Research On Distribution Network Reconfiguration Method Considering Distributed Power Supply

With the development of the smart grid in recent years, distributed generation represented by the renewable energy sources such as wind power, photovoltaic power generation had been connected into power distribution network, however the distribution network operation state and control mode would be changed tremendously. The domestic and foreign researchers have done much research in the grid-connected DG impacts on the power system, but few of them studied on the distribution network reconstruction and service restoration after fault with large-scale DGs connected, to say nothing of the research on how to use the planned DG islanding resonablly to restore the service of the outage area with no fault under premise of ensuring the reliability of power supply of the important loads.So the study on this area has an important theoretical. In this dissertation, the power flow algorithm for the distribution network with multiple DGs and distribution network static reconfiguration, failure recovery with DGs has been studied intensively. The contributions of this dissertation are summarized as follows:(1)In the respect of power flow algorithm, the distributed generations have been divided into four node types, such as PQ, PV, PI and PQ(V), and the power flow model for each node type has been built. On basis of traditional power flow algorithm and with the combination of the power flow model, a new power flow algorithm which applies to the distribution network with multiple DGs has been proposed. The feasibility of the algorithm is validated by IEEE33example.(2) In the respect of distribution network static reconfiguration, firstly, considering the generating cost the capacity of DGs, replication dynamic used to reduce the cost of the dispatch of DGs has been proposed. Secondly, through the combination of the Minimum Spanning Tree Algorithm and the Heuristic Algorithm, a heuristic reconfiguration approach for distribution network reconfiguration which aims to minimize active power losses has been proposed. The proposed approach includes three solving processes:the preliminary optimization process on the basis of the Minimum Spanning Tree Algorithm, the quadratic optimization process on the basis of the new heuristic evaluation rules and the correction process. The preliminary optimization process on the basis of the Minimum Spanning Tree Algorithm cover the shortage of heuristic reconfiguration algorithm which relys on the initial network topology, meanwhile, on the basis of the preferable initial solution and the new heuristic evaluation rules, the candidate switches needed to evaluate reduce significantly and the computational efficiency improves greatly. (3) In the respect of the distribution network failure recovery, distribution network reconfiguration with DGs has been divided into two respects:the distribution network failure recovery in DG island and the distribution network failure recovery out of DG island. As the distribution network failure recovery in DG island, at first, set the importance of load and the cost of DGs the branch as weight, and build graph theory model. Then the partition result of all DG island is obtained at the same time by the successive shortest path algorithm, so that more important load in the outage area with no fault are restored with considering the economic factor of DGs. As the distribution network failure recovery out of DG island, in order to confirm the faulty section, the failover tree is built. Then the switchs in the outage area with no fault are divided into operational switchs and non-operational switchs. The calculated quantity will decrease by only considering the operational switchs. In order to guarantee the quality of failure recovery, the heuristic rulers of the switchs is proposed to confirm the order of closing the resume switchs and in order to guarantee the minimal active power losses of the system and the minimal number of console switchs after failure recovery, the number of the disconnect switch is confirmed based on the approach of distribution network static reconfiguration.