Distribution Network Planning With Distributed Generation

Distributed generation (DG) is predicted to play an increasing role in the electric power system of the future. A large amount of DG capacity conneted to distribution network will bring about the great influence on operation and planning of conventional distribution network. Therefore, the study on distribution network planning with DG is one of the hotspots in the power engineering research field. This dissertion concentrates on some critical problems in this field and the main innocations are shown as follows:(1) Combined with the typical load characteristic curve, a new method for substation planning with the consideration of DG for peak cutting is proposed to overcome the low utilization and unbalanced loading of main transformers in the conventional methods. Moreover, genetic algorithm based on Voronoi diagram can determine the optimal location, sizing and the service areas and provide an effective design method of substation planning.(2) Planning models of the novel distributution network are established from the different viewpoints. The planning model considering safety constraints takes the risks as the result of DG connection into account and increases the safety capability of distribution netwrok; Based on chance-constrained programming, the planning model considering stochastic character of renewable DG output is presented to evaluate the distribution network investment risk due to DG connected to distribution network; The multi-objective planning model is built to explore the tradeoff between the maximum penetration level of DG and distribution network investment. The iterative algorithm based on linear programming is adopted to maximize the DG capacity in the given network, while the improvedε-constraints approach is used in the optimization decision on the pareto optimal set; The planning model of distribution network integrated with DG, which aims to minimize the social cost, is transformed into a bi-level planning and provide a noval measure to allocate DG source in the mode of demand side management (DSM) and active management.(3) Spanning tree-based genetic algorithm (st-GA) to solve distribution network planning with DG is presented. St-GA with two specialized genetic operators can guarantee the topological feasibility and high heritability of each solution generated and overcome the deficiencies of existing GAs applied for distribution network planning. According to the topological characteristic of distribution network, the multistage distribution network planning can be transformed into a problem of searching the optimal target network with the minimum total costs in the whole planning horizon, which contains the message of each building stage for every candidate branch and its size.(4) Locational marginal capacity cost (LMCC) is introduced to reflect the forward-looking cost of nodal capacity and the degree to which nodal capacity is utilized. On this basis, DG connection criterion that the unit capacity cost of DG is less than LMCC at its candidate node is obtained to avoid the lower utilization of the existing power supply facilities, which provides a new tool to envaluate DG connection from the point of the view of enlarging capacity with DG.Analysis and comprarision of the study cases proves the feasibility, effectivity and practicability of this dissertion.