stresses are obtained for all three regions of operation, taking into account nonlinear nature of transmitting-side inverter and receiving-side rectifier, as opposed to typical phasor-domain based approach, which ignores higher-order harmonics. Analytical results based on obtained expressions are well-supported by their real-time-domain counterparts.