Research On Fault Diagnosis Of Micro-grid Based On Petri Net

With the development of national economy, higher requirements of the reliability and stability of power supply for power users has been put forward. The security and stability, reliability of power system is an important foundation of maintaining social production and daily life, which is also a major basis of promoting social development and progress. However, with the increase of the scale of power system, the problem of the large scale power system is becoming more and more serious. On the other hand, considered the shortage of fossil and the environment problem, coal and oil, natural gas for energy generation have seriously restricted the sustainable development of society. In order to achieve sustainable energy development and make full use of new energy, the concept of Distributed Generation and Micro-grid is proposed. Micro-grid provides power to local loads economically and environmentally, using distribution generation technology, which also reduces the adverse effects of the bulk power system.Reliability and continuity of power supply is required more and more highly, but the fault in power system is inevitable. It is necessary to monitor and eliminate fault quickly not to only ensure security and stability but also to enhance power reliability and continuity in Micro-grid. A high-quality fault diagnosis system is needed to realize the fault location and restore power supply quickly in Micro-grid. At present, domestic and foreign scholars mainly research on"expert systems","artificial neural network","fuzzy theory","genetic algorithm"and"Petri net"for fault diagnosis in bulk power system. However, the methods used in bulk system do not apply to Micro-grid, the topology of which is flexible and diverse.The paper has studied on the knowledge of Petri nets in depth and analyzed the fault diagnosis model based Petri nets in bulk system. Firstly, the paper analyzed the existed fault diagnosis model based on simple Petri nets. As the simulation of the simple Petri nets is not strong, the model based on Petri nets has a strong dependence on the structure of the grid. Therefore, it is fit for Micro-grid, which could work in flexible operation mode. Secondly, according to the development of high level Petri nets theory, the paper has analyzed the fault diagnosis model based on colored Petri nets. The reasoning process has been analyzed in typical Micro-grid topology. The shorts of the fault diagnosis based on colored Petri nets have been summarized according to the sample.Furthermore, the paper has analyzed the characteristics of Micro-grid and described the typical form of Micro-grid. Considering the requirements of protection and fault diagnosis in Micro-grid, combined with object-oriented thinking and database theory, the paper puts forward fault diagnosis model of Micro-grid based on high-level Petri net. The model also adds time stamps to the elements to achieve the priority of diagnostic logic. Taking into account that the protection fail to operate and the loss may happen in information transmissions, fuzzy theory is introduced in fault diagnosis model to enhance the robustness of the fault diagnosis model. Building a model based on protection action information to achieve the rapid internal fault monitoring and location in Micro-grid.