Mutual Inductance and Load Estimation in Wireless Charging Systems via Port-Impedance Analysis

Load and mutual inductance are critical parameters for ensuring optimal matching in wireless power transfer (WPT) systems. The precise identification of these parameters is fundamental for ensuring interoperability between diverse charging devices. This paper presents an online method for identifying both mutual inductance and load parameters, utilizing the port impedance of the transmitting coil in an LCC-compensated WPT system. Initially, an analysis of the WPT system's network characteristics is conducted, deriving the relationship between port impedance, load, and mutual inductance. The load and mutual inductance identification processes are then decoupled. By introducing a fictitious ratio, the complex load identification equation is simplified into a quadratic form, enabling the inverse determination of mutual inductance from the identified load. A simulation model is created at the end to verify the proposed approach. The results reveal that, under different coupling and load scenarios, the maximum errors in identifying the load and mutual inductance are 6.8% and 4.8%, respectively. Importantly, the proposed method does not depend on resonance approximations or real-time communication, showcasing its practicality and robustness for wireless charging systems.