Wind power produces environmentally sustainable electricity and helps to meet national energy demand as the amounts of non-renewable resources are declining. The development of the WECS can be seen with development in power electronics technology. Currently, two types of major generator used in WECS these are DFIG and the PMSG. Both variable oprational speed are used in wind turbine. Because, its high performance, reliability, controllability and high power and voltage capabilities, multilevel converters have become a popular option for multi-MW WECSs. This paper focuses on the application of back to back modular multilevel converters in a DFIG and PMSG based WECS. A comparative performance analysis of the two systems based on power quality, active, reactive power, and MMC dynamics is presented. The comparison is based on simulation results created in MATLAB/Simulink software.