Power Electronics for Renewable Energy Systems, Transportation and Industrial Applications

Chapter 6High Power Electronics: Key Technology for Wind Turbines

Frede Blaabjerg and Ke Ma

Department of Energy Technology, Aalborg University, Aalborg, Denmark

6.1 Introduction

To date, wind power is still the most promising renewable energy source, as reported in [1], because it has relatively low energy cost. The wind turbine system (WTS) technology started with a few tens of kilowatts of power in the 1980s, whereas nowadays, multi-megawatt (MW) wind turbines are generally installed and their size is still growing [2–5]. There is a widespread use of wind turbines in the distribution networks and more and more wind power stations are acting as traditional power plants, which are connected to the transmission networks. For example, Denmark has high wind power penetration in major areas of the country, and today, more than 30% of the country's electrical power consumption is covered by wind [6].

Initially, wind power did not have a serious impact on the power grid system. The wind turbine solution was based on a squirrel-cage induction generator (SCIG) connected directly to the grid, and thus, power pulsations in the wind were almost directly transferred into the networks. Furthermore, there was no controllability for the delivered active and reactive powers, which are important control parameters in regulating the frequency and voltage of the grid system. Nowadays, following the dramatic increase in the penetration and power level of wind turbines, wind power has a significant ...