Direct current grid‐based doubly‐fed induction generator wind turbines: Real‐time control and stability analysis

Commonly, a simple topology consisting of a single diode-rectifier and pulse-width-modulation (PWM) converter is used for the connection of the doubly-fed induction generator-based wind turbines (DFIG-WTs) to the DC grid, in which the rotor-side converter (RSC) and the stator diode-rectifier are linked to the common DC bus. But, this topology suffers from less flexibility due to the requirement of matching the stator nominal voltage with the DC grid. Hence, in this paper, a buck converter is added to the DFIG-WT topology and two methods are proposed to control the power converters, where in the first one, the RSC regulates the active power and stator flux linkage, and in the second one, the RSC regulates the DC bus voltage and stator flux linkage. Then, the small-signal stability and the performance of the DFIG-WT system with the mentioned control strategies are compared analytically and through the off-line simulations. At last, a real-time hardware-in-the-loop (HIL) emulation-based OPAL-RT is carried out to investigate the performance of the proposed control methods from a practical perspective.