This article investigates the use of Impedance Spectroscopy (IS) to identify mismatches in Photovoltaic (PV) panels/string/array, particularly for detecting partial shading effects. The findings confirm IS as a promising tool for on-field applications, especially in small-scale urban power plants where partial shading is a common issue. An analysis of several experimental impedance spectra measured with PV panels operating at their Maximum Power Point (MPP), with controlled partial shading conditions, reveals that partial shading induces a characteristic double-arc deformation. This feature could be leveraged in a diagnostic tool for mismatch detection. The key advantage of this approach is its ability to perform IS measurements at MPP, preserving the normal operating conditions of the PV panels/string/array. Additionally, IS requires minimal modifications to the system's architecture and integrates easily into existing power electronics interfaces. To validate the consistency of impedance spectra under partial shading, experimental data were compared with two models: a Constant Phase Element (CPE) model adapted for PV strings in non-uniform conditions and an enhanced Single-Diode Model (SDM) developed for SPICE3-based simulations. The results confirm that IS successfully adjusts the models and detects mismatches in both experimental and simulated scenarios, demonstrating its scalability and effectiveness as a state-of-the-art PV diagnostic tool.

Impedance Spectroscopy (IS) is widely used to analyze the dynamic behavior and degradation of electrochemical systems such as batteries. IS has also been successfully applied to study the performance and degradation mechanisms of photovoltaic (PV) devices. Traditionally, IS is performed with Frequency Response Analyzers (FRA), which apply small-signal perturbations and measure the impedance response of the system. However, those instruments are costly and not suitable for in situ diagnostics. This work proposes a methodology to perform IS measurements on PV systems using a power converter, thereby eliminating the need for external specialized equipment. The proposed approach includes a theoretical analysis of the converter dynamics to derive an expression for the duty cycle amplitude, which is required to maintain a constant perturbation magnitude across a range of frequencies. The methodology is experimentally validated using a synchronous Boost converter connected to a PV panel and controlled by a Texas Instruments F28379D digital signal processor (DSP), which injects the perturbation signal in the converter’s duty cycle. Moreover, the voltage and current measurements are performed with an oscilloscope. The results demonstrate that the proposed converter-based IS method accurately reproduces the impedance spectra obtained with a commercial FRA, confirming its feasibility as a low-cost, flexible, and scalable solution for PV impedance characterization and diagnostics.