Phase Synchronization of Control Signals Based on Perturbation and Observation for Bidirectional Wireless Power Transfer System

Abstract

For the bidirectional wireless power transfer (BWPT) system, when both the primary and secondary converters become active, the phase synchronization between their control signals are necessary to control the power flow direction. Generally, the synchronization is realized by the real-time wireless communication devices or the auxiliary windings, which calls for high requirements of the hardware for sampling and controlling as well as increases the cost. Therefore, this paper proposes a new phase synchronization method without the real-time communication or auxiliary hardware. Firstly, the relationship between the output current and the phase differences of the control signals is derived. It is found that the extreme value of the output current is determined by the relative phase-shift angle between the primary and secondary converters and the internal phase-shift angles of the two converters. Secondly, a scheme for generating the control signals is proposed to ensure that the relative phase-shift angle is not influenced by the internal phase-shift angles. Thirdly, based on the perturbation and observation method, a procedure is proposed to track the extreme value of the output current and obtain the target relative phase-shift angle for the phase synchronization state. Finally, simulation and experimental results verify the validity of the proposed method. The method is easy to be implemented, and useful for the bidirectional power flow of the static BWPT system.