Application of variable frequency transformer (VFT) for grid interconnection of PMSG based wind energy generation system

Conventional grid connected permanent magnet synchronous generator (PMSG) based wind turbine generator (WTG) incorporates sophisticated power electronic control systems which produces harmonics and deteriorates the quality of the power supply. Recently, a new technology i.e. variable frequency transformer (VFT) has emerged as a flexible ac link to transfer power in-between asynchronous power grids. Hence, this paper aims to explore the possibility of grid integration of PMSG based WTG using VFT. The proposed scheme does not employ any power electronic based interface for grid integration of PMSG based WTG. To validate the proposed scheme, a simulation model has been developed under MATLAB/Simulink environment. A series of studies on power flow from the PMSG to the grid using VFT at different PMSG speeds has been carried out with this model. Moreover, the response characteristics of power transfer plots under various torque conditions are obtained. Further the efficiency, THD of output voltage and current have been compared with the conventional system. The proposed system is having almost the same efficiency but with negligible THD. The cost analysis of both systems has also been carried out. From the cost analysis, it is observed that the proposed system is cheaper than conventional system.