Evaluation Method Of Total Supply Capability Of Distribution Network Based On Reconfiguration Technology

With the rapid increase of users' demand for electricity and the promotion of grid intelligence,the importance of distribution network,as an intermediate link between the transmission network and users,has been raised to a new height.For a long time,the construction level of distribution network is relatively lagging behind,and there is a large development space in the future.How to make the construction of distribution network adapt to the demand of load has become an important research issue in the current development planning of distribution network.From the total transfer capability,the total supply capability index of the distribution network can accurately and intuitively reflect the existing carrying capacity of the distribution network under the existing construction and the load distribution it can support.The evaluation method of this index in the existing literature can not consider the situation of multiple transfers,so it has certain limitations and can not fully tap the power supply potential of the distribution network.The reasonable evaluation method of maximum power supply capacity should consider N-1 security constraints.When the fault occurs,the system completes the power supply recovery of the lost load through reconstruction.Further,in order to ensure the implementation of reconstruction,it is necessary to consider the relevant constraints,so as to formulate a reliable and safe switching sequence strategy.Under the above background,this paper carried out the following research contents:(1)The problems existing in the current evaluation method of total supply capability of distribution network are analyzed.In the process of modeling,the existing methods specify the transfer mode of outage load in advance,and only consider one time of transfer,which limits the flexibility of distribution network reconfiguration,and can not fully tap the power supply potential of distribution network.(2)In view of the above problems,the distribution network modeling method and distribution network reconfiguration technology used in this paper are elaborated in detail.On the basis of reconfiguration,a switch sequence optimization method considering process security is proposed to ensure the smooth implementation of reconfiguration results.Firstly,the improved binary particle swarm optimization algorithm is used to obtain the set of distribution network reconfiguration solution,and the coordinates of the invalid particles in the iterative process are modified randomly to improve the search efficiency.Then,the constraints that should be satisfied for loop closing and unwinding are presented,and the Thevenin equivalent model is applied to calculate the closing current.Finally,a recursive algorithm is proposed for solving the switch sequence optimization of distribution network reconfiguration considering process safety.Aiming at the invalid intermediate solution in the recursive process,binary coding is used to record the invalid intermediate solution,avoiding repeated calculation and improving the efficiency of the algorithm.The effectiveness of this method is illustrated by the analysis of standard and practical examples.(3)A evaluation model of total supply capability of distribution network considering multiple transfers is proposed.Firstly,a load path set is established based on path description mode.Then the total supply capability evaluation model of distribution network is established by taking the path on-off state as the variable,the maximum of the system load sum as the objective function and the N-1 security check condition of the distribution network as the constraint condition.Finally,the penalty function of N-1 check is designed,and the particle swarm optimization algorithm is used to solve the problem.The example case shows that this method can fully excavate the power supply potential of the distribution network.At the same time,we can get the corresponding power loss transfer strategy for all kinds of main transformer faults and solve the limitation of the traditional evaluation method.