Modeling, Analysis, and Design of Phase Synchronization Loop for BIPT System Considering Operating Point Parameters Variation

In bidirectional inductive power transfer (BIPT) systems, phase synchronization loop that keeps the secondary-side excitation voltage synchronized with the current is essential for stable power transmission. However, the characteristic of control object in the synchronization loop can vary due to the variation of the operating point parameters (OPPs), which can lead to loop instability. In this article, the transfer functions of the control object and the phase detector in the phase synchronization loop are derived. The influence of the variation of OPPs on the transfer function of the control object is analyzed. The transfer function is mainly affected by one zero that is sensitive to the OPPs and can shift into low-frequency region, while the other poles and zeros are at high frequencies and have less influence. The phase synchronization controller is designed considering the variation of OPPs to ensure the stability of the system in a wide range of OPPs. The sensitivity of the loop to the OPPs is analyzed. Frequency response results from simulation and experiment have verified the correctness of the model, and the stability of the loop. Steady-state and transient experiments prove the stable steady-state performance and fast transient response of the system.