Reconfigurable Coil Array for Near-Field Beamforming to Compensate for Misalignment in WPT Systems

Abstract

This work develops a reconfigurable coil array that compensates for the misalignment between coils in magnetic resonance coupled wireless power transfer (WPT) systems. By tuning the magnitude of the currents induced in the coil array with the variable capacitors that load them, the effect of reconfiguring the size and/or shape of the coil can be achieved. Therefore, the near field can be steered in a certain direction to overcome the notorious misalignment problem in WPT systems. For experimental demonstration, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 1$ </tex-math></inline-formula> array is designed and fabricated for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$60\times 60$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> coil. For a vertical distance between Tx and Rx coils of 10 mm, which is 16.7% of the largest coil dimension, the transfer efficiency maintains more than 40% and up to 141.6% misalignment. This is more than an 81% increase over the conventional coil. For a vertical distance of 30 mm or 50%, the minimum transfer efficiency is 37.1% up to 100% misalignment, which is almost 5.5 times that of the conventional counterpart. The results suggest that the demonstrated technology successfully overcomes the notorious misalignment problem in both short-range and midrange WPT systems and even in asymmetric systems where the reconfigurable coil array technique is applied only on the Rx.