Study on the total harmonic distortion of a 5-MW wind turbine with modular multilevel converter and development of a demonstrator

This paper investigates the possibility of applying medium-voltage modular multilevel converters in 5-MW onshore wind turbines. The focus is on the reduction of higher order harmonics in comparison to classical 3-level medium-voltage converters. The simulation of the 7-level 5-MW converter shows that the harmonic limits in accordance with the actual grid codes can be met without an additional grid side filter. The paper starts with a description of the detailed grid and converter model parameters, followed by the grid compatibility simulation according to the standard grid codes. Subsequently, a setup of a 3-kV 350-kVA MMC demonstrator with commonly used low-voltage components is presented which will afterwards serve to verify the simulation results.