Indirect Speed Control Strategy for Maximum Power Point Tracking of the Dfig Wind Turbine System

In this article, a control strategy for Maximum Power Point Tracking (MPPT) of a wind turbinesystem based on a Doubly Fed Induction Generator (DFIG) is presented. The proposed strategy consists of the Indirect Speed Control (ISC) taking the Low Speed Shaft (LSS) as variable input. Even though the pitch control mainly influences the power extraction, this implementation allows the MPPT to optimize the Power Coefficient (Cp) in terms of dynamic response. The controller has been designed in order to allow the wind turbine to reach the MPPT along the partial load operation. For these experiments, a 1.5 MW wind turbine was modeled and simulated by using Matlab and Fatigue, Aerodynamic, Structure and Turbulence (FAST) software. In order topresent the achieved results, a comparison between the ISC and a classical PI controller is made. The Cp curves as well as the output power display an important improvement in terms of stability. These results are possible because the appropriate values of optimal Tip Speed Ratio (TSR) and maximum Cp have been properly established.