A Wind Turbine Conversion System Featuring Grid Forming Control

A wind farm may be susceptible to small-signal instabilities due to interactions between wind turbine (WT) grid-side converter (GSC) and a weak grid. This paper introduces a WT conversion system that facilitates grid forming (GFM) control of WT GSC without use of battery system. The proposed scheme consists of a 9-phase hybrid generator (HG) whose output is rectified by a passive rectifier and connected to the GSC before interfacing to the wind farm AC collector grid. The HG has a dual rotor topology, a permanent magnet (PM) rotor and a wound field (WF) rotor. As the wind velocity varies the rectified DC-link voltage is controlled to maintain fixed around its nominal value by adjusting a DC current into the HG WF. This constant DC voltage is then converted to fixed frequency and voltage at WT output, thus providing a GFM solution control and undertaking the stable behavior during weak grid condition. The GSC controls the WT output current. Analytical models for the proposed WT conversion are derived, and simulation studies are performed under different conditions to verify the effectiveness of the proposed scheme and control strategy.