Research On Uncertain Power Flow Calculation And Operational Risk Analysis Of Active Distribution Network

Active distribution network,as the core of Energy Internet,with requirements of active sensing,active scheduling and so on,needs to be percepted accurately about uncertains of distribution energy resouces based on its complex grid structures and elements,and current operation status and forecasting operational risks of the system needs to be rapidly evaluated which guides the operation and scheduling.This paper proposes a D-S theory based uncertain power flow calculation method and a operational risk analysis model of active distribution network which guides optimal scheduling of distribution network.By comprehensively analyzing uncertain input variables of active distribution network,variables are divided into probabilistic and probabilistic ones and a uncertain power flow calculation model is established based on the D-S(evidence)theory.Probabilistic variable model adopts unscented transformation to probabilistic analysis,while possibility distribution adopts a-cut set to fuzzy analysis.By combining two kinds of uncertainty through evidence theory,the uncertain power flow model of active distribution network with probabilitic and fuzzy uncertain inputs can be obtained quickly.Based on uncertain power flow results,an operational risk analysis model is established.The operational risk is expressed as the product of the operational risk probability and the operation risk consequence;take over-limit probability of node voltages and branch active powers as the operational risk probability index,as well as and the outage cost calculated by ratio of output value to unit electric energy consumption and percentage of load-cut as operational risk consequences,and then operational risk index can be obtained,.taking into the probability and severity.A two-stage scheduling model considering operationals risk is builted by introducing the operational risk index into the scheduling and operation of active distribution network.Through the two-stage uncertainty programming theory,the objectives of the first stage and the second stage are respectively the least scheduling cost and the lowest risk,and the load loss risk of the risk cost corresponds to the risk index of the operational risk model.The risk value is added to the overall scheduling objective as a penalty function,and scheduling outputs of controllable distributed energy resources are calculated by prime-dual interior point method,which takes the safety and economy of the active distribution network into account.Numerical examples are demonstrated in the improved IEEE 33-node distribution network to conduct uncertain power flow calculation,operational risk calculation and two-stage scheduling,which verify the speedability and the effectiveness of proposed algorithms and obtain practical value to the comprehensive perception and operational risk decision-makings of distribution network.