A Novel Method of Coupling Coefficient Estimation for a Series-Series Wireless Power Transfer System

In wireless power transfer systems, many parameters affect the performance of WPT systems. One of the critical parameters in the wireless power transfer system is the coupling factor that relies on the primary and the secondary coils and the mutual inductance between these coils. Therefore, coupling factor estimation is a challenging issue in wireless power transfer. Many papers concentrate on this issue and explain ways to estimate the coupling factor between the primary and the secondary sides. Using the primary and secondary currents is conventional methods to estimate the coupling factor, but these methods have significant disadvantages. These methods must have many system parameters, complicating the control system. In this paper, a new method of coupling factor estimating addresses this problem in a wireless power transfer system with series-series topology. In this method, a modified 3<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> harmonic current is used for impedance and coupling factor estimation. While the conventional methods need all the system parameters, this method requires the primary inductance and input impedance, the inverter output voltage, and the primary current. It reduces the complexity of the control system and coupling factor estimation error. The viability of a proposed method is verified with an experimental prototype.