Design of Asymmetrical Relay Resonators for Maximum Efficiency of Wireless Power Transfer

Abstract

This paper presents a new design method of asymmetrical relay resonators for maximum wireless power transfer. A new design method for relay resonators is demanded because maximum power transfer efficiency (PTE) is not obtained at the resonant frequency of unit resonator. The maximum PTE for relay resonators is obtained at the different resonances of unit resonator. The optimum design of asymmetrical relay is conducted by both the optimum placement and the optimum capacitance of resonators. The optimum placement is found by scanning the positions of the relays and optimum capacitance can be found by using genetic algorithm (GA). The PTEs are enhanced when capacitance is optimally designed by GA according to the position of relays, respectively, and then maximum efficiency is obtained at the optimum placement of relays. The capacitance of the second resonator tonth resonator and the load resistance should be determined for maximum efficiency while the capacitance of the first resonator and the source resistance are obtained for the impedance matching. The simulated and measured results are in good agreement.

Method for Estimating Optimum Free Resonant Frequencies in Overcoupled WPT System

“…In addition, the system energy efficiency was used to express the PTE instead of the more commonly used transmission efficiency. On the other hand, the free resonant frequency tuning method was applied not only to the two-coil WPT system but also to the multicoil WPT system [14]. The authors of [14] determined the capacitance and free resonant frequencies by using a genetic algorithm; however, the process does not guarantee a global maximum and takes dramatically increasing time as the number of resonators increases.…”

“…On the other hand, the free resonant frequency tuning method was applied not only to the two-coil WPT system but also to the multicoil WPT system [14]. The authors of [14] determined the capacitance and free resonant frequencies by using a genetic algorithm; however, the process does not guarantee a global maximum and takes dramatically increasing time as the number of resonators increases. Additionally, it is also cumbersome to apply the principles used in [13] to the multicoil WPT system.…”

Wireless power transfer using relay resonators

“…For capacitive coupling, energy is trans-40 ferred through an electric field, the quantity of energy 41 transferred being directly proportional to the frequency. 5,6 42 For medium range applications, the transmitter-receiver dis-43 tance varies between one to ten times the diameter of the 44 transmitter coil with an operational frequency range of 45 10 kHz-200 MHz. An inductively coupled system using mul-46 tiple coils as advantages over other systems (non-multiple 47 coils) by the extension of the power transfer distance 48 between the transmitter to receiver.…”

“…The coupled magnetic 49 resonance system (CMRS) and inductive power transfer 50 method are forms of the medium ranged applications. 5,6 The 51 MIT research group described the detailed working principle of CMRS system. 7 This radiative type is known as far-field power transfer.…”

“…6 There have been several studies over the last few years to enhance the efficiency of the WPT system for short, medium, and long distances using relay resonators between the transmitter and receiver coils. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] For example, Choi and Lee 5 investigated the optimal position of relay coils from the tested measured results without verifying the experimental results with theory or simulation. In another paper, Ahn and Hong 3 demonstrated the WPT for multiple loads over various distances and verified the optimum conditions with measured results.…”