Design and simulation of a wind energy conversion system based on doubly fed induction generator and back-to-back modular multilevel converters

Wind energy is one of the most growing renewable energy types in the world. Doubly fed induction generator (DFIG) based wind turbines have been used for more than two decades. Modular multilevel converters (MMC), on the other hand, have been initially proposed for high voltage direct current transmission for the purpose of long distance huge power transmission. Voltage levels even up to 100 or more at the output can be obtained using many cascaded power semiconductor bridges in each phase. The major benefits of MMC are well-dropped harmonic distortion at the output and significant voltage rating reduction of power semiconductors. In this thesis, the potential benefits of utilizing a back-to-back MMC system for a DFIG based wind energy conversion system connected to main grid has been investigated by simulation studies. The dynamic performance of the current vector control scheme has been tested by applying unit step-changes which applied to the reference signals of the controllers. Many simulation studies have been designed to verify the simulation model of back-to-back MMC based DFIG wind energy conversion system.