大型光伏阵列的雷电瞬态研究

This project presents a novel method for evaluating the circuit parameters of frame branch, grounding electrode and combining network of large scale photovoltaic array. The circuit model is built for determining the potential and current distributions in the frame structure. The prediction is further made about the locations where high potential and current appear and back-flashover distance on the solar panel. The current-dividing and equipotential measures are also proposed for the frame structure. Based on the time-varying electromagnetic field theory, a numerical algorithm is proposed to calculate the transient electromagnetic filed in the spatial domain of the photovoltaic array, by which electric and magnetic fields can be obtained from the current distribution on the frame branches. The induced voltage and current can also be given in the loop of the combining network. From the heat source formed by the current paths, the heat conduction equation that describes the transient temperature rise process of solar panel is solved numerically. The harmful degree of the temperature rise is assessed for the solar panel. Subsequently, the equivalent circuit is constructed for the electric power transmission system of photovoltaic array. The software simulation is performed for investigating the coordination characteristic and overvoltage protective reliability of the multi-stage surge protective devices. The protective performance indexes are determined and the prototypes are developed for the surge protective devices. Then, the reduced-scale experimental arrangement is set up for the photovoltaic array. The measurements are taken for the potential, current, induced voltage and temperature and the factors that influence these quantities are experimentally enquired. The comparison is made between the measured and calculated results to examine the validity of the model and algorithm presented in this project.

本项目将推出大型光伏阵列框架分支、接地体和阵列汇流网的电路参数计算方法，建立阵列的电路模型，计算阵列中雷电流和瞬态电位的分布，预测大电流与高电位的出现部位和雷电反击距离，对阵列框架提出分流与电位均衡措施。从时变电磁场理论入手，给出阵列空间内雷电瞬态电磁场的数值算法，由框架分支雷电流分布计算阵列空间瞬态磁场和电场，确定阵列汇流网感应电压与电流。根据边框分支雷电流和回路感应电流，数值求解描述电池板瞬态温升过程的热传导方程，评估温升对电池板的危害程度。搭建光伏送电线路系统的仿真网络，仿真分析线路上分级电涌保护器之间的配合特性及其对过电压防护的可靠性，确定保护器指标，研制专用保护器的样机。然后制备光伏阵列的缩型试验模型，测取试验模型中的瞬态电流、电位、感应电压和温升，试验调查影响这些量的主要因素，并将试验测量结果与理论计算结果加以对比，以校验理论计算模型与算法的正确性。

本项目已按原定计划完成。通过开展项目研究工作，本项目提出大型光伏阵列中空间分支和接地体的电路参数计算方法和阵列的等值电路模型，建议简化的瞬态响应求解算法，计算阵列中雷电流和电位瞬态响应，调查影响这些瞬态响应的主要因素，确定阵列构架中大电流与高电位易于出现的部位。从阵列构架中的雷电流分布出发，计及构架分支导体中的集肤效应，求解分支导体的瞬态发热过程，预测分支导体的温升水平。根据时变电磁场理论，提出阵列空间内雷电瞬态磁场的数值算法，由构架中雷电流分布求解阵列空间瞬态磁场，获取集电汇流回路中感应电压。建立光伏送电线路系统的仿真网络，仿真分析线路上分级电涌保护器限压效果，并对现有的直流电涌保护器进行改进，研制新型的保护器样机。然后从反映实际光伏阵列中雷电流传输流动波特征的要求出发，制备快速冲击电流发生器和缩型阵列实验模型，系统测取实验模型中的瞬态电流、电位、温升和感应电压，并将实验测量结果与理论计算结果加以对比，以全面校验本项目所建立理论计算模型与算法。本项目推出的研究成果将能为大型光伏阵列的防雷设计提供有效的支持。