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.

This work investigates an improved method for detecting and simulating the effect of partial shading on photovoltaic (PV) panels by combining experimental and simulation procedures. The method entails measuring current-voltage (IV) curves and impedance spectra for two Photovoltaic (PV) panels under outdoor conditions. The shade is then recreated in one panel, and measurements are repeated to generate a dataset for adjusting a Constant Phase Element (CPE). In addition, the single-diode model (SDM) is tested using the SPICE environment for further validation. Experiments are repeated at different irradiances and operation points to fully understand PV panel performance in diverse environments. The paper focuses on the experimental outcomes. This study examines tuning a CPE model based on experimental data and using the single-diode model in SPICE simulations. The study's comprehensiveness is demonstrated by presenting data for various irradiances and operating points. The improved CPE model's reliability and precision, as well as validation of the single diode model in SPICE, are emphasized. The findings from the experiments contribute to better comprehension of PV panel dynamics in non-uniform scenarios. The importance of reproducing these results in simulation for engineering applications is emphasized, providing the path for future advances in PV panel design and optimization based on spectrum measurements.

This article presents a method for characterizing the dynamic behavior of photovoltaic (PV) cells using the Electro-Impedance Spectroscopy (EIS) technique. High-precision laboratory equipment has been used to measure a single PV cell, capturing impedance (Z LB) and voltage-current (I - $V$ ) curve characteristics. We propose a model incorporating variable capacitance and conductance behavior for describing diode impedance dynamics. The experimental IV curve and impedance measurements are used as the reference for model parameters fitting through an evolutionary algorithm. Exploiting data from a single spectral measurement at a specific operating point, the methodology enables the prediction of the IV curve and spectral impedance plot at any operating point, as long as the irradiance conditions remain constant. The experimentation in a PV cell demonstrates a strong match between the obtained real data and the mathematical model. However, it is important to note that these findings are based on controlled simulated environmental conditions in a single cell. Further testing on PV panels is required to reproduce conditions such as mismatch or partial shadowing in order to stress and test the proposed model.

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.

Frequency-domain analysis is becoming common as a method for online Photovoltaic (PV) diagnostics. Traditional frequency-sweep methods are inherently slow. In contrast, faster analog multisine approaches require linear amplification hardware that is incompatible with the binary switching nature of standard power inverters. To address this compatibility, this manuscript proposes a solution based on Selective Harmonic Injection (SHI). The method synthesizes a deterministic Pulse Width Modulated (PWM) burst, embedding specific spectral content directly into the switching sequence. SHI allows for high-frequency characterization without increasing the converter's switching frequency. It permits standard power electronics hardware to perform wide-band diagnostics using pre-computed lookup tables preserving CPU cycles for essential control algorithms. By stimulating an Enhanced Single Diode Model (eSDM) with this pre-emphasized waveform, we evaluate both the transient behavior and the resulting impedance response. Validation against experimental measurements confirms that SHI effectively stimulates the slow PV dynamics without the need for external analog hardware. Gi Vref Vpv