Secondary-side-only Phase-shifting Voltage Stabilization Control with a Single Converter for WPT Systems with Constant Power Load

In recent years, wireless power transfer technology has received considerable attention because of its wide range of applications. Most of the literature focuses on the resistance load or constant voltage load, and the constant power load is almost never considered. The open loop transfer function of a constant power load is unstable, and therefore closed loop stabilization is required. Furthermore, communication between the two sides is often used but it may not be available. In order to stabilize the load voltage without resorting to coordination with the primary side and discontinuous operation causing big voltage transients, this paper proposes a control strategy for only the secondary side using a single converter. It is based on the combination of synchronous rectification and symmetric phase shift, without communication with the primary side. While the primary side is not manipulated, the AC/DC converter regulates the amplitude of the secondary coil voltage and stabilizes the constant power load voltage on the DC side via a simple PI control. In this paper, the control concept, design and stability analysis are provided. The proposed control is verified through experimental results in both static and dynamic scenarios, achieving a controller that is simple to design and has smooth waveforms.