The wind turbine generator system requires a power conditioning circuit called power converter that is capable of adjusting the generator frequency and voltage to the grid. Several types of converter topologies have been developed in the last decades; each of them has some advantages and disadvantages. Mainly two converter topologies are currently used in the commercial wind turbine generator systems. Most of the proposed converters require line filters and transformers to improve the power quality and step-up the voltage level, respectively. These heavy and bulky components significantly increase the tower construction, and turbine installation and maintenance costs. Recent advances in power semiconductors and magnetic materials have led to the development of new structure of converters, which would be a possible solution to reducing the size, weight, and cost of power converters. In this chapter, a comprehensive study of power converter technologies, current research and development is conducted.