Real-time simulator based hybrid controller of DFIG-WES during grid faults design and analysis

This paper presents the significant contribution of the combination of both vector control and direct torque control (HC) strategies for DFIG based WECS. The DTC is applied to rotor side converter (RSC) to control the rotor flux and generator speed. It also controls both active and reactive power components indirectly. Whereas, VC is applied to grid side converter (GSC) to control the DC-link voltage and also to improve the quality of power supplied into the utility grid. The greatest advantage of the proposed control is that the DTC and VC are de coupling in nature, so that the rotor side control is independent of stator parameter variations. Especially, HC successfully tackles the problems related to voltage dip, LVRT and FRT. The simulations for the proposed VC-DTC strategy are carried out in MATLAB/SIMULINK environment and the results indicate that the proposed VC-DTC technique provides excellent dynamic response in terms of DC voltage and current transients, and smoothing of generator speed during grid disturbance. Further, the torque, flux and current ripples under steady state conditions are also minimized. The proposed HC doesn't require any auxiliary protection circuit, which indicates that the complexity of the control scheme is reduced during abnormal grid conditions. Finally, the real time simulation of the proposed HC strategy is carried out on OPAL-RT (OP5700) real time simulator. The simulation and RTS results demonstrate the superiority of the proposed SMC based HC when compared to the conventional PI controller based DFIG WECS.