The Research Of Islanding Detection In Single-Phase PV Grid-Connected System

PV Grid-connected power generation is an important form for distributed generation. One of its key technologies-Islanding detection technology become a high-profile topic at present. Islanding effect is a fundamental problem of PV grid-connected system, PV grid-connected system is likely to remain when power is lost because of the failure or maintenance. Which threatens the security of grid maintenance personnel, cause damage to electrical equipment and so on. Therefore, islanding detection of grid-connected device must have a protective function.This paper is the research of islanding detection in single-phase PV grid-connected generation system, the main research contents are as follows:1, Research background of the topic is introduced briefly, that is, increasing shortage of conventional energy, and growing of emerging energy research. Then introduced the basic issues of islanding detection, mainly including the formation and harm of islanding, detection method research status, and domestic and international testing standards.2, Inverter-resident detection method is expounded. For passive and active islanding detection methods, their principles and advantages and disadvantages are analyzed emphatically.3, The issue of single-phase grid synchronization-phase-locked loop (PLL) technology is discussed. This paper analyzed small signal model of PLL, introduced some classic method about adapted filtering technology, and also analyzed the PLL based on the second-order generalized integrator (SOGI-PLL).The SOGI-PLL can void common second harmonic produced by PD, and greatly reduce the disturbance of grid and the influence of harmonic, easily design and achieved. Then the method is verified by simulation and experimental. Finally, a new frequency-locked loop (FLL) is analyzed. FLL is a non-linear system, this paper presents a practical design method for FLL4, A detailed analysis is done in this paper on islanding detection method based on the PLL. Non Detection Zone (NDZ) of this method is discussed for two cases (purely resistive and parallel RLC load) to determine success of islanding detection thresholds. The simulation and experiment verify the feasibility of this method.