Online Impedance Spectroscopy Characterization of PV Panels by Studying Resonant Behavior of Boost Converter

Impedance spectroscopy (IS) is a powerful in-operando characterization tool in the electrochemical domain which allows acquiring system internal impedances over a wide frequency range. Such information is valuable for understanding of the fundamental processes occurring within the system at different timescales. Compared with the specially designed work-stations for IS implementation, the converter based IS is more advantageous in reducing the system cost and facilitating onboard applications, as no additional device is required. Considering the control simplicity and tracking rapidity, the open-loop control scheme for online IS implementation is initially studied and analyzed in this work. Due to the series connection of the inductor and the capacitor in the conventional boost converter, resonance can occur as the resonant frequency is usually covered by the wideband perturbation frequency. The resonance can cause the operating points to enter the nonlinear operating region of the target system and lead to invalid and distorted IS measurements. In this work, aiming at the photovoltaic (PV) panels, the influences of different system parameters, including parasitic resistances, converter passive components and steady-state output power, on the resonant behavior in open-loop control are systematically analyzed. Both simulation and experimental results are given to verify the proposed design guide.