Question

Advantage and disadvantage of doubly fed induction generator

Answer 1

Doubly-fed induction generator (DFIG) wind turbine (WT) is an integrated part of distributed generation system. The use of DFIG in wind farms is growing rapidly because of its advantages in decoupled active and reactive power control. However, one of the main disadvantages of DFIG is that it is very sensitive to grid faults. To analysis dynamic behaviors of DFIG during grid faults, a model including wind wheel, wind speed, drive train, generator, and converters has been proposed. This paper examines the use of distribution static compensator (D-STATCOM) as a dynamic voltage restorer at the point of common coupling (PCC) to improve the grid fault ride-through (FRT) capability and thereby protecting system stability during disturbances. The simulation results illustrate the transient responses of DFIG when a sudden short circuit at PCC is introduced. Besides, the paper also shows detailed comparisons of the transient behaviors between DFIG and conventional induction generator wind turbine under grid fault conditions

Answer 2

Explanation:

 DFIG can feed power through the stator as well as rotor to the grid.

 The stator is directly connected to the fixed frequency grid while rotor is connected via

bi-directional back-to-back converters.

 If the generator is running super-synchronously (i.e. NR speed is greater than NS speed),

the electrical power is delivered by both the rotor and the stator to the grid.

 If the generator is running sub-synchronously (i.e. NR speed is less than NS speed) the

electrical power is delivered to the rotor from the grid.

 Generated voltage is 690 V AC. So it must be step up to 33 KV to connect to power

grid.