Research On Coordinated Recovery Method Of Transmission And Distribution Network Considering High-proportion Of Distributed Generation

The increase in the proportion of distributed generation and the continuous deepening of power market reforms have increased the risk of large-scale power outage to a certain extent.At the same time,the increasing permeability of DG in the power grid also makes the structure of the distribution network and its role in the system restoration after the blackout change profoundly.The traditional power system restoration theory is encountering new challenges.In the research of transmission and distribution network restoration after blackout,transmission network and distribution network are usually decoupled into two research objects.However,in the context of high proportion of DG access,the interaction between transmission network and distribution network which is more prominent in the system restoration can not be treated separately by simple equivalence.In order to solve this problem,this paper studies the coordinated restoration method of the transmission and distribution network under the consideration of high proportion of DG access.Through the formulation of scientific and reasonable scheme,it coordinates the restoration of the transmission and distribution network of the power system with high proportion of DG access,so as to speed up the restoration process of the system after the blackout and reduce the loss of the blackout.The main contents of this paper are as follows:(1)Study on the ability of DG auxiliary power grid black start.The characteristics of black start power and different kinds of DG are analyzed.Different evaluation indexes are extracted from three aspects: time,stability and recovery ability.Furthermore,entropy method is used to determine the weight of each evaluation index,which is combined with the grey target theory.By solving the bull’s eye center,the priority of black start ability of different types of DG auxiliary power grid is obtained,and the black start ability of different types of DG auxiliary power grid is analyzed.(2)Study on the influence of active distribution network with high proportion DG access on network reconfiguration.Considering the high proportion of DG access in active distribution network and the less demand of load in distribution network,the distribution network can realize power return and realize the power support of active distribution network for transmission network restoration.A multi-objective optimization model considering the total generating capacity and recovery time of network reconfiguration is established.The model is solved by combining the non-dominated sorting genetic algorithm and the variation coefficient method.Finally,the influence of active distribution network access on transmission network reconfiguration is analyzed with the example of New England 10-unit 39-node power system and IEEE33 node system.(3)An optimization method for coordinated restoration of transmission network and distribution networks with high proportion of DG access is proposed.According to the different effects of DG output in different stages on the restoration of transmission network and distribution network after blackout,the coordinated restoration of transmission and distribution network is divided into stages.Considering the transmission network layer,generation capacity,load recovery capacity and load loss of distribution network layer,a hierarchical optimization model for coordinated recovery of transmission and distribution network under high proportion DG access is established,and the DG output in different recovery stages is coordinated by introducing penalty function.Combined with hierarchical sequence method,backtracking algorithm and greedy algorithm,the optimization model of coordinated restoration of transmission and distribution network is solved.The example is given to verify the correctness and effectiveness of the proposed strategy and method.