Research On Key Issue Of Relay Protection In The Micro-grid

With the development of society, energy problems increasingly attract the attention of people all in the world, how to make use of renewable energy sources efficiently and to maintain the sustainable development of human society has become the direction of the development of the power industry. The micro-grid fully coordinate the contradiction between power-grid and distributed power supply, and has achieved the goal of highly efficient utilization, as the main form of utilization of distributed energy, has been widespread concerned in our society.Micro-grid is an integrated unit containing controllable load, micro-power, energy storage devices and varieties of control systems, and makes full use of the advantages of distributed power and flexibility to meet the systems and security requirements. However, due to the different operating modes, the fault characteristics of micro-grid control mode will be different and the traditional protection solutions will not meet the requirements. Therefore, there will be great significance to study the relay protection of micro-grid.Firstly, this thesis summarizes the current research status of micro-grid and micro-grid protection at home and abroad and the protection method. We mainly summarize the protection method in three aspects:the fault characteristics, micro-power modeling and protection schemes. Secondly, the micro-grid structures, operation modes and micro-grid control strategies are introduced, and the paper focus on theoretical analysis of the fault characteristics at constant frequency with constant voltage and micro-power under constant power controlled. Secondly, the fault characteristics of micro-power were simulated using the matlab, a kind of simulation software. Finally, a micro-grid protection scheme based on the fault area searching is proposed, and an example is utilized to validate its protective properties to make a comment.At the end of this thesis, the paper sums up the main research work and points out the direction of future research.