Protection Technology Of DC Distribution System

With the development of society and economy, the electric power system has changed significantly in terms of the forms of power generation and consumption. The traditional AC power distribution system is facing challenges such as insufficient capacity and limitation of line corridor. At the same time, with the progress of power electronic technology, the DC distribution system has showed the huge technological and economic advantages in transmission capacity, reliability of power supply, transmission efficiency and other aspects. However, the secure and stable operation of DC distribution system is influenced by the operating performance of its protection system. Therefore, this thesis is focusing on the protection technology of DC distribution system.Firstly, this thesis analyzes the construction principles of the DC distribution system in terms of selection of the voltage grade, topological structure and grounding mode. The mathematical model and control strategy of a typical DC distribution system is then established and simulated in Matlab.Secondly, in order to facilitate fault analysis, the DC distribution system has been divided into different fault zones according to fault position. Then the characteristic and impact of various types of faults within respective fault zone is analyzed. The process and characteristics of DC-side short circuit fault is mainly studied through theoretical analysis and simulation analysis. The fault characteristic of DC distribution system is summarized on the basis of the above analysis.Thirdly, the application of the fuse, disconnector, DC circuit breaker and other common DC protection devices in DC distribution system is investigated and discussed. Then the technical difficulties of DC circuit breaker and the advantages and disadvantages of different types are analyzed. A new hybrid DC circuit breaker topology is proposed which can turn off rapidly and is verified by Matlab simulation.Finally, the requirements and the difficulties of DC distribution protection system are analyzed and different protection zones are established. Focused on the application of current differential protection in the DC bus and line protection, the protection principles and technical difficulties are studied and analyzed by Matlab simulation.