Performance characteristics of a doubly-fed generator on a test-rig with full-scale converter-based grid emulator

One key factor for a successfull penetration of wind turbine (WT) products into the market is certification. For the development and certification purpose, a 1 MW test-rig for WT nacelles has been developed at RWTH Aachen University which offers the possibility of WT testing with emulated environmental conditions. In this paper, the performance characteristics of a doubly-fed-generator (DFG) on the developed test-rig is discussed. Firstly, the effect of filter impedance of the grid emulator on the controller performance is analyzed under normal grid conditions. Secondly, the transient characteristic of a DFG WT considering the grid emulator setup is identified. A simulation is performed to verify the analysis. Under normal grid condition, the impedance of the grid emulator does not influence the controller of the DFG WT significantly. For fault-ride-through (FRT) tests with a grid emulator, only the series inductive elements of the grid emulator's filter influence the transient characteristic of the DFG WT. The developed 1-MW test-rig fulfills the technical requirement for FRT test in terms of the grid impedance.