A Novel All-Direction Antimisalignment Wireless Power Transfer System Designed by Truncated Region Eigenfunction Expansion Method

Abstract

This article proposes a novel wireless power transfer (WPT) system, which achieves high misalignment tolerance in all directions by using antiparallel windings. The transmitter coil is composed of two parts of wires wound in opposite directions; thus, the magnetic flux with different directions would counteract partly. With the properly designed parameters, the mutual inductance between transmitter and receiver coils could remain constant when misalignment occurs. Therefore, the output power and the efficiency of the system can remain unchanged. Moreover, this article proposes a novel analytical calculation method for mutual inductance based on the truncated region eigenfunction expansion method, which greatly promotes and simplifies the design process of a magnetic coupler. This method solves the problem of mutual inductance calculation with a finite ferrite substrate. Factors that influence the mutual inductance of circular coils are systematically studied based on the method. Finally, an experimental prototype is built to verify the validity of the system. The mutual inductance can remain 97% of the well-aligned value within a 0.1-m misalignment, and the overall efficiency is consistently higher than 90.2%, while the fluctuation of the output power is within 3%.