Analysis and Design of Multifrequency Compensation Strategy for Wide Misalignment Tolerance in Inductive Power Transfer Systems

Abstract

In inductive power transfer systems, misalignment can lead to inconsistent output power. In this paper, a topology based on a primary-side detuned multi-frequency compensation circuit is proposed to provide consistent output over a wide misalignment range. This topology exhibits multiple intersecting power vs. coupling coefficient curves given multiple switching frequencies. The coupling range, and associated misalignment range, can be extended without increasing power and current variability by changing the switching frequency strategically at curve intersections. Parameter design and selection of the number of switching frequencies are presented. Fundamental relationships between power variation and coupling range are established. With this approach, a choice of two suitable switching frequencies changes output power by only 10% over a coupling coefficient range from 0.14 to 0.35. Three frequencies can support lower power variation or a wider coupling range. Primary current at low coupling is lower with the strategy than for conventional alternatives because reactive power can be limited. A 1.5 kW prototype has been prepared to verify the topology. The prototype confirms power variation of 10% over a coupling coefficient range from 0.14 to 0.35 with two frequencies. With three frequencies, power variation drops to 6.7% over the same coupling range.