Modeling and Control of Dual Converters on a Grid Connected Wind Power Energy Conversion System with Doubly-Fed Induction Generator in the Case of Adama II Wind Farm

Abstract

The demand of energy is drastically increasing now days mainly in developing countries like Ethiopia. It is global and increasing demand in developed countries. The penetration of wind energy generation in to existing power system network is increasing rapidly during recent years. But Ethiopia electric power corporation is using wind power to solve electric power shortage in the existing grid. Currently 153MW from Adama II wind farm, 120MW from Ashegoda wind farm and 51MW from Adama I wind farm of the country’s power is generated from wind power. The number of Doubly- Fed Induction Generator has grown over the last few years in several countries. In Ethiopia, among the most commonly used generators Adama II wind farm use Doubly-Fed Induction Generator nowadays. Its stator is directly connected to the grid, whereas the rotor is tied via dual (back-to-back) converters. Doubly fed induction generator connected to a grid through back-to-back converter have problems, such as converter control, and power quality. Therefore, improving the reliability of the wind turbine system in power generation sector with optimal performances is one of the important tasks. A detail study of the performance of wind turbine systems in various case scenarios namely, using different pulse width modulation types namely, sinusoidal pulse width modulation (SPWM), third harmonics injection pulse width modulation (THIPWM), space vector pulse width modulation (SVPWM) and using different converter topologies are investigated. This thesis is mainly focused on backto back converter modeling and pulse width modulation techniques comparison in order to reduce voltage and current harmonic distortion and control real and reactive power. From the comparative study the DFIG based wind turbine system studied in this thesis, using either twolevel converter or three-level NPC converter using SVM achieve the IEEE 519 criteria of THD which is less than 5%. Analysis and modeling have been developed using MATLAB/SIMULINK software based on data obtain from Ethiopian Electric Power (EEP) and Adama II wind farm site.