Nonlinear partial feedback linearizing controller design for PMSG-based wind farms to enhance LVRT capabilities

In this paper, the nonlinear partial feedback linearizing control scheme is employed for the machine-side converter (MSC) and grid-side converter (GSC) in a permanent magnet synchronous generator (PMSG)-based wind farm. The main control objective is to ensure the low-voltage ride through (LVRT) capabilities of the wind farm over a wide range of operating points. The detailed dynamical models of the MSC and GSC are considered to employ the partial feedback linearization scheme which linearizes these models in such a way that the feedback linearized systems are independent of operating points. At the same time, the desired control objectives can be achieved by using any linear control scheme and the proportional integral (PI) control scheme is used in this paper to obtain linear control inputs for these feedback linearized systems. The control objectives are selected as the output currents of the GSC in the dq-frame and the same for the MSC as the appropriate regulations of these properties ensure the LVRT operation of the PMSG-based wind farm. Simulation results are carried out on a grid-connected PMSG-based wind farm to evaluate the LVRT capabilities of the proposed control scheme under a severe three-phase short-circuit fault at the point of the common coupling. The performance is also compared with a conventional PI controller.