Research On Source-load Coordinated Restoration Of Isolated Grid After Blackout

With the rapid development of economy,the technology of AC-DC transmission and power grid interconnection have been improved.A large number of high-voltage electrical equipments and large capacity generating units are introduced into the system,which leads to the complexity of modern power system.As a result,the ability to resist large disturbances is also being weakened.The isolated grid which is splitting has become an important part of the power system once the dispatcher does not operate properly or the protective device is incorrectly operated after serious fault.Even worse,it even leads to a large scale blackout or the collapse of the whole system.In order to accelerate the restoration process of the isolated grid,balance the active and reactive power and achieve source-load coordinated restoration,the following research on source-load coordinated restoration of isolated grid after blackout is carried out:(1)A source-load partitioning method for isolated grid is studied.First of all,the black-start-unit(BSU)is determined.Then,the partition method based on network topology is studied with the BSU,in which the number of partition is equal to that of BSU.The shortest time of restoration is set as the objective function,considering the constraints of balance between partitions.The complex network in graph theory are applied to solve the model.After that,non-black-start-unit(NBSU)and load are divided into corresponding partitions.The purpose of isolated grid partition is to realize the parallel restoration,speed up the restoration process and reduce the loss of power outage.The results of the study have laid a foundation for path optimization for black-start.Finally,the validity and accuracy of the proposed method are proved by the New England 10-unit 39-bus system.(2)A source-load path optimization method for isolated grid considering evaluation of node weight factor is proposed.Firstly,a set of indictors for line and unit is defined.Then the index is classified and weighted by DEA/AHP,in which data envelopment analysis(DEA)is combined with analytic hierarchy process(AHP).The optimal black start topology is built with the maximum weight factors of nodes.After that,backtracking algorithm is introduced to calculate the specific black-start path from the optimal tree topology,where the target is to maximize the weight factor of path.The optimization algorithm can effectively reduce the path search space and has high robustness.Finally,New England 10-unit 39-bus system is used as an example to verify the effectiveness of the proposed algorithm.(3)An optimal source-load coordinated restoration method that is based on information gap decision theory(IGDT)is proposed.Firstly,the time-domain restoration characteristics of BSU,NBSU,and load are described with analysis of double uncertainty.On this basis,a coupled multi-objective optimization model is built with double uncertainty,in which source-load coordinated restoration is realized.Then,IGDT is adopted to convert the uncertainty optimization model to a certain one with robustness,which tolerates the most uncertainty and still meets the desired requirement.Finally,the optimization model is solved by non-dominated genetic algorithm II(NSGA-II).The effectiveness and robustness of the proposed method is further illustrated through a case study based on the IEEE 39-bus system.