With growing concerns over environmental pollution and globe warming, renewable energy has received considerable attention as an alternative... Show moreWith growing concerns over environmental pollution and globe warming, renewable energy has received considerable attention as an alternative energy resource of electricity production. Because of the immense potential of wind energy on the earth, wind power generation has gained significant popularity over recent years. From this research, it has been concluded that there is a constant need to reduce the size and rating of power electronic converters, improve efficiency of the electromechanical system and make the system more reliable by eliminating the gearbox. This thesis analyzes a doubly fed induction generator (DFIG) drive system for distributed wind generation systems. The structure of a doubly fed induction generator is similar to that of an induction generator. To illustrate the operation principle and control strategy of a DFIG clearly, the fundamentals and control principle of an induction generator have been discussed. For DFIG control, two closed control loops are designed-active power control loop and rotor speed control loop; and they can be switched between each other. By utilizing active power control loop, the output power of the system can be regulated to meet different customer requirements and their dependence on grid electricity can be eliminated, therefore the cost and the power loss on transmission lines can be reduced. On the other hand, by switching to the speed control loop, the system can extract maximum power at different wind speeds, and any extra power can either be stored or sold to the utility for profit. To validate the proposed concept, Finite Element Analysis (FEA) models of a doubly fed induction generator and an induction generator have been built and simulated using the software Magnet®; furthermore, the control systems of these two generators are implemented and simulated in a Matlab/Simulink environment. Finally, a Magnet and Matlab/Simulink co-simulation has been performed for the DFIG. By analyzing the simulation results, the differences between the doubly-fed induction generator and an induction generator have been demonstrated. M.S. in Electrical Engineering, May 2012 Show less
