Coordinated design of fuzzy-based speed controller and auxiliary controllers in a variable speed wind turbine to enhance frequency control

This paper proposes novel controllers for doubly fed induction generator (DFIG)-based wind turbines. These controllers not only optimize the transient behaviour of DFIGs, but also realize their participation in the power system frequency control task. The proposed controllers include one main speed controller as well as two auxiliary controllers. The main speed controller is a fuzzy-based controller which their parameters are optimized using the genetic algorithm (GA) to achieve the optimal transient response. It applies the rotational speed signal and causes the DFIG to return to the maximum power point (MPP) quickly after any turbulent in the wind speed. Moreover, two smart auxiliary controllers, i.e., frequency deviation and wind speed oscillations controllers are suggested. The frequency deviation controller enables the DFIG frequency support and the wind speed oscillations controller alleviates the impacts of wind speed fluctuations on the wind turbine output power both with utilizing the wind turbine kinetic energy. To investigate the efficiency of main controller, two case studies are considered. Moreover, some time domain simulations are performed on IEEE 39-bus system to evaluate the influences of the auxiliary controllers on the load frequency control task. Results confirm the effectiveness and superiority of the proposed controllers.