The Research On Islanding Detection And Protection Methods For Distributed Generation System

In recent years, distributed generation has developed rapidly, and its permeability in power system has increased year by year. In many research problems of distributed generation, the problem of isolated island is one of the focuses of people’s attention. Island may cause certain harm on the system, distributed generators, power equipment, and maintenance personnel. Thus island detection and protection is very important. It is the core of the island problem. The paper based on the distributed grid-connected interface device, to achieve protection, monitoring, anti-islanding, electric quality monitoring and communication protocol and so on, to achieve a large number of distributed power grid connected solutions finally. The paper analysis and research distributed generation grid connected system islanding detection technology in-depth.The main research contents in this article are as follows:(1) The paper analyzed the principle of the island detection, introduced the common detection methods, and analyzed their advantages and disadvantages. Through comprised and analyzed several common detection methods, it can be found that there were some imperfections in all kinds of detection methods. A new type of low voltage anti-island protection strategy was proposed, which can detect the dead zone of the isolated island in the case of the output power of the inverter and the load power balance. The new strategy used low voltage anti-island device, by discriminating the adaptive variable load to apply the anti-island system, which can destroy the condition of distributed generation island balance operation, and realize the function of anti-island.(2) The paper presented a detailed scheme of the large number of distributed power grid connected based on the distributed grid-connected interface device. Scheme was introduced in detail from two aspects:the main protection and the communication management. The distributed grid-connected interface device not only integrates the protection, monitoring, anti-islanding, electric quality monitoring function, but also has a protocol conversion, remote control and information encryption function. It has strong ability of integration and expansion of capacity.(3) Based on a new distributed grid-connected interface device and low voltage anti-island device, the paper proposed the overall framework of the anti-island system. The system discriminated the adaptive variable load to apply into it, changed the characteristics of the overall load, so that the passive island detection has no dead zone. The system can solve the problem of fast off grid after isolated island operation, and lay a solid foundation for the large number of distributed power grid connected supply.(4) Finally, the paper built a PSCAD simulation platform of a photovoltaic power generation. Experiments of connected with the grid system and isolated island detection were carried out. The process of anti-island protection by adaptive variable load was simulated, and the experimental results were analyzed.