Modeling and Control Strategies for DFIG in Wind Turbines: A Comparative Analysis of SPWM, THIPWM, and SVPWM Techniques

Abstract

The paper presents a comprehensive study on modeling a doubly fed induction generator (DFIG) and explores various control strategies for pulse-width modulation (PWM) in back-to-back (B2B) converter techniques. A DFIG is characterized by a wound rotor and three slip-ring induction machines, with the stator winding directly connected to the power grid and the wound rotor interfaced with the grid through a 3-phase AC/DC/AC converter. Typically, the converter connected to the grid is referred to as the grid side converter (GSC), while the converter attached to the rotor's slip-ring circuit is termed the rotor side converter (RSC). This research delineates various PWM-based B2B converter methodologies applied to the DFIG within wind energy turbines, aiming to regulate the RSC for optimal power capture. The study employs MATLAB/SIMULINK for constructing a multi-phase voltage source converter two-level (VSC-2L) model, leveraging different PWM techniques including Sine-PWM, Sinusoidal-PWM with third harmonic injection (THIPWM), and space vector PWM (SVPWM). These techniques are assessed based on total harmonic distortion (THD) using fast Fourier transform (FFT) analysis. The findings indicate that SVPWM offers several advantages, such as ease of digital implementation, lower THD, reduced switching frequency losses, and more efficient utilization of the DC link voltage, thereby enhancing control strategy effectiveness.