Bifurcation-Based Parameter Extraction Method for IPT Systems with Sensorless Metal Object Detection

This paper presents a novel bifurcation-based parameter extraction (BBPE) method for inductive power transfer (IPT) systems. The proposed method utilizes only transmitter-side measurements to accurately determine all coil parameters, including the complex coupling coefficient, making it useful for both optimizing power transfer and efficiency, as well as sensorless metal object (MO) detection. The method is based on two primary current frequency responses, one measurement with an open load and the other with a shorted load. The primary current amplitude spectrum for an open load contains one peak, while a shorted load puts the system in a deep bifurcation state, resulting in two peaks and one minimum. The resonant frequencies and primary current amplitudes at the peaks for the two loads are measured and used to solve for the coil parameters. With its ability to extract all coil parameters, this method is an improvement over previous techniques that could only extract a subset of parameters using transmitter-side information. Measurements of an IPT system with and without an MO are used to validate the effectiveness of the BBPE method.