A dq-Axis-Based Current Perturbation Control Method for Real-Time EIS in Fuel Cell DC-DC Converters

Fuel cells are increasingly regarded as a core power source in future energy systems owing to their high efficiency and low emissions, driving demand for real-time diagnostic technologies. Electrochemical impedance spectroscopy (EIS) is an effective method for quantitatively characterizing degradation and performance loss in fuel cells. Recent efforts focus on implementing real-time EIS using DC – DC converters. However conventional PI-based current control suffers from limited bandwidth, resulting in phase lag and magnitude attenuation at high perturbation frequencies, which degrades the accuracy of impedance measurements. This study proposes a dq-axis-based current perturbation control method for EIS implementations in a fuel cell DC-DC converter. Perturbation currents are transformed into a synchronous rotating frame, regulated as DC components for accurate high-frequency tracking. A hybrid structure with PI control for low frequencies is employed. Simulations and experiments validate improved tracking up to several kHz, ensuring stable EIS operation.