Synthesis and Analysis of Primary High-Order Compensation Topologies for Wireless Charging System Applying Sub-Harmonic Control

Subharmonic control (SHC) is an excellent method for wireless charging system because it is easy to achieve full-load range soft switching and unity power factor. However, in existing works, SHC is only applied to the system with primary series compensation topology, which has the drawbacks of low degrees of design freedom, high sensitivity to misalignments and no open-circuit protection. To overcome these issues, in this article, systematic synthesis of primary high-order compensation topology (PHCT) for WPT is identified in terms of general T-branch structure. Afterward, the applicability of PHCT to SHC is explored by gaining insight into their filter characteristics. It reveals that when SHC is applied, four kinds of PHCTs are superior over other candidates in performance because the unity power factor and soft switching can be achieved without limitation on pulse distribution. Then, six kinds of PHCTs exhibit a moderate performance as they may nullify the strengths of SHC under some specific pulse distributions. The rest of PHCTs are not applicable to SHC no matter what the pulse distribution. Finally, the experimental results on prototype with jointly applying SHC and PHCT are examined.