Wireless Power Transfer to Multiple Loads Over Various Distances Using Relay Resonators

Abstract

Resonant wireless power transfer has attracted much attention in recent decades. In some practical applications such as wireless sensor networks, multiple-load transfer over various distances is required. In this letter, the intermediate-coil structure is utilized to transfer the same power to multiple loads over various distances, which indicates that the intermediate coils work both as relay resonators and as power receivers. The mathematical model is built and in-depth analysis is conducted. Four important factors, namely the source matching factor, the load matching factor, the transfer quality factor, and the reflected impedance factor, are employed to build the mathematical model of -load transfer. The conditions to transmit the same power to all the loads attached in each relay resonator are investigated. The optimal load resistance and the highest efficiency with the same load resistance are derived. The theoretical calculations and the experimental results of double-load and three-load transfer confirm the analysis.Index Terms-Intermediate coils, magnetic resonance, multiple loads, relay resonators, wireless power transfer (WPT).

Multiple receivers wireless power transfer systems using decoupling coils to eliminate cross-coupling and achieve selective target power distribution

“…As the conventional single-transmitting (Tx) and single-receiving (Rx) circuits cannot fulfil the requirement of simultaneously providing power for multiple electrical devices in practical applications, the study on multi-Rx coils has made great progress in recent years [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. For multi-Rx coil systems, the cross-coupling between the coils cannot be ignored when Rx coils are very close to each other.…”

“…Some researchers used the different frequencies to distinguish the Rxs [15,16,17], which makes the power distribution at the receiving Rx side selective. In [18], the author analysed the energy transmission direction of multiple coils on the same axis, of which each coil gets the same power by adjusting the distance between the coils. To control the load power of the Rx coil at a fixed distance, K. Ean et al explored the power distribution method of using impedance inverter on the Rx side of single-Tx and multi-Rx system [19].…”

“…However, the parameters of impedance inverter were affected by other Rxs. Unlike most multi-Rx WPT systems [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], this study proposed WPT system that eliminates the energy multipath effect and distinguishes the multiple Rxs to realize one-toone transmission energy in single-frequency, which helps to achieve selective target power distribution. The proposed system can be used in battery charging applications to increase system efficiency, because it can prevent the power supply to fully charged devices by selectively not transmitting power to the target receiver [16].…”

“…By adjusting the parameters of the impedance inverter, multiple loads can get the same power. Therefore, the system can also be applied to practical applications such as chain wireless sensor networks that need to supply the same power to multiple loads at different distances [18].…”

Power Control Strategies of On-Road Charging for Electric Vehicles

“…Reference [20] investigates the effect of multiple devices on the WPT system efficiency. Reference [21] utilizes an intermediate-coil structure to transfer the same power to multiple loads over various distances. Reference [22] investigates an impedance matching method of providing adjustable power distribution among receivers.…”