Effect of Misaligned Relay on Output Power and Efficiency in Wireless Power Transfer

Abstract

In magnetic resonance-based wireless power transfer (WPT), any misalignment between resonators degrades the strength of the magnetic coupling, and the use of a relay does not always improve performance if it is misaligned with a transmitter or a receiver. It is therefore necessary to determine the proper activation of a relay depending on the degree of misalignment. In this paper, we analyze the effect of a misaligned relay on two important performance metrics in WPT, namely output power and efficiency. In particular, we derive the achievable output power and efficiency with optimal load resistance based on an equivalent circuit model, and determine whether it is beneficial to utilize the relay for a given lateral and angular misalignment. By simulation and experimental verifications under various environments, we validate the exactness of our analysis, and we also confirm two interesting observations, namely 1) with regard to performance improvement in terms of output power and efficiency, it is better to deactivate the relay if it is seriously misaligned with the other resonators and 2) output power is more vulnerable to the misalignment of a relay than efficiency.INDEX TERMS Wireless power transfer, magnetic resonance, misalignment, relay activation, output power, efficiency Recently, the use of relays has been considered for WPT in order to improve both the system efficiency and the operating distance [22]-[27]. Specifically, the optimal impedance matching and improved stability using an intermediate relay were analyzed [22], [23], and an optimal configuration of

On the Design of Magnetic Resonant Coupling for Wireless Power Transfer in Multi-Coil Networks

“…Aiming to maximize the information capacity of MRC communications, the authors in [6], investigate both the strongly and loosely coupled regions and define the optimal parameters which provide high information capacity. A system supported by a relay-acting coil is investigated in [7], where the effect of lateral and angular misalignment is captured. In [8], the authors consider a WPT system with a single transmitter and multiple receivers and characterize the "near-far" fairness issue, which occurs from the distance-dependent mutual inductance with the transmitter.…”