Highly Flexible High-Efficiency Multiple-Resonant Wireless Power Transfer System Using a Controllable Inductor

Abstract

Low- $Q$ resonant converter, such as series–series resonant converter, series resonant converter, and parallel resonant converter (PRC), are highly flexible and highly tolerant to coil misalignments. However, these kinds of topologies cannot be employed to the wide air-gap, low-coupling transformers because of their inadequate magnetizing inductance. On the other hand, high- $Q$ multiple-resonant converters such as series-PRC) and series-SPRC are very suitable for low-coupling compact wireless transformer applications. However, because these multiresonant topologies have several resonant pairs resonating at a single frequency, these parameter values ought to be consistent throughout the operating conditions to resonate at the same frequency. However, since the wireless power transfer (WPT) applications are required to be flexible and convenient to the customers, the wireless transformers are not supposed to be rigid and stationary. To solve the problem, a controllable inductor for a high- $Q$ multiresonant WPT system is proposed to extend the soft switching region and to keep the resonant circulating energy minimum even at resonant mismatch conditions caused by the misalignments or temperature variations of the wireless transformer coils. The performance enhancement of the multiple-resonant wireless converter is validated using the proposed controllable inductor technique, and also the feasibility of the proposed technique is proven under different mismatch conditions through 200-W hardware experimental results.