Disturbance feedforward control for type-3 wind turbines to achieve accurate implementation of transient control targets during LVRT

Abstract

The existing low voltage ride-through (LVRT) control strategies usually modify the post-fault current reference to contain some transient and negative-sequence components, to achieve the controllable LVRT operating of type-3 wind turbine (WT) under severe grid fault. However, the modified current reference and post-fault electromotive force (EMF) disturbance behave as the multi-frequency (i.e., 0-, 50- and 100-Hz) components in the synchronous dq-frame, thus the classic PI controller-based current control cannot provide zero-error tracking of the aforesaid reference, and leading to the inaccurate implementation of transient control targets. To solve this problem, based on the relationship between the modified current reference and post-fault EMF, an improved disturbance feedforward control is proposed to simultaneously suppress EMF disturbance and improve the tracking capability of modified current reference. As a result, the transient control targets of the improved LVRT control strategies can be implemented accurately. Moreover, the method is easy to implement. Finally, the proposed method is verified by the simulations on a 1.5-MW type-3 WT.