DISTURBANCE IMMUNE DFIG FOR WIND FARM APPLICATIONS

Abstract

Energy is one of the most important factors that continue to influence the shape of civilization since evolution of mankind to this 21st Century. The cost and availability of energy significantly impacts the quality of our life, growth of the country and the stability of our environment. In recent years there has been a global commitment to develop clean and alternative forms of energy resources. Among renewable energy resources, wind generation technology has matured considerably, as wind is fairly distributed around the globe, and the conversion is low cost. However, more penetration of wind energy into existing power networks raises concern for power system operators and regulators. The problems of wind are associated with dependence on the local environmental conditions. Variability of the wind speed causes oscillations in the output power of the wind generators, resulting in a variety of consequences within the power system and in its operation. The stable operation of the Wind Energy Conversion System (WECS) amidst variety of disturbance on the microgrid is seen as a challenging task. Unbalanced magnetization of the Doubly Fed Induction Generator (DFIG) largely affect the generation profile and could cause cascading effect eventually leading to shut down of the wind farm. Moreover, popular WECS, Induction Generators (IG) in order to generate real power consumes reactive power from the mains making the operation with relatively lower power factor (pf). In order to provide requisite immunity to the DFIG based WECS, each system should be controlled in way that only balanced currents are transacted by the WECS at near unity pf. The thesis dissertation presents Synchronous reference frame (SRF) method based current estimation of the reference currents both in positive and negative sequence for control of the stator side Voltage Source Converter (VSC)and slip frequency based load levelling by rotor side VSC (RSC). MATLAB based simulation results presented in the thesis show the efficient working of WECS control amidst distorted conditions at Point of Common Coupling (PCC).