Research On Three-Phase Power Flow Algorithm For Distribution Network With Distribution Voltage Regulator

Distribution network three-phase power flow algorithm is the basis of distribution network analysis and the main part of distribution management system.With the development of the power system,the problem of the asymmetry in three-phase parameters and the imbalance in three-phase load are becoming more and more prominent.When the distribution network uses the single-phase power flow algorithm,a large of calculation error will be presented.In our country,the medium voltage distribution system generally adopts the isolated neutral operation mode,and the existing three-phase power flow algorithm is aimed at the neutral grounding distribution system.Therefore,it is of great theoretical significance and practical value to establish a three-phase power flow algorithm for the isolated neutral distribution system.The distribution load can be divided into three types:constant power load,constant current load and constant impedance load.For the isolated neutral distribution system with constant impedance load,uncertain neutral point voltage,transforming wye distribution load into delta distribution load by using star-delta transformation,establishing a three-phase power flow algorithm model and designing a three-phase current-injection Newton power flow algorithm for the distribution network with constant impedance load.It also solves the singular problem of the admittance matrix of the transformer in the isolated neutral distribution system with the method of adding a small capacitor from transformer node to ground.For the nodes that their voltage level can’t meet the requirement of the distribution network three-phase supply voltage,their voltage could be adjusted by using a three-phase distribution regulator in the distribution network.Establishing the mathematical model for both the single-phase distribution regulator and the three-phase distribution regulator.The calculation method and adjustment mode of the distribution regulator tap are derived in detail.Finally,designing a three-phase power flow algorithm for the distribution network with three-phase distribution regulator.The contrastive analysis is carried out through 3 3-bus system.It is proved that the designing three-phasse power flow algorithm has effective convergence,good accuracy and fast calculation speed.The voltage level can be improved effectively by using the distribution regulator,and make the meet the requirement of three-phase supply voltage of the distribution network.