Phase-Identification-Based Mutual Inductance Estimation Methodology for Modular Wireless Power Transfer Systems

To achieve independent or refined control of modular wireless power transfer (MWPT) systems, precise mutual inductances are crucial. However, in MWPT systems, the number of mutual inductances grows factorially with the increase in the number of modules, making traditional single-channel mutual inductance calculation methods computationally complex and inefficient in practical applications. To address these challenges, this article introduces an offline mutual inductance estimation methodology for MWPT systems with a series-series (SS) compensation topology. By utilizing blocking or bypass switches in each module, measurement topologies capable of calculating multiple mutual inductances efficiently are constructed. To obtain sufficient equations, multiple measurements at different operating frequencies are performed. This approach effectively mitigates the estimation inaccuracy stemming from the tolerances of resonant components by considering the resonant frequency as a variable to be solved. Furthermore, due to the challenges and potential significant errors associated with phase angle measurement under high-frequency operating conditions, a phase identification method is introduced so that the proposed methodology only relies on measuring amplitudes of winding currents and voltages. Moreover, a quantitative analysis of the factors that may cause errors in the estimation is provided. Finally, two-module and four-module WPT prototypes are constructed to validate the proposed method.