Research On Fault Location In Distribution Network With DG Based On Nonlinear Impedance Model

Research on fault location has always been an important issue for the power system. With the development of distributed generation(DG) technology, the trend of distributed resource(DR) connected to the conventional grid is becoming more and more obvious. As a result of the DG access, the traditional distribution system characterized by radical network evolved into a multi-source one, which made the feeder protection and fault location analysis based on the feeder terminal unit(FTU) of the distribution automation become more complex. Fundamental changes have taken place in the structure of the traditional distribution network, while fault location methods must adapt to the change,which is a big challenge in distribution network with DG. Research on fault location method in distribution network with DG has an important role in restoring power and reducing power loss, also it has important application value.Aiming at the shortcomings of the existing fault location methods with DG in distribution network, research on precise fault location method in distribution network with DG was carried out in this paper. A new fault location method based on the nonlinear impedance model in distribution network with DG was proposed in this paper,which taked into account that the randomness of measurement data, the nonlinearness of ground resistance and the network load.Firstly, complex correlation Thevenin equivalent and strong tracking filter(STF) was used to obtain the three-phase impedance model of main source and DGs. Considering the nonlinear load, the system three-phase asymmetric impedance model was established.Secondly, analyze and extract the fault characteristics under the system model, then the fault section was identified by the fault characteristics of each node.Finally, on the basis of the three-phase asymmetric impedance model and fault section, the differential evolution algorithm with parameter adapted was applied to search for the minum fault characteristic value automatically, in which the fault distance and fault lines were as a variable and the fault characteristic value of fault node is the fitness function.The output is the accurate fault location result.The method proposed can overcome the measurement error caused by the uncertainty of the data, which make the system three phase impedance model be more consistent with the actual distribution network model. The simulation results show that the method has advantages of high ranging accuracy, strong robustness and fast computing speed, applicable to fast fault location of any distribution network with DG composed of the cable lines and overhead lines.