Extended Constant Output Region of CPT System With S-LCC Compensation Based on Generalized Parity-Time Symmetry

In the existing capacitive wireless power transfer (CPT) systems based on the parity-time (PT) symmetry principle, the stable transfer characteristics are limited by the critical coupling coefficient, and the system's topological structure has to be strictly symmetric to satisfy the PT symmetry requirements. Therefore, this article proposes a novel CPT system with an S-LCC compensation structure based on the generalized parity-time (GPT) symmetry. As a general form of PT symmetry, GPT symmetry has broader applicability. Through equivalent circuit analysis, the S-LCC structure is equivalent to an S-S circuit, and the system characteristics are obtained by combining the simplified approximation method. On this basis, the error of the proposed method is analyzed, and the impact of system parameters on output characteristics is analyzed and compared with the PT-based CPT system. Meanwhile, the stability of the proposed system is analyzed using the describing function method (DFM). Finally, a 20W experimental prototype is built to verify the feasibility of the proposed system, and the experimental results are consistent with the theoretical analysis. Compared with the PT-based CPT system, the critical coupling coefficient of the proposed system decreased by 62%, indicating that the constant output region is significantly improved.