Operating characteristics of four‐coil magnetic resonant coupling wireless power transfer under different resonant states

Abstract

In wireless power transfer, the transfer efficiency decreases with the increase of the transfer distance. To improve the power transfer performance, the operating characteristics of a conformal coplanar four-coil magnetic resonant coupling wireless power transfer system are investigated and analyzed under four different resonant states. Based on the complete equivalent circuit model, the transmission coefficient and the input impendence are calculated. The performance of the systems operated under four resonant states is studied and compared. Also, the origin of the difference is specifically analyzed. The simulation results indicate that the wireless power transfer system operated under State 1, the state where the compensated serial capacitance makes the coils work at the frequency of the maximum Q-factor, shows the most excellent transfer characteristic among the four resonant states. The transmission coefficient can be well maintained above 0.8 within the transfer distance of 30 cm. Experiment has been carried out for validation, and the result indicates that more power can be delivered to the load for the system operated under State 1. K E Y W O R D S operating characteristics, resonant state, transmission coefficient, wireless power transfer 1 | INTRODUCTION Wireless power transfer has received a great deal of attention as it provides a possibility to deliver energy without power lines. A variety of wireless power transfer techniques have been developed, which are based either on near-field or farfield electromagnetic coupling. 1,2 Previous studies have demonstrated that higher power transfer efficiency can be obtained via the near-field techniques than the far-field approaches. In the near-field techniques, compared with the traditional inductively coupled scheme, magnetic resonant coupling wireless power transfer (MRC-WPT) has been a hot research area due to its longer transfer distance. 3 Thus, it is applied in various applications such as implanted biomedical devices, portable electronics, and electric vehicle charging system. 4-6 Generally, most MRC-WPT systems are featured with two coils. It has been revealed in other studies 7-9 that the transfer performance of the two-coil system deteriorates with the increase of the transfer distance due to the weakened magnetic coupling. To extend the transfer distance, MRC-WPT systems with repeaters positioned between transmitting and receiving coils have been investigated. 10-15 Nevertheless, the transmission efficiency

Two‐port network compact representation of resonator arrays for wireless power transfer with variable receiver position

“…with Ẑið1,2Þ the element of the first row and second column of (11). Analogously, for the calculation of Ẑ11 and Ẑr1 , an impedance Ẑload is connected to the output port so that c V r ¼ À Ẑload Îr .…”

“…In order to improve the tolerance to the misalignment, arrays of magnetically coupled resonating L-C circuits (also referred as relay coils) can be used, which represent a very cheap solution since only few passive electronic components are required. [7][8][9][10][11] In these systems, the power travels from the source to the load through the relay coils at the expense of an increased sensitivity to the mismatch between the input and output side impedances, 12,13 which reflects also on the magnetic near-field distribution. 14 Solutions to this problem have been proposed in Sandoval et al, 15,16 making arrays of…”

Enhancement of robustness to frequency detuning with wireless power transfer based on Van der Pol resonance

“…[1][2][3][4][5] For near-field power transfer, magnetic coupling resonance wireless power transfer (MCR-WPT) is preferred due to its effective wireless exchange of electromagnetic energy, and the power can be transmitted to a relative longer transfer distance. [6][7][8][9][10] In the MCR-WPT system, power efficiency is an important factor for estimating performance of energy transmission. [11][12][13][14][15] In the previous research, it has been pointed out that the quality factor of the MCR-WPT system should be kept at a relatively high value so as to keep high power efficiency.…”

“…Wireless power transfer has been an area of interest in a variety of applications such as charging of electric vehicle battery, wireless sensor networks, drone power supplies, portable electronics, and implantable biomedical devices 1–5 . For near‐field power transfer, magnetic coupling resonance wireless power transfer (MCR‐WPT) is preferred due to its effective wireless exchange of electromagnetic energy, and the power can be transmitted to a relative longer transfer distance 6–10 …”

Novel compact coupled resonator wireless power transfer system at 1 GHz using nested open loop ring resonators

“…Three 5.8 GHz rectennas are presented using a capacitively coupled circular patch antenna (rectenna1), a two‐element linear array (rectenna 2), and a four‐element array (rectenna 3) for WPT applications 25 . The work in Wang et al 26 is improved the power transfer performance, the operating characteristics of a conformal coplanar four‐coil magnetic resonant coupling WPT system. The article in Lin et al 27 is presented a resonant topology design method for implantable WPT system, by which a series of WPT topologies are proposed.…”