Indirect Lightning Strike Analysis of Blocking Diodes in a Large-Scale Photovoltaic System

This study investigates the vulnerability of blocking diodes in large-scale photovoltaic (PV) systems under indirect lightning strikes through advanced electromagnetic transient modeling. Focusing on a 15-array PV power plant in Yangjiang, Guangdong, a high-fidelity simulation framework was developed using the Partial Element Equivalent Circuit (PEEC) method to model interconnected PV arrays, grounding networks, and power conversion components. The analysis quantifies how lightning strike distance and current waveform steepness govern overvoltage dynamics in blocking diodes, critical components for preventing reverse currents. Results demonstrate a 79.5% reduction in peak overvoltage at diode terminals as lightning distance increases from 0.5 km to 2 km, with a critical safety threshold identified at 1.7 km where voltages exceed the 2 kV damage limit. Waveform analysis reveals that steeper lightning currents (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1 / 50 \mu$</tex> s front time) induce 58% higher initial voltage oscillations compared to slower waveforms (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10 / 350 \mu ~\mathrm{s}$</tex>), emphasizing waveform characteristics as key risk factors. Spatial vulnerability patterns show diodes farthest from the inverter (e.g., diode 15) sustain <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{2. 2} \times$</tex> higher overvoltages than proximal counterparts (e.g., diode 1) due to cumulative electromagnetic coupling effects. These findings, validated through multi-scenario simulations with 10 kA lightning currents and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.01 ~\mathrm{S} / \mathrm{m}$</tex> soil conductivity, provide critical insights for optimizing lightning protection systems in utility-scale PV installations, particularly regarding component placement, surge suppression strategies, and waveform-specific risk mitigation. The developed PEEC-based methodology establishes a robust framework for assessing electromagnetic transient threats in renewable energy infrastructure.