A Wideband Subsynchronous Damping Controller Based on Quadratic Index for PMSG Wind Farm Connected to Weak AC System

With the increase of wind capacity, the interaction between wind turbine controller and weak AC system easily leads to sub-synchronous oscillation, and the oscillation frequency presents the characteristics of time-varying, diverse and wideband, which poses a greater challenge to the stable operation of power system than before. Based on the linear quadratic index, a wideband suppression method for subsynchronous oscillation of wind turbines is proposed in this paper. The outputs of the suppressor are added to the instruction value of the controller as supplementary control signals, which only respond to the signals in the sub-synchronous oscillation frequency band. Based on the deduced small signal model of permanent magnet synchronous generator, according to the principle of observability and participation factor analysis, some state variables are selected as input variables, and the linear quadratic index of input and output variables is taken as performance index to design a reduced-order sub-synchronous oscillation wideband suppressor. Time domain simulation shows that the controller can suppress the wideband oscillation caused by different factors in the actual wind farm without affecting the normal operation of the wind farm.