Research On Protection And Fault Location Of Distribution Network With Distributed Generators

With China's modernization drive and development of new energy generation technology,it is an inevitable trend that the energy supply and demand structure transforms to clear and low-carbon.The Inverter Interfaced Distributed Generation(IIDG)is the main form of new energy generation at present.However,Distributed Generation(DG)not only has volatility and intermittence,but also participates in the regulation of voltage reactive power with the increase of its permeability,which leads to the change of fault characteristics of power grid and challenges the fault analysis and relay protection of power grid.Therefore,the following research work is carried out in this paper aiming at the protection of distribution network with IIDGs and the scheme of fault location.1.Based on the analysis of the output characteristics of PQ controlled IIDG,the equivalent fault model of IIDG with eliminating negative sequence current strategy and low voltage ride through(LVRT)is established.Considering the participation of IIDG in voltage reactive power control,the reference power estimation method of distribution network with multi-IIDGs based on the voltage and current information at both ends of the line in steady-state operation is proposed,which lays the foundation for the subsequent fault analysis.2.The fault equivalent circuit of distribution network with multi-IIDGs is established,and the fault voltage algorithm is proposed.Based on the reference power estimation method and fault equivalent model of IIDG aforementioned,the fault characteristics of the distribution network are analyzed,and the fault current algorithm is proposed.So as to construct the feeder current differential protection method of distribution network with IIDGs participating in voltage and reactive power regulation.Finally,a distribution network simulation model is built on PSCAD/EMTDC to verify the effectiveness of the proposed protection scheme.3.The fault additional network and zero sequence network of arc suppression coil grounding distribution network with IIDGs are established.The influence of IIDG accessing to distribution network on the location of single-phase grounding fault section is studied to reveal the mechanism that "IIDG affect the system transient process by changing the amplitude and phase of fault additional voltage source of zero sequence network,changing the system transient current ".4.The transient differential equation is established based on the fault transient equivalent circuit of resonant grounding system.The characteristics of zero sequence voltage and current are studied on state of under damping and over damping.Then,scheme of single phase grounding fault location based on zero sequence characteristic in distribution network with IIDGs is proposed.Finally,the resonant grounding distribution network model with IIDGs and the traditional distribution network model are built in RTDS.The distribution of zero sequence characteristic of each feeder terminal is tested based on MATLAB to verify the effectiveness of the proposed fault location scheme under different fault inception angle and transition resistance.