Research On Optimal Planning Of The Distribution Network With Distributed Generation

Recently, the application of Distributed Generation (DG) increases intensely. Compared to the traditional electric power supply and distribution method characterized by large generator, large grid and high voltage, DG can provide power in a more efficient, clear and secure way. The combination of centralized power supply method and DGs is considered as the best solution for the problems of the traditional power grid. The presence of DGs in the distribution network can significantly produce economic and environmental benefit, such as reduce line losses and power demand, cut down the pollution of contaminants and greenhouse gases. However, improper design and planning of the introduction of DGs can bring negative effects, such as increasing line losses, making bus voltage out of limit, to the safe and stable operation of the distribution network. Consequently, in order to maximize the benefit and avoid the adverse effect, reasonable planning of the type, location and size of the DGs installed in the distribution network should be made under the condition of the safety and stability of the distribution network. Towards the optimal planning of DGs in the distribution network, the work of the thesis spread in the following aspects.Firstly, typical distributed generation technologies and their feature are introduced. The Newton-Raphson method based power flow calculation algorithm with DGs is proposed, and the effectiveness of the algorithm is verified on a real case. Based on quantitative analysis, the influence of DGs on the distribution network is studied, including the influence on line losses and voltage profile.Secondly, considering the DG installation location and size, the DG planning model aiming at minimizing the line losses is built with the constrains of bus voltage limit, branch current and DG penetration level. Based on the structure characteristic of radial distribution network, an EO-based solving strategy is proposed, and the adopted EO algorithm is modified to improve the algorithm performance. The algorithm is tested on real case, and the result shows that the installation of DGs can effectively decrease the line losses, and the algorithm performance test is carried out to show the superiority of the modified EO algorithm.Finally, considering the time varying nature of different types of loads and DGs, the Net Present Value (NPV) based DG planning model aiming at maximizing the financial income is built, according to a comprehensive analysis of the income and investment of DG installation from the economic angle. Based on the modification of basic PBIL algorithm, an improved Estimitation of Distribution Algorithm based solving strategy is introduced. The proposed algorithm is tested on IEEE-33bus distribution system, and the result shows that the installation of DG can produce substantial economic benefit. Algorithm performance test is conducted to show the superiority of the proposed algorithm.