Combined Frequency and Phase-Shift Control for Constant-Voltage Charging Mode of Wireless Power Transfer System in AGV Applications

The wireless power transfer (WPT) application for the industrial sector becomes a common technology in recent years. The number of WPT products continues to increase and the maturity is increasingly promising. Hence, the improvement in terms of the power efficiency becomes a big concern for the real implementation, such as in the automated guided vehicle (AGV) applications. In this paper, a new control strategy is proposed to compete with the conventional ways. The invention is derived by combining the widely-used frequency modulation (FM) and phase shift modulation (PSM) strategies. Therefore, the operational ways are discussed firstly, then followed by the mathematical derivation for the proposed control strategy. The limitation of the proposed method is also listed in this paper, as well as the solution to overcome it. To provide a good proof of this method, a real hardware prototype is experimentally tested in the FM, PSM, and the proposed control strategies. The WPT system is constructed in the series-series (SS) topology with the constant voltage (CV) charging mode condition due to the popularity and simplicity. However, the proposed control strategy is also suitable for the other WPT resonant topologies. Finally, the captured waveforms show that it can achieve the power transfer efficiency up to 88.45% in 300W, which is higher than the results from the other conventional control methods.