| Distribution network generally operates open-looply and designs closed-looply, there are often a large number of sub-switchings and a small amount of contact switches in the distribution network, therefore, under normal operating conditions according to different load status of the network, we can change the opening and closing states of these switches to adjust the network structure, on one hand, it can reduces network losses, improve the economy of power system, on the other hand it can balance the load between the lines and transformers, eliminate overload and improve the quality of the supply voltage, this is the optimum reconfiguration of the distribution network. Reconfiguration of the distribution network is an important way to improve the economy, safety and quality of power system. In recent years, more and more distributed generations are access to distribution network. It inevitably brings some certain influence to the distribution network. Therefore, studying the distribution network reconfiguration with distributed generation has a high theoretical and practical value.Firstly, this paper describes the research status of distribution network reconfiguration and then discusses the types and mathematical models of distributed generations.Secondly, in order to solve the problem of power flow calculation of distribution network connected with various DGs, DG modes are constructed respectively according to the different features of different types of DGs, thus the nodes with DG are classified into PQ node, PV node, PI node and P-Q (V) node in this dissertation. In view that back/forward algorithm cannot cope with weakly meshed distribution network and PV nodes, this paper puts up the power correction equations based on reactance matrix and mismatch of voltage magnitude, proposes a method to correct reactive power of P,V-type distributed power. This paper presents a new power flow calculation based on superposition theorem when coping with weak ring network, the ring is divided into pure radial network and loop network, calculates power flow respectively, then superposition on the results; proposes the improved back/forward sweep algorithm, so that the branch trend in same level can compute parallelly, increases the calculation speed. Through the process, it makes power flow calculation for containing DGs network becomes simple, and then takes IEEE33 node system for example to verify the effectiveness of the proposed algorithm.On the basis of study the distribution network depthly and systematicly, this paper references and summarizes the results of previous research to improve the genetic algorithm (Genetic Algorithms, short GA) used for the reconstruction of distribution network. Introduces evolutionarily stable parameters in the algorithm, makes the population of the outstanding individuals maintained at a certain level. It has been exampled that this project not only keeps the variety characteristic, but also extends the searching space through mutation factor. So it’s easy to find the global optimized area, reduce the chance to draw into local optimized area. So the calculation time is reduced. In addition, this paper optimizes the chromosome coding scheme, according to the principle that the first end connected to the grid of branches outside the ring network switches and branch switches and isolated T nodes must be closed, certain switch is normally closed, they are no longer involved in network reconfiguration, effectively reduces the length of the chromosomeand increases the proportion of feasible solutions, improves the efficiency of the algorithm.Finally, taking the example of IEEE33 nodes and US PG & E69 buses system, this paper adds distributed generation to the two systems respectively, programs by the software of MATLAB R2010a, uses the genetic algorithm based on evolutionary stable strategy for distributed network reconstruction including distribution generation, the simulation verifies the feasibility of the proposed algorithm. |
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