Fault Analysis And Calculation Of Asymmetric Operation In Distribution Netwok Based On Symmetrical Component Method

The distribution network plays a role in the power system.It receives power from the transmission network and distributes it directly to industrial and civilian power users after the step-down conversion.The reliability of the distribution network directly affects the reliability of the user's power supply.The power supply efficiency of the distribution network directly affects the economics of the power grid.The structural rationality of the distribution network also directly affects the quality of the power provided to the user.Relevant statistical results show that most of the current unplanned power outages are related to the faults of the distribution network,so it is necessary to do a good job of fault diagnosis of the distribution network to improve the quality of the power gridThe phase component method and the symmetrical component method are two commonly used methods in dealing with the problem of asymmetric operation of power systems.Because the phase component method is directly calculated and analyzed under phase coordinates,it can intuitively reflect the actual situation of the power system,but its model is complex in application,the steps are cumbersome,the calculation amount is large,and the space occupied is large,so that the phase component method The use of this has been subject to certain constraints.The symmetrical component method can decompose the three-phase asymmetry into the positive sequence,negative sequence,zero sequence three-phase symmetric three-order component,and the three-sequence component has independence,which makes the fault calculation intuitive and concise,and its physical model is simple,and the calculation The amount is small and the calculation speed is fast.However,the symmetrical component method can only deal with power system faults with symmetric three-phase parameters.When the three-phase parameters are asymmetrical,the method will no longer be applicable.In China's distribution network,there are widespread problems related to the asymmetry of the power supply link and the asymmetry of the three-phase load.In the process of dealing with this problem,the traditional symmetrical component method cannot be effectively decomposed,which can not meet the application requirementsTherefore,in order to make full use of the advantages of the symmetrical component method to analyze and calculate power system faults,in the face of the three-phase parameter asymmetry and load asymmetry of power system lines,this thesis proposes a method for network structure equivalent transformation.The method transforms the asymmetric part of the three-phase parameters in the power network into a symmetric three-phase parameter network structure with certain "faults",so that it satisfies the preconditions for the use of the symmetrical component method.When the part of the original three-phase parameter asymmetry fails,it can be regarded as a complicated fault in the symmetrical part of the three-phase parameter after the equivalent transformation.For the complex fault of the power system,the symmetrical component method can be combined with the port network theory for analysis and calculation.The method can apply the symmetrical component method in the three-phase parameter asymmetry system,which can effectively reduce the calculation amount and simplify the analysis process.The accuracy and feasibility of the proposed algorithm are verified by analyzing and comparing the results calculated by the algorithm and the simulation results of the corresponding simulation platform.