Substation Optimization Planning Considering The Improvement Of Supply Capacity And The Access Of DG

Substation planning is directly related to the future of network spatial layout, the network investment, economy and reliability of power supply of regional power grid. It is an important subject in power system planning under the background of the meticulous planning; its related research conclusion will be an instructive suggestion for distribution system planning work. The research on substation planning has been relatively mature, but with the economic development of the city and the expansion of the load, the substation planning has appeared wasteful in the traditional investment, which could not meet the requirement of the distribution network construction. Therefore, based on 110 kV substation planning as an example, the researches on how to improve the utilization rate of transformer substation equipment, to reduce the investment cost of power supply, to guarantee the security and reliability of power supplies were deeply carried out. The research results are combined with substation planning theory to form an improved method of substation planning. The application of this theory is an important link in perfecting power grid planning and lays a solid foundation for the fine planning of distribution network. The main contents are as follows:1. Through the thorough analysis of the substation upfront investment, the factors influencing the cost of operation and maintenance and scrap stage; the cost of substations can be divided into direct costs and indirect costs. Direct costs refer to the investment cost of substations and low-voltage side lines in the early stage, which are easy to quantify. Indirect costs are related to such factors as geography, environment and society, it is not easy to quantify. Consequently, this paper summarizes the relevant indexes of 110 kV substation indirect costs and their quantitative criterion, and based on this, puts forward the comprehensive evaluation system of substation indirect costs. According to the improved osculating value method, the substation indirect cost factor is determined. Finally, the paper combines substation direct costs with indirect costs factors, constitutes the substation life-cycle cost calculation model. The model fully and accurately reflects the substation cost of all life stages, providing the decision-making basis for substation planning.2. Based on weighted Voronoi diagram of the substation planning theory as the foundation, further study of each link improvement strategy is carried out, the following improvements are proposed: studied weight adjustment strategy, improved the convergence speed and the results of planning; thoroughly analyzed the influence of the initial sites on planning results, proposed a new method for the optimization of the initial site based on improved K-means algorithm, and a numerical example illustrates the advantages of this method; as for the current situation of "prefer goal to the process" of substation planning, put forward the gap year substation planning scheme, perfecting the whole-stage substation planning work.3. Traditional substation planning determines the load rate of each substation based on transformer "N-1" principle, which does not consider the influence of the contacts between substations on substations load rates. Aiming at this problem, considering the contact lines and channels construction costs, established joint optimization mathematical model of total life cycle cost of substations and liaisons between substations. Based on this point, a joint optimal planning method of the substations and the contacts between them was put forward. In the principle of main transformers "N-1" and under the premise of meeting load demand, this method can reduce the substation planning capacity, improve the utilization rate of transformers to reduce the substation investment costs, which have important significance to the refinement of the distribution network planning.4. For future planning areas are facing massive access of distributed generations(DG), this paper, in accordance with the principle of constant power system reliability index before and after DGs access, proposes a DG capacity credit assessment method, and analyzes the influence of different load types on capacity credit, which effectively evaluated the credit of the DG capacity. On this basis, the paper combined DG capacity credit and substation capacity, put forward a substation optimal planning method considering a large scale DG access to planning area. This method can effectively plan the credit of DG capacity and reduce the substation planning capacity, thus further improved the level of refinement of power distribution network planning.