A Study on Anti-Islanding Detection Algorithms for Grid-Tied Photovoltaic Systems

This work presents a Matlab/Simulink study on anti-islanding detection algorithms for a 100kW Grid-Connected Photovoltaic (PV) Array. The main focus is on the islanding phenomenon that occurs at the Point of Common Coupling (PCC) between Grid-Connected PV System and the rest of the electric power system (EPS) during various grid fault conditions. The Grid-Connected PV System is simulated under the conditions of islanding, and anti-islanding (AI) relay reaction times are measured through the simulation. Results are presented for Grid-Connected PV System equipped with various AI prevention schemes such as over-current and under-current (OI/UI), over-voltage and under-voltage (OV/UV), over-frequency and under-frequency (OF/UF), rate of change of frequency (ROCOF) and Vector Shift. These scenarios are used to evaluate and determine the performance of the AI detection methods and select the most appropriate AI detection algorithm and its corresponding settings for Grid-Connected PV Systems. The AI protections was tested in case of complete disconnection of the PV system from the electric power grid and also in case of various grid faults. However, the detailed simulation results are presented only for the first study case. The theoretical simulation results are useful to design the AI protection devices for Grid-Connected PV Systems and select the points where islanding conditions may occur and the AI relays should to be inserted. From the results provided by the performed Matlab and Simulink simulations, it was observed that using traditional relays for islanding detection such as the OI or UV resulted in significantly better performance in respect to detection time of islanding conditions. The ROCOF and Vector Shift relays have a detection time comparable with frequency relays. However, if the ROCOF threshold is exceeded, the formation of an island is quickly detected. The effects of unintentional islanding were observed from simulation of transient grid faults on a power distribution network. The protection equipment needs to distinguish between islanding event and grid faults. The Grid-Connected PV System Anti-Islanding Protections should detect the fault and trip before islanding occurs as a result of the opening of the circuit breaker in response to a downstream fault.Please cite my paper in your work: I. V. Banu, M. Istrate, D. Machidon and R. Pantelimon, "A study on anti-islanding detection algorithms for grid-tied photovoltaic systems," 2014 International Conference on Optimization of Electrical and Electronic Equipment (OPTIM), Bran, 2014, pp. 655-660. doi: 10.1109/OPTIM.2014.6850940 URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6850940&isnumber=6850869本研究针对100kW并网光伏（Grid-Connected Photovoltaic, PV）阵列的孤岛检测算法开展Matlab/Simulink仿真研究。研究核心聚焦于并网光伏系统与电力系统（Electric Power System, EPS）公共连接点（Point of Common Coupling, PCC）在各类电网故障工况下产生的孤岛现象。本研究在孤岛工况下对并网光伏系统进行仿真，并通过仿真测量防孤岛（Anti-islanding, AI）继电器的动作响应时间。 针对搭载过流/欠流（Over-current and Under-current, OI/UI）、过压/欠压（Over-voltage and Under-voltage, OV/UV）、过频/欠频（Over-frequency and Under-frequency, OF/UF）、频率变化率（Rate of Change of Frequency, ROCOF）以及向量偏移（Vector Shift）等各类防孤岛防护方案的并网光伏系统，本研究给出了对应的仿真结果。上述仿真场景用于评估各类防孤岛检测方法的性能，筛选出适用于并网光伏系统的最优防孤岛检测算法及其对应参数设置。 本研究分别测试了光伏系统与电网完全断开的工况，以及各类电网故障工况下的防孤岛保护性能，但仅针对首个研究案例给出详细仿真结果。本研究得到的理论仿真结果可用于设计并网光伏系统的防孤岛保护装置，确定孤岛工况的发生位置以及防孤岛继电器的安装点位。 通过本次Matlab与Simulink仿真得到的结果可知，采用过流或欠压这类传统继电器进行孤岛检测，在孤岛工况检测时长方面表现更优。频率变化率与向量偏移继电器的检测时长与频率类继电器相当，但当频率变化率阈值被突破时，可快速检测到孤岛的形成。通过对配电网络暂态电网故障的仿真，可观测到非计划性孤岛的影响。保护装置需要区分孤岛事件与电网故障。并网光伏系统防孤岛保护应在因下游故障触发断路器跳闸而引发孤岛前，完成故障检测并执行跳闸动作。 若在工作中引用本研究内容，请标注以下文献：I. V. Banu, M. Istrate, D. Machidon 与 R. Pantelimon, "A study on anti-islanding detection algorithms for grid-tied photovoltaic systems", 2014年国际电气与电子设备优化会议（OPTIM）, Bran, 2014, pp. 655-660. DOI: 10.1109/OPTIM.2014.6850940，链接：http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6850940&isnumber=6850869