A Hybrid Mode Control Strategy for LCC-LCC Compensated WPT System with Wide ZVS Operation

In this paper, an efficiency-oriented control strategy is proposed for LCC-LCC compensated Wireless Power Transfer (WPT) system to achieve zero-voltage-switching (ZVS) operation over a wide current regulation range, in which full-bridge (FB) and half-bridge (HB) modes are combined and switchable based on requirements from load. The harmonic-considered time-domain models for FB and HB modes are firstly built to calculate current through the switches at the turn-off moment accurately. Then, focused on the CV charge stage with variable output current, the ZVS boundaries are identified in HB and FB modes as the preferable control trajectories, which determines the desired current output with joint considerations of frequency, phase shift angle, and duty ratio. Next, an least squares (LS) optimization method is introduced to fit the threoretical control trajectories into a smooth curve that is practical for implementation on microcontrollers. Finally, a 4.4-kW WPT prototype is built to verify feasibility and validity of the proposed control strategy. Results show that a high system efficiency can be achieved over a wide output current range, with an efficiency of 94.68% even at 20% rated power.