TABLE OF CONTENTS Wind energy has matured to a level of development where it is ready to become a generally accepted utility generation technology. Wind turbine technology has undergone a dramatic transformation during the last 15 years, developing from a fringe science in the 1970s to the wind turbine of the 2000s using the latest in power electronics, aerodynamics, and mechanical drive train designs [1, 2].
Most countries have plans for increasing their share of energy produced by wind power. The increased share of wind power in the electric power system makes it necessary to have grid-friendly interfaces between the wind turbines and the grid in order to maintain power quality.
In addition, power electronics is undergoing a fast evolution, mainly due to two factors. The first one is the development of fast semiconductor switches, which are capable of switching quickly and handling high powers. The second factor is the control area, where the introduction of the computer as a real-time controller has made it possible to adapt advanced and complex control algorithms. These factors together make it possible to have cost-effective and grid-friendly converters connected to the grid [3, 4].
A horizontal-axis wind turbine is the most extensively used method for wind energy extraction. The power rating varies from a few watts to megawatts on large grid-connected wind turbines.
In relation to the position of the rotor...
