| With a high penetration of intermittent distributed generators(DGs),the uncertainties and fluctuations in active distribution networks(ADNs)are exacerbated and further coupled in the networks.It brings enormous challenges on system operation and puts forward a higher requirement for the operational flexibility of ADNs.In order to express the ability of ADNs to deploy its CRs to respond to the change of operation states,the concept of operational flexibility emerged.Operational flexibility is seen as a link between diverse operational requirements and flexible adjustment capabilities of CRs.Under the framework of operational flexibility,multiple types of operational optimization problems can be reinterpreted,which provides a new perspective for the operation of ADNs.The main contributions of this thesis are summarized as follows:1)The definition of operational flexibility of ADNs is proposed,including node flexibility,network flexibility and system flexibility.Based on the above definition,the operating scenarios of ADNs are divided into two types: flexible operation scenario and insufficient operation scenario.The evaluation indexes of system flexibility are proposed including: flexibility provision(FP),flexibility availability(FA),flexibility shortage(FS)and flexibility improvement(FI).2)Region-based mathematical formulation of operational flexibility is proposed,which can be expressed as regions of operational flexibility(ROFs)for flexible operation scenarios.The quantified calculation method of operational flexibility of ADNs is proposed and the numerical solutions of operational flexibility are solved based on Monte Carlo simulation.Plane of operational flexibility is proposed to intuitively quantify and visualize operational flexibility.By linear mapping the ROFs in the high-dimensional state space to the two-dimensional plane of operational flexibility,it is possible to effectively visualize whether the state of operational flexibility can meet diverse operation requirements.3)Applications of operational flexibility are elaborated under a unified framework of quantifying operational flexibility in different operation scenarios.From the prospective of operational flexibility,diverse operation issues are reinterpreted.Traditional optimization problems can be seen as the change of ROFs in the state space.Furthermore,through the visualization of FP and FA under different operation requirements,a new analytical perspective for the dispatchers are provided.4)For insufficient operation scenario,in order to generically quantify the power imbalance of ADNs,a quantified analysis method of FS is further proposed.Aiming at improving the flexibility of distribution networks,various schedulable resources are incorporated into the unified analysis framework.Through the coordinated cooperation of various CRs,the load shedding and curtailment of DGs are effectively reduced.Therefore,the FS is reduced. |
