Control of a Wind Driven Doubly Fed Induction Generator During Grid Faults

Master's Thesis from the year 2013 in the subject Engineering - Power Engineering, grade: none, , course: Electrical engineering (Renewable energy), language: English, abstract: Wind electrical power systems are recently getting lot of attention, because they are cost competitive, environmental clean and safe renewable power source, as compared with fossil fuel and nuclear power generation. A special type of induction generator, called a doubly fed induction generator (DFIG), is used extensively for high-power wind applications. They are used more and more in wind turbine applications due to ease controllability, high energy efficiency and improved power quality. This thesis aims to develop a method of a field orientation scheme for control both the active and reactive powers of a DFIG driven by a wind turbine.The proposed control system consists of a wind turbine that drives a DFIG connected to the utility grid through AC-DC-AC link. The main control objective is to regulate the dc link voltage for operation at maximum available wind power.This is achieved by controlling the and axes components of voltages and currents for both rotor side and line side converters using PI controllers. The complete dynamic model of the proposed system is described in detail. Computer simulations have been carried out in order to validate the effectiveness of the proposed system during the variation of wind speed. The results prove that , better overall performances are achieved, quick recover from wind speed disturbances in addition to good tracking ability. Generally, any abnormalities associated with grid asymmetrical faults are going to affect the system performance considerably. During grid faults, unbalanced currents cause negative effects like overheating problems and mechanical stress due to high torque pulsations that can damage the rotor shaft, gearbox or blade assembly. Therefore, the dynamic model of the DFIG, driven by a wind turbine during grid faults has been analyzed