Modeling And Fault Characteristic Simulation Of Active Distribution Networks Based On Rtds

With the extensive application of distributed generations(DG),the active distribution networks(ADN)are becoming more and more common.The structure of the active distribution network is more complicated and its fault characteristics change greatly.Especially,the fault characteristics of the inverter-based distributed generation(IBDG)are significantly different from that of traditional source.In order to develop new protection device suitable for ADN,it’s necessary to make comprehensive and accurate fault characteristics analysis of ADN.Therefore,based on the Real-Time Digital Simulator(RTDS),this paper carry out research around the modeling and fault simulation of ADN.The main work of thesis are as follows.The systematical simulation model of ADN is established based on RTDS.Firstly,the simulation model of photovoltaic generation is built,including the primary equipment and the control system.Then,based on the typical distribution network with radial structure,the systematical simulation model of ADN is established,including 2 IBDGs under PQ control.The fault simulation and fault characteristics analysis of the ADN are conducted.Based on the simulation model of ADN,the comprehensive simulation under different fault situation is performed,and the influence of fault type,fault location and transition resistance is analyzed.Phasor and sequence component calculation is conducted using simulation data,and then the magnitude and distribution characteristic of voltage and current phasor and their sequence component in ADN is directly anlyzed.Simulation results demonstrate that the integration of IBDG makes the fault characteristics of ADN and traditional distribution networks different significantly.Transition resistance can affect the voltage sag at point of common coupling and the angel of positive current on the ends of fault points.Analytica calculation for fault conditions in ADN is performed and the analysis verifies the correctness of simulation results.Taking into account the influence of the control strategy,the voltage-controlled current source is used as the fault equivalent model of IBDG and the fault current calculation method is provided.The fault equivalent circuit of ADN containing IBDG is established under different fault conditions.Voltage and current equations are established by the mesh current method,which are solved by the iteration method.The theoretical calculation results verify the correctness of the simulation results.A close-loop test platform for ADN equipment is constructed based on the ADN simulation model.On the basis of ADN model,the structure of the close-loop test platform is designed,and the usage of RTDS’s related board and the overall control logic are introduced.Then,a close-loop test for a protection device is carried out on the platform,which verifies the feasibility of the test scheme.