Development Of Fault Simulation Software For Distribution Network With Distributed Generation

Distribution network is an important part for power system distributing electric energy to terminal users.Currently,the increasing connection of distributed generations to distribution network has brought many significant changes to the structure of traditional distribution network.Therefore,modelling analysis of distributed generations and performing accurate fault transient calculation for distribution network can provide an important data source for protection device,testing system and safety assessment of distribution network.And it has important guiding significance for the planning,designing and operating of distribution network.A large amount of fault data is required in the theoretical analysis or study of fault transient,we can obtain the failure data by conducting dynamic simulation test or performing simulation calculation.The dynamic simulation test is difficult to carry out and it requires high cost and testing conditions,so its large-scale application is restricted.While the mainstream simulation software such as PSCAD/EMTDC,ATP-EMTP belong to commercial software,the calculation model of various elements has been solidified in the program,this can not meet the needs of self-development.Therefore,based on Canadian professor H.W.Dommel's discrete calculation theory of electromagnetic transient,this paper established the discrete mathematical model of the main components in distribution network,such as power supply,circuit breaker,transformer,transmission line,fault module,etc.What's more,the discrete mathematical model of the typical distributed generations is studied and analyzed,and also obtained the equivalent simplified model for fault transient calculation.Thus the fault transient calculation program is developed,including the admittance matrix subroutine,the matrix triangular decomposition subroutine,the line phase-model transformation subroutine,the transformer calculation subroutine,etc.And the graphical user interface is also designed.This simulation software can graphically build simulation model of distribution network with distributed generations and easily input simulation parameters.It can also perform various of fault state transient calculation for distribution network by setting a variety of operating nodes and fault scenarios.Thus,it generates the node voltage and branch current before and after the fault,in order to provide the data source for theoretical analysis,protection device or test system for distribution network.Finally,using a simulation model of the typical distribution network with distributed generations simulates different fault types,such as single phase grounding fault,double phase-to-earth fault,double phase short circuit and three phase short circuit.Compared with the results of PSCAD/EMTDC,it shows that the fault transient calculation program has a high precision and it can better meet the needs of diversified fault data for relay protection or testing system of distribution network.