Study On Self-healing For Active Distribution Network

Distribution network which is at the terminal of the power system directly plays an important role in supplying power to users and affects the power supply reliability and power quality.At the same time,with the development of new energy generation technology,the distributed generation penetration in the distribution network is increasing,and the challenge of distribution network security and stability which are caused by the randomness and volatility of distributed power becomes increasingly prominent.As one of the core characteristics of smart grid,self-healing which can effectively improve the safe of distribution network becomes the focus of attention at home and abroad in recent years.Although domestic and foreign scholars have done a lot of research in the field,there is still a lack of theoretical and practical.Therefore,the study on this area has an important theoretical and practical significance.The distribution network reconfiguration,fault location and service restoration are studied in this paper:1.The framework of active distribution network self-healing technology and related concepts is introduced.The latest research and development trend on network reconfiguration,fault location and service restoration is reviewed and summarized.2.The branch flow based network reconfiguration model is established,and a transformation and second order cone relaxation method which transform the original nonlinear problem into a second order cone problem are given in this paper.Using the ?-relaxation method,the second order cone constraint is linearized and transformed into a linear programming problem.Besides the linear flow based network reconfiguration model is established.Using optimal equidistance piecewise linear approximation method the quadratic loss objective function can be approximated by a piecewise linear function.Then the original problem is transformed into a mixed-integer linear programming model.Based on several test systems,above mentioned models,common heuristic method and artificial intelligence algorithm are used to solve the network reconfiguration problem to compare the algorithms'searching ability and solving performance.3.Network reconfiguration model considering uncertainty which is based on linear flow is proposed considering the uncertainty of load and distributed generations' output.Based on the following network reconfiguration model,a two-stage robust network reconfiguration is proposed in this paper.By introducing the C&CG algorithm,the two stage robust network reconfiguration model is decomposed into a master-slave problem which is a mixed-integer linear programming.The feasibility and effectiveness of the proposed method are verified by several numerical examples.4.State estimation model of active power distribution network based on FTU and PMU hybrid measurement is established,and unified method for transforming the parameters of hybrid measurement is presented.Then a fault location method and solving strategy based on hybrid measurement state estimation is presented in this paper.The fault location ability of the method is verified by a variety of fault scenarios' simulation.5.According to influence and role of the access of distributed generations on distribution network service restoration,this problem can be divided into two sub-problems,namely island restoration and residual network reconfiguration.Using the branch flow network reconstruction model the residual network reconfiguration model and the island restoration model is established.Based on the model mentioned above,a new two-step coordination strategy is proposed to realize the maximum load recovery and least unintentional islanding.The feasibility and effectiveness of the proposed method are verified by a numerical example.