Robust STATCOM control for the stabilisation of fixed-speed wind turbines during low voltages

This paper presents a robust voltage control scheme for fixed-speed wind generators using a static synchronous compensator (STATCOM) controller. To enable a linear and robust control framework with structured uncertainty, the overall system is represented by a linear part plus a nonlinear part that covers an operating range of interest required to ensure stability during severe low voltages. The proposed methodology is flexible and readily applicable to larger wind farms of different configurations. The performance of the control strategy is demonstrated on a two area test system. Large disturbance simulations demonstrate that the proposed controller enhances voltage stability as well as transient stability of induction generators during low voltage ride through (LVRT) transients and thus enhances the LVRT capability. ► This paper presents a control method for a STATCOM for regulating reactive power exchanged between the machine and the grid. ► The proposed method can be used to design a linear robust controller to accommodate post-fault low-voltage conditions. ► The overall system is represented by a linear part plus a nonlinear part that covers an operating range of interest required to ensure stability. ► The reactive power control allows getting a unitary power factor between the stator and the grid. ► The STATCOM control scheme is based on the reformulation of the nonlinear dynamics using the mean-value theorem.