Research On Dc Distribution Network Line Fault Protection And Location Method

With the rapid development of wind power,photovoltaic and other renewable and clean energy and the wide application of DC load,DC distribution network has become an important part of the future smart grid.Among them,high-performance DC protection scheme is an important guarantee for the safe operation of DC system.Considering the particularity of fault and protection of DC distribution network,this paper adopts the method of combining theoretical analysis and simulation verification to study the protection scheme and fault location method of DC distribution network.Firstly,the research background and significance of this topic are described,and the research status of protection principle and fault location in DC distribution network is summarized and analyzed.Secondly,the topological structure,voltage level,connection and grounding mode of DC distribution network are introduced.In this paper,the fault types of DC distribution network are classified,and the fault mechanisms of unipolar grounding and inter-polar short circuit are analyzed,which lays a theoretical foundation for the proposal of later protection and fault location scheme.Then,a longitudinal protection scheme based on the Pearson correlation coefficient of fault transient current is proposed.The relationship characteristics of the parallel capacitor current of the converter stations at both ends and the measured current at the line protection installation are analyzed after the fault of the DC distribution line,and the correlation between the two is characterized by the Pearson correlation coefficient.According to the difference of Pearson correlation coefficient under different faults,a protection scheme which can identify fault lines and fault types is established.Finally,a single terminal fault location method for DC distribution network based on distance measurement module input is proposed.The distance measuring module was put into the fault circuit to form RLC circuit.The characteristic parameters of capacitance voltage and discharge current of the distance measuring circuit were extracted by the least square method,and the equivalent impedance of the distance measuring circuit was identified.The relationship equation of fault distance,transition resistance and equivalent impedance was established to realize fault location.