Research On Fault Diagnosis Method Of Distribution Network With Distributed Power Supply Based On Petri Net

As the terminal of the distribution system,the low-voltage distribution network has the characteristics of changeable operation mode,complex line structure and many branches,so there are more and more factors affecting its safe and stable operation.A fast and accurate fault diagnosis method for low-voltage distribution network can play an important role in improving the reliability and stability of the system.Most of the existing fault diagnosis methods are based on transmission network and traditional distribution network,and are not suitable for low-voltage distribution network fault diagnosis under the condition of large number of distributed generations.This paper theoretically analyses the characteristics of the fault state after the distributed generation is connected to the distribution network from the aspects of voltage and line protection.According to the direct grounding mode of neutral point in the low voltage distribution network,the phase difference of the current flowing through the fault section through Clark transformation is selected as the judgment basis of whether the fault occurs in the section.The fault information based on FTU(Feeder Terminal Unit)is proposed.Fuzzy Petri nets modeling method,probability information measure can select the solution of the highest reliability in uncertain events,and verify the strict applicability of the fuzzy Petri nets to the fault section of distribution network.A double-layer fault diagnosis criterion for low-voltage distribution network without distributed power supply is proposed,and the first one is the fault current direction criterion.The second layer is Clark current phase angle difference criterion.With the probability information measure of the fuzzy theory,it can locate the fault section accurately and improve the fault tolerance in the case of information distortion or loss at the feeder terminal.The fault diagnosis rules based on FTU current information are introduced.According to the fault criterion and system structure,the general Petri net models of open-loop distribution network without distributed generation and low-voltage distribution network with distributed generation are constructed respectively.For complex distribution system,the fault section can be located quickly and accurately by combining the general model.The effectiveness and feasibility of this method are verified by simulation of an example system.