Research Of Fault Analysis And Protection For DC Distribution System

The DC distribution system is fit for the access of distributed generators(DGs) and DC loads, with the characteristics of high power quality, high transmission capacity and low economic cost. It can promote the development of DC appliances and DC ecological house, so it is the new direction of development in distribution area.This paper introduced the research background, status and development trend of protection and control technology in DC distribution system, explored some issues in DC distribution system protection and control. In the DC distribution system, power electronic device is a key part, connecting the different kinds of generators, transmission line and loads. At first, this paper explores and gives a DC distribution system equipment selection principle to meet the need for actual DC distribution system project. Secondly, the power electronic device determines the fault characteristics. Scientific fault analysis is the basis for the development of power system relay protection technology, and the research focus on fault analysis in this paper is DC short circuit fault, which is the most serious fault in DC distribution system. According to different work modes of power electronic devices and fault locations, this paper divided the fault transient process into 4 phases, carried out rigorous theoretical analysis on DC short circuit by establishing an equivalent circuit. At last, based on the fault characteristic, this paper proposed the DC line fast protection and segmented current protection for DC distribution system.Based on electromagnetic simulation software PSCAD / EMTDC, a DC distribution system model is built. By simulating the short circuit fault at different locations, the versatility of the fault analysis method is verified. Using Matlab to analyze the simulation data, the speed and reliability of two proposed protection principles are verified.