分布式发电的孤岛检测方法研究-电力系统及其自动化专业论文.docxVIP

华 华 中 科 技 大 学 硕 士 学 位 论 文 II II Abstract The extensive use of new energy and the instability of existing large power grid, have made distributed generation(DG) getting more and more popular in the power system. And the applications of DG have brought many advantages to the power grid, for instance improving the quality of the electricity, minimizing peak loads and helping achieve optimal allocation of the resource. However, the parallel operating of DG with main grid has brought vast problems, one of which is islanding. When power supply from main grid is interrupted(for example the power failure of the main grid),these independent parallel distributed systems will still continue working, and keep independent operating connected to the local loads, so this operating status of DG can be told as islanding. That is, when main grid trips due to certain reason, every user client of parallel distributed systems cannot detect power failure in time and excises itself from main grid, so it will form an independent power supply islanding containing DG and local loads. The islanding operating of parallel distributed systems is likely to do harm to main grid, electrical equipments and maintenance personnel, so it is needed to take measures to monitor the operating status of parallel distributed systems after islanding, and excises itself from main grid after islanding is detected. This article will research islanding and traditional islanding detection methods, and put forward a new islanding detection method according to their characteristics. This article firstly introduces the concept of DG and the development situations, and then briefly explains the reasons of islanding and a series of damages it brings, and details the theory of existing detection methods and its advantages and disadvantages. We emphasize two methods: ROCOF and VS, and propose a new detection method based on frequency detection after comparing traditional detection methods. At the same time, this article