Tuning Control Against Coupler Parameter Variations Due to Misalignment in an Optimal-Efficiency-Tracking and Constant-Power-Output IPT System

Abstract

In inductive power transfer (IPT) systems, air gap variations can cause fluctuations in the parameters of the loosely coupled transformers (LCT), potentially compromising resonant tank performance, output stability, and transfer efficiency. To address this issue, this article introduces a novel multiloop control strategy for a single-stage power-source IPT system. Specifically, the proposed system replaces traditional compensation capacitors with switch-controlled capacitors on both sides and incorporates a semiactive rectifier on the secondary side. On this basis, a control strategy is identified and implemented with three loops, including a secondary tuning loop using a gradient descent method to counteract coupler parameter variations due to misalignment, a load matching loop for tracking optimal efficiency and a primary-side input impedance tuning loop for maintaining constant power output. This strategy maintains optimal efficiency and constant power output despite dynamic variations in LCT parameters, coupling coefficients, and load conditions. Notably, it eliminates the need for direct detection of LCT self-inductance and mutual inductance parameter variations. Furthermore, the system operates at a fixed frequency and achieves zero-voltage switching, enhancing overall efficiency. Finally, a 500 W experimental setup is established to validate the feasibility and effectiveness of the proposed system.