Coupling Coefficients Estimation of Wireless Power Transfer System via Magnetic Resonance Coupling Using Information From Either Side of the System

Abstract

Wireless power transfer via magnetic resonance coupling method has opened a new possibility to the electric vehicle system. It allows the wireless charging system of moving vehicles, using charging lanes. However, although the efficiency of power transmission is relatively high, the efficiency still depends on displacement of coils. There have been several researches on methods to maintain power transmission at the highest efficiency. However, in such systems, the information on system parameter especially coupling coefficients is needed, and in the charging lane system, such information is unlikely to be obtainable without a communication system. Therefore, it has come to attention that parameter estimation is a crucial factor to implement a charging lane system. This paper presents derivations of equations for estimating coupling coefficients in several configurations of wireless power transfer system, using information from only one side, either the transmitting side or the receiving side, of the system. The presented equations are both applicable to the case of single receiving coil and are also generalized for the case of multiple receiving coils. Each equation is verified by both simulations and experiments. An experimental system of the coupling coefficient estimation system is constructed for estimation from the receiving side using a dc/dc converter.

A Maximum Power Transfer Tracking Method for WPT Systems with Coupling Coefficient Identification Considering Two-Value Problem

“…Energies 2017, 10, 1665 2 of 13 parameters, such as coupling coefficient and load resistance [22,23]. Therefore, in order to achieve MPTT, the identification of these changing parameters is needed previously.…”

“…However, the equations require the information of the resonant currents on primary and secondary sides, which will increase the difficulty in practice. References [22,23] present a dynamical identification method of coupling coefficient, and it only need to measure the parameters on the secondary side. However, it needs to measure the RMS value of alternating currents, which will bring harmonic interference.…”

“…Since the load resistance of a practical WPT system varies with time, therefore using DC/DC converters to do the impedance matching is more suitable for the frequent load variations [19]. However, one thing about the impedance matching using DC/DC converters is that it cannot be realized when unknowing the parameters, such as coupling coefficient and load resistance [22,23]. Therefore, in order to achieve MPTT, the identification of these changing parameters is needed previously.…”

Contactless Power Charger for Light Electric Vehicles Featuring Active Load Matching

“…Given that the coil quality factor dominates the spatial energy transfer, the coil design and associated passive components selection becomes crucial for such CPT system. References [14]- [22] discussed the properties and performance improvement of such systems through detailed modeling, frequency optimization, coil design, and impedance matching. However, high-efficiency power electronic converters that operate in the megahertz range remain a great challenge for magnetic resonance CPT applications.…”

An Approach to Calculate the Efficiency for an N-Receiver Wireless Power Transfer System

“…Researchers have tended to study wireless power transfer systems with a single transmitter and a single receiver. It is clear that the performance of wireless power transfer changes according to factors such as the distance between the transmitter and the receiver [5][6][7].…”