Study On Fast Simulation Of Three-phase Unbalanced Power Flow In Active Distribution Networks

In order to cope with a large number of intermittent distributed generations in distribution network,the active distribution network(ADN)with active control and management capacity emerged,and become the main direction of future development of smart distribution grid.To meet the changing needs,active distribution network must be flexible enough to react to the decisions made by users and and increasingly sophisticated micro-processing agent.Power flow calculation,as one of the basic simulation tools of the active power distribution network,it requires the ability to quickly and accurately calculate three-phase unbalanced load flow in distribution network,and realize super real-time simulation function,However,the traditional phase component method is not suitable for ADN fast simulation parallel computing.In order to meet the requirements of fast simulation in ADN.A improved sequence components method is proposed that can be efficiently applied to parallel computing of three-phase unbalanced power flow in ADN.Firstly,the paper builds sequence components models of ADN components based on compensation method.A variety of distributed generation(DG)sequence components are established that can cope with different types of nodes as PQ or PV.And adds virtual line to simplify sequence components of the open phase,it can build unified sequence components models for entire distribution networks lines.For transformer,phase transformation technology is a good way to solve,apply it to the sequence component flow calculation,it can be achieved for all transformer branch for integrated treatment,to avoid a large number of derivation.To accurate calculation power flow in distribution networks,the paper builds sequence components models of different connection loads.Secondly,unbalanced distribution networks is decomposed into three sequence networks and compensation parts.Positive sequence network is an active network,Positive sequence power flow are the same as those used by any single phase power flow algorithm.Negative and zero sequence network is a passive network,the negative sequence and zero sequence network is calculated by nodal voltage equations.After three decoupling sequence network node admittance matrix sparse degree is bigger,sparse technology can be used in the three sequence network.Parallel computing can be used for three decoupled networks,it reduces the computational scale,saves storage space,and greatly improves the computing speed.Finally,the simulation results of test examples are provided to demonstrate the correctness and effectiveness of the proposed method.