Robust Wireless Power Transfer by Self-Oscillating Controlled Inverter and Tripolar Receiving Pad

Stable power transfer with constant and high transfer efficiency to moving devices is a major challenge in wireless power transfer (WPT). The amount of transferred power and efficiency is sensitive to magnetic coupling coefficient variations. Many control methods based on continuous analysis of WPT systems have been proposed to ensure stable and optimal power transfer between transmitter and receiver in variable magnetic coupling conditions. This paper presents a robust WPT system to coupling coefficient variations using a self-oscillating controlled inverter without any communication link between the transmitter and receiver and other auxiliary control circuits. In this research, the receiving tripolar pad (TPP) is used with this type of inverter for the first time, providing an improved robust WPT to charge electric vehicles. At air gaps between 10 and 29 cm, and long ranges of lateral misalignments, the output power is approximately 1000 watts with a difference of less than 20%, and the system efficiency is higher than 92%. In rotational displacements, efficiency remains high with output power variations around 1000 watts with a difference of less than 40%. Thus the proposed system automatically provides an almost constant output power with high efficiency in a certain range of displacements and misalignments of the receiving pad.