Research On Service Restoration And Island Partition Of Distribution Network Considering Precise Load Control

With the development of economy and the improvement of people’s living standards,the reliability requirement of power system is also increasing.Due to natural disasters,power component failures and so on,power outage is inevitable in distribution network.Service restoration and island partition can restore power supply to the load in the non-fault blackout area after fault isolation,reduce the load interrupted and improve the reliability of power supply.To solve the problem of insufficient power supply capacity in distribution network under a severe fault,a service restoration strategy considering precise load control is proposed.The strategy uses genetic algorithm and second-order cone relaxation technique to carry out bilevel programming for network reconfiguration and unserved load.Considering the peak value of different types of load and the minimum output of different types of distributed generation appearing at different times,the unserved load after fault is further reduced.A new mutation operator,which can satisfy the radial network automatically and search the network more effectively,is proposed to solve the problem that crossover and mutation of genetic algorithm produce a large number of infeasible solutions.The modified IEEE33 bus system is used to validate the feasibility of the proposed method under three kinds of fault conditions.Because the total output of DG connected in the distribution network is generally less than the total load,the distribution network has to cut off part of the load after losing the superior power supply and restore power supply by dividing it into several isolated island areas.To solve this problem,a two-step method for island division is proposed.Firstly,a radial network connecting all nodes is constructed.Then,several branches are disconnected to divide the connected radial network into several subnetworks,which are still radial.By introducing virtual power flow auxiliary variables,the annular islands and the islands formed by all controllable loads are excluded from the feasible region.The operation mode of partially precise controllable load is divided into three kinds,and the mathematical model in the third type is constructed.The island partition is constructed as a mixed integer linear programming model,which considers the constraints of active power balance,reactive power balance and voltage amplitude.The effectiveness of the proposed method is verified by three numerical examples: static island division,multi-period dynamic island division with controllable load and multi-period dynamic island division without controllable load.