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.

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