Research On Distribution Network Reconfiguration Based On Several Optimization Methods

Distribution network is designed as a closed loop and operated as an open loop,including many closed section switches and open connective switches. When mode ofthe switches are changed in someways, the structure of distribution network is changedtherewith, and it can achieve the target of balancing load, reducing loss and improvingvoltage quality.In mathematics, distribution network reconfiguration is a NP-hard high-dimensionalnon-linear multi-objective optimization problem with a great solution space, and it’sdifficult to get a good solution by using general optimization methods. Existingoptimization methods such as optimal flow pattern method, branch exchange method,particle swarm optimization, genetic algorithm, tabu search algorithm and improvedexhaustion, have room for improvements in computational efficiency and optimizationresults.Genetic algorithm is an type of evolutionary algorithm, with the feature ofparallel probabilistic search, and it doesn’t need derivation of the objective function, fitfor nonlinear optimization problem as distribution network reconfiguration. However, inexcisting genetic algorithm, too many infeasible solutions are generated in evolutionaryprocess, and the diversity of population gradually decline with evolution, which r estrictsthe efficiency of the algorithm. In the paper, a distribution network reconfigurationformula based on cooperative co-evolution algorithm(CCA) is proposed. It retains theoriginal advantages of evolutionary algorithm, and evolution operations in each loop areused to reduce the probability of generating infeasible solutions, besides, a "certain tree"method is adopted to restore the infeasible solutions, maintaining the diversity of thepopulation effectively.The best solution can be certainly got by improved exhaustion, but how to find aeffective heuristic rule and narrow the solution space of distribution networkreconfiguration is the key. In the paper, according to the common ground in differenttopologies of distribution networks, a division method is formulated, by which the wholesolution space of distribution network reconfiguration is divided into different subspaces,and a local optimization is used to find the optimal solution in each feasible subspaces.The number of candidates which need loss calculation is notably reduced, improving theefficiency.With a lot of Distributed Generation(DG) accessing to distribution networks, the flow and voltage of distribution network are greatly affected. In the paper, injectionpower of DG is treated as an optimization variable, to participate in distribution networkreconfiguration, and a comprehensive optimization formula of distribution networkreconfiguration and injection power of DG based on co-evolution algorithm is proposed,and a network topology and injection power of DG control scheme with low loss andhigh voltage quality can be got.