Research on DG distribution network protection based on topological analysis and power automatic recovery scheme

摘要

It is needed to take islanding or micro grid as the power supply which can provide fault current when it concerns the fault diagnosis, on this premise, can the protection still maintain their its selectivity, because the micro grid or the intentional island will also serve as a power point to provide fault current for the fault point. How to select a set of protection algorithm, fully take the impact of the micro grid and the intentional island on the protection into account, and use the characteristics of the network internal power supply and load power balance so as to create useful conditions for fault diagnosis and removal? Based on the analysis of the network topology, the study takes the fault current at fault time (or the directional protection criterion in distribution network automation) as a search driver so as to lock the fault area and isolate the fau then the power load capacity is taken as the drive, by means of recursion layer by layer, namely, through the method of reverse search from root to leaf, the load is gradually loaded and polymerized, finally, the optimal power flow balance is found out so as to realize the best island division. This method is carried on by adopting different searches: at the fault time, each power supply is taken as the starting point, at the island division, the switching off of the power supply is taken as the starting point; with different search drives, at the fault time, it is driven by the fault current or the directional protection criterion, at the island division, it is driven by the power overload capacity; with different search directions, at the fault time, when the power supply directs to the power supply or load, it is positive, at the island division, when the switch directs to the power search, it is positive. In this way, it completes the protection control strategy which integrates the fault isolation with island division. Finally, the program simulation verifies the effectiveness of the algorithm.