Detailed Dynamic Modeling, Control, and Analysis of a Grid-Connected Variable Speed SCIG Wind Energy Conversion System

Wind energy as a renewable energy source continues to be a better alternative to fossil-fuel based generation due to its low cost and environmental benefits. While considerable research efforts have been focused on modeling and control of grid connected variable speed squirrel cage induction generator (SCIG) wind energy conversion systems (WECS), comprehensive models for grid integration studies have been almost non-existent. This paper presents the detail modeling, control and analysis of a grid-connected 2.25-MW variable speed SCIG based WECS that can be utilized for grid integration studies. The presented WECS model consists of a pitch regulated wind turbine connected to a SCIG through a gear box. Then, a full-capacity power electronic converter with maximum power point tracking (MPPT), dc bus voltage regulation and power factor correction, connects the SCIG to the grid. The power converter system comprises of back to back two-level voltage source converters linked through a dc-link capacitor. The generator and grid-side converters are controlled using indirect rotor field-oriented control (IR-FOC) and voltage-oriented control (VOC) respectively. The overall system is simulated in MATLAB/Simulink for a varying wind speed. Results show that the presented model is adequate and efficient in the representation of a variable speed SCIG WECS. In addition, the model meets all of the system performance objectives while simultaneously meeting all of the control objectives.