Low voltage ride-through of a grid-connected doubly-fed induction generator with speed sensorless vector control

Doubly-fed induction generators (DFIG) are commonly employed in medium and high power applications for variable speed drives. Grid-connected DFIG based wind turbines are subject to sudden voltage dips caused by symmetrical and asymmetrical grid faults. According to new grid codes, DFIG based wind turbines should ride-through voltage dips without interrupting their operation. Hence, they should be capable of low voltage ride-through (LVRT) to maintain stable and safe operation of power system. Furthermore, for a practical DFIG, mounting a shaft speed sensor involves high cost, maintenance, and cabling issues. In this paper, a solution to both voltage dip and absence of a speed encoder is addressed for a 22 kW DFIG setup. A detailed mathematical modeling with sensorless vector control and protection against sudden voltage drop is studied and simulated in MATLAB/SIMULINK environment.