Simultaneous control of transmission efficiency and power at time-varying loads in WPT systems

Wireless power transmission (WPT) is a method of transmitting power wirelessly and has attracted much attention in recent years because of its advantages such as the absence of connections and the ability to ignore obstacles. The magnetic field resonant coupling method that we have adopted is one of the most robust among WPT methods in terms of misalignment between coils, and is capable of transmitting large amounts of power. However, WPT has a problem that transmission efficiency and transmission power decrease due to parameter fluctuations such as load changes. Therefore, we propose a control scheme for time-varying output load resistance. In this paper, we model a WPT system and show how to find solutions to the second-order differential equation for output voltage under time-varying loads. Furthermore, a control system that simultaneously controls power and transmission efficiency under time-varying load is presented, and finally, simulation results and experimental results using actual equipment are presented.