The Research Of Microgrid Reconfiguration Based On An Improved Grey Wolf Optimization Method

In the operation process of micro-grid,due to various interference systems,the micro-grid often deviates from operating states of reliable,safe,economic.Therefore,in order to enhance the reliability,security and economy of micro-grid,an improved gray wolf algorithm for micro-grid reconstruction strategy is proposed.The main contents of this paper are as follows:Firstly,a comprehensive vulnerability function considering the system electrical and structure is established,and a dispersion index of network micro source to measure the vulnerability of the system structure is proposed.Secondly,the micro-grid reconfiguration model is established.The reconfiguration model consists of three parts,the model of micro source and load,constraints and reconfiguration objectives.The decision variable is a combination of continuous and discrete variables composed of the power of network switch,micro source and flexible load.Then,the reconfiguration strategy of improved gray wolf algorithm is proposed.Aiming at the problem of non-radial network structure in the process of reconfiguration optimization,the reconfiguration strategy adopts the broken circle method to randomly generate radial structure as the network structure of the initial generation solution.The depth first search is used to identify,analyze and process the network structure,and generate the node traversal order.In the iterative process,the disconnected network structure with isolated branches is replaced by the radiation structure randomly generated by the loop breaking method.According to the order of traversal nodes,the forward and backward method is used to calculate the network power flow distribution of the system.Through gray wolf algorithm,step by step iteration,get the best reconstruction scheme.In addition,the multi-objective optimization process is divided into two stages.In the early stage of algorithm optimization,the Pareto optimal frontier solution set is found.In the later stage of algorithm optimization,according to the solution set of Pareto optimal frontier,a set of threshold value of each target index is determined as the boundary of the later optimization target.Only the solutions in the bounded domain are allowed to be selected as the better ones.The weighted objective function guides the search direction and selects the best one.Finally,the micro-grid modified from IEEE 16 nodes,IEEE 33 nodes and IEEE 69 nodes distribution network are taken as examples.These examples verify the correctness and feasibility of the proposed reconstruction strategy.