Research on lightning transient field-line coupling and systematic protection for ultra-large-scale photovoltaic systems

Abstract

With the rapid development of renewable energy, ultra-large-scale photovoltaic (PV) systems face three major challenges in lightning protection. First, existing electromagnetic transient simulation tools lack sufficient accuracy when modeling ultra-large-scale systems due to neglected high-frequency electromagnetic coupling effects and the "curse of dimensionality." Second, conventional lightning protection standards fail to address the unique hybrid AC/DC configurations and wide-area distribution of PV systems. Third, the absence of scientific risk assessment methods leads to unquantified operational decisions. To address these challenges, this study establishes a field-line coupling model for lightning electromagnetic transients and develops a systematic protection framework. Through theoretical and technological innovations, the following key achievements were made: 1. Modeling Methodology: A novel PEEC-FDTD hybrid algorithm enables accurate simulation of PV systems by combining circuit parameter extraction with time-domain electromagnetic field solving. A potential-line coupling model improves convergence while a dynamic charge-wave lightning channel model enhances near-field precision. 2. Protection Optimization: An innovative topology replaces conventional large-loop cable designs with small intersecting loops, significantly reducing induced voltages across bypass diodes. Grounding system optimization demonstrates that distributed electrodes and interconnected schemes lower overvoltages during direct strikes. 3. Standardization: Comprehensive grounding experiments quantify transient impedance effects, revealing performance differences between conventional and segmented designs. Dual-end cable armor grounding limits core-sheath voltages below safe thresholds. 4. Risk Assessment: A partition-based heuristic algorithm implements symmetry-driven quadrant reduction and risk-adaptive zoning, achieving accelerated computational efficiency while maintaining accuracy. The methodology balances protection requirements and cost-effectiveness through voltage threshold optimization. By integrating field-line coupling modeling with systematic protection technologies, this study resolves key challenges in simulation accuracy, standard adaptability, and economic evaluation for ultra-large-scale PV lightning protection. The results provide actionable solutions for safe operation under complex meteorological conditions.