There are mainly two types of wind generating systems:
fixed speed type and variable speed type [5]. In a fixed speed
wind generating system, an ordinary squirrel-cage induction
machine is used as a generator. The generator is directly
connected to a network through a transformer. In a variable
speed wind generating system, either a doubly-fed induction
generator with a reduced size power converters or a permanent
magnet synchronous generator with a full-size power
converter is used. Most of the large size modern wind farms
use variable speed wind generators. However, fixed speed
wind generators are usually used for low power applications
because of some advantages such as low cost, operational
simplicity, brushless construction and maintenance free
operation [6].