Wide Frequency Range Suppression of Subsynchronous Oscillation for DFIG Wind Farm Based on Optimal Control

The subsynchronous oscillation of wind turbines is affected by many factors in the working environment and conditions and the oscillation frequency has the characteristic of broadband oscillation, which puts forward new requirements for the design of suppressing the oscillation. This paper designs a suppression method of wide frequency range for subsynchronous oscillation of doubly-fed induction generator(DFIG) wind farm based on optimal control. First, the small signal linearized model of the DFIG is established in this paper. Then based on the quadratic index in the optimal control theory, the optimal time control theory is used to determine the weight coefficient of the control variables and the state variables of the quadratic index, then the optimal feedback controller is designed. Finally the simulation shows that the feedback controller designed in this paper has a good suppression effect on the broadband subsynchronous oscillation generated by the DFIG under complicated working conditions. For a more complicated multi-machine system, the controller also has a significant suppression effect on the subsynchronous oscillation.