A Review on Dynamic Equivalent Methods for Large Scale Wind Farms

An accurate model of large scale wind farm is demanded for researches about the impacts on the power grid. The total number of wind energy generators is so large that the detailed model of wind farm is computationally prohibitive. Dynamic equivalence can significantly reduce system order with the major characteristics retained. So the aggregation of large scale wind farm is inevitable. An overview of dynamic equivalent methods has been made for wind farms consisting of the widely used wind generators such as the doubly fed induction generator (DFIG) or the squirrel-cage induction generator (SCIG). The dynamic models of DFIG and SCIG and the mechanisms are briefly introduced at first. The wind energy generator is compared with induction motor to show the differences and similarities. Next, the possibility of the existing dynamic equivalent methods such as coherency-based method, parameter identification method and modal equivalent method to be used in wind farm aggregation is studied. The clustering criterions and model validation of wind farms are investigated. The feature and shortcoming of the re-scaled power capacities method are also discussed. At last, some suggestions are given for future equivalent researches of wind farms.