Compensating Propagation Delay in PT-Symmetry-Based Inductive Power Transfer Systems: Control Strategies for Misalignment-Tolerant CC and CV Operations

The output of inductive power transfer (IPT) systems typically depends heavily on the load resistance and the coupling conditions of the inductive coupler. In this article, we implement variable frequency control and phase-shift control to enhance misalignment tolerance and regulate the IPT system’s output, achieving constant-current (CC) and constant-voltage (CV) operation to meet battery-charging requirements without communication between the primary and secondary sides. In CC mode, parity-time (PT)-symmetry-based frequency control is employed, and a dynamic compensation method is proposed to counteract phase delay in the control loop, thus achieving the negative resistance needed for PT-symmetry. With phase-shift control, the output current amplitude can also be regulated. In CV mode, a primary-side-only coupling estimation method is developed to determine the operating frequency and inverter duty cycle for CV operation. Ultimately, the proposed IPT system consistently delivers a 5-A output current in CC mode and a 46-V output voltage in CV mode, regardless of transmitter–receiver coil position, with a system efficiency ranging from 80% to 95%.