Modeling and control of a grid_connected wind energy conversion system with doubly fed induction generator

The wind turbine with a doubly fed induction generator (DFIG) is widely used in the modern wind energy
industry. DFIG is an asynchronous generator with a wounded rotor, in which the rotor circuit can be
controlled by external devices to achieve variable speed operation. The study focused on simulation of a gridconnected wind turbine with DFIG in MATLAB for analyzing and studying the principles and operation
modes. Models (subsystems) of all electric power elements of a wind energy conversion system with DFIG
were developed using ready and newly created subsystems in MATLAB. The main operating modes (supersynchronous
and sub-synchronous modes) of a grid-connected wind turbine with DFIG were described when
the wind speed changes. The stator voltage-oriented control (SVOC) was used to control the rotor-side
converter, and voltage oriented control (VOC) was used to control the grid-side converter. In addition, pitch
angle control and DFIG synchronization to the grid were implemented in the modeling. The results of the
study showed that the given wind turbine with DFIG allows adjusting the rotational speed of the generator
from (0.67 pu) to (1,15 pu) when the slip changes from the sub-synchronous mode (+0,33) to the supersynchronous
mode (–0,15). Thus, wind energy is converted effectively.