A Multilevel Converter with Reduced Number of Switches for Grid Connection of Permanent Magnet Synchronous Generator Based Variable Speed Wind Turbine

Abstract

In this paper a cascaded multilevel converter with reduced number of switches is proposed for grid connection of a direct-drive Permanent magnet synchronous generator (PMSG) based variable speed wind turbine to improve the waveform quality of the converter output voltage and current. Therefore, the bulky passive grid filters can be reduced or even removed. The basic topology and control strategy of the proposed converter are presented in detail. The generator is connected to the grid by means of a diode rectifier, an intermediate buck-boost dc-dc converter, and a multilevel converter with reduced number switches. The grid side multilevel converter is controlled to obtain high efficiency under different load conditions. Vector control of the grid-side multilevel converter featured with output voltage and frequency controller that is capable of handling variable load conditions. The operation and performance of the proposed system have been evaluated by Matlab/simulink. Simulation results shows that the controller regulate magnitude and frequency of voltage to match with the grid under varying wind and load conditions.