Analysis Of Islanding Detection For Inverter-based DG On-grid Systems

Distributed generation systems (DGS) as a supplementary energy source of theconversional centralized generation system, are playing an important role. For the DGStechnologies, Islanding detection is essential in order to meet the grid reliabilityrequirements. Thus each on-grid inverter is obligated to integrate anti-islanding detectionfunction according to the IEEE Standards. This thesis is focus on the grid-connected PVsystems, and the main achievements of this work are as follows:the dual-loop control system of the inverter with voltage outer loop and currentinner loop is designed to integrate the island detection algorithm, in addition with thefilter capacitor current feedback equivalent as an increased damping resistance, to solvethe resonant peak problem caused by the third-order characteristic of the LCL filter;various conversional active islanding detection methods are analyzed and compared byevaluating the Non-Detection Zone (NDZ) of each, and the physical explanationcorrelated with the load intrinsic characters is also proposed; the novel concept ofverifying detection effects in the whole load condition instead of any single one whichwould be more applausive to make a performance conclusion is brought out; and finallyan improved anti-islanding detection method based on the active power NDZ evaluationthat combined the benefits of the passive Over/Under Voltage Protection (O/UVP)method and the Active Frequency Drift (AFD) method is presented to obtain a betterperformance of system output power increase, the simulation results are shown to verifythe effectiveness of this method.