Research On Intentional Islangding And Day Ahead Schedule Optimal Dispach Of Active Distribution Network

It is widely accepted that renewable distribution generation (DG) and microgrid(MG) units will be the key to a sustainable energy supply and development, since they are small-scale、low carbon、 non-conventional and/or renewable energy source. Moreover, with renewable energy technology improving, continuous growth of penetration and application of DG and MG, electricity distribution networks are moving from passive to active networks. However, the intermittent nature and the uncertainties associated with the renewable resources, bi-directional flow of MG and interactive dispatching with distribution networks create special technical and economical problems in the tradition distribution system.The objective of the work proposed in this thesis is to tackle some of optimal dispatching strategies of active distribution network (ADN) for Power Company. The study, that include calculating the transmissions and high voltage(HV)distribution systems losses caused by medium voltage (MV) node loads, optimal dispatching schedule of ADN for DG and MG concerning the losses mentioned above, and optimal dispatching methods for restructuring the island are discussed in the paper.Firstly, the transmissions and high voltage (HV) distribution systems losses caused by node loads are calculated in this work. The algorithm of loss allocation coefficient based on power flow is present in this paper. Furthermore, a real transmission and HV distribution system are used for calculating the load node losses and the correlation among the load node losses, the load node losses rate and distance from load node to power supply resource. The results showed that the transmissions and high voltage (HV) distribution systems losses was determined mainly on the node load size in HV distribution network, correlation coefficient is0.97or more, while correlation coefficient is only0.092between the losses and distance. However, losses caused by the node load size in MV distribution network was depend mainly on the distance between node load and power supply resource, the correlation coefficient can be more than0.94, while the correlation coefficient between the load size and the loss is only0.025. This conclusions and the algorithm proposed in the paper are of importance for power companies to reduce transmission and distribution costs and select MV distribution line correctly in which DG and MG can be connected.Secondly, The Day Ahead schedule model, in which the objective is to maximize the interests of Power Company, is put forward in the thesis. The transmissions and high voltage (HV) distribution systems losses was considered in the AND schedule model for the first time. The government Compensation policy trends were taken into account in the model. The analysis was carried out considering an IEEE33-bus distribution system connected in the real transmission and HV distribution system with different load levels and penetration levels. The work clearly demonstrates that in the loss sensitive node, the result of AND schedule is to maximize the output of DG and MG, while in the loss insensitive node, the best penetration can be given by the AND schedule model.Thirdly, the method based on reserve energy at risk is used to assess MG power supply capacity in the paper. A multi-objective optimization model for restructuring intentional island is established considering equality constraints of linear relationship between MG output and confidence level of reserve energy at risk. An algorithm based on DFS and BFS is presented to get No inferior solution. Euclidean distance between the acceptable level and ideal acceptable level vector is used to get advanced solution. IEEE69-bus distribution system as example has been verified the model and methods.At last, the algorithm of loss allocation coefficient and The Day Ahead schedule model maximizing the interests of Power Company proposed in the thesis are applied real system in Beijing local power network. Integrated network loss rate were calculated and real interests of Power Company was obtained by using the cable network and the overhead network.