Control system and design and transient analysis of a grid integrated wind turbine

Abstract

Wind power is one of the most reliable and developed renewable energy source. The share of wind power with respect to total installed power capacity is increasing worldwide. It is now more significant that the researchers focus more on technical improvements of wind energy conversion system. A variable speed wind turbine typically uses a maximum power tracking algorithm in order to optimize energy acquisition from wind. Although many algorithms has been introduced by the researchers in the past, to enhance the power extraction capability but they all fall short when it comes to computational simplicity and convergence time. In this thesis, a new maximum power point tracking algorithm for wind energy conversion systems has been proposed to get rid of these problems. The algorithm is based on the optimum relationship between active power and dc link voltage. The dc power is calculated from voltage and current, which are read by the algorithm. The conventional perturbation approach has been modified by introducing a new perturbing parameter to reduce computational time and system complexity. The proposed system also include a Fuzzy- PI pitch angle controller in order to analyze the output power characteristic of wind generator from cut-in wind speed to rated wind speed. A detail electromechanical model of a wind turbine with variable speed and variable pitch control is developed in Matlab/Simulink environment in order to analyze the performance of the proposed control system. The proposed model is also compared with conventional system and the comparison results show that the proposed system increases power absorption by five to seven percent. This research also investigates the transient stability of the hybrid power system with increased penetration level of wind turbine in order to find out the fault current behaviour of a grid integrated wind generator. With increasing penetration of wind power, the power system dominated by synchronous machines experience a change in dynamics and operational characteristics. Given this assertion, a systematic approach has been developed to analyze the impact of increased penetration on transient stability of a large power system. The primary basis of the method is to replace the induction generators with equivalent conventional round rotor synchronous wind generators. In this regard, the modes that are both detrimentally and beneficially affected by fault current have been identified. The results for transient stability analysis show that inducing synchronous wind generator increases transient stability of a system. This research work resulted in a new way to maximize energy extraction from wind. It also identifies the effect of wind generators on grid stability. Discussions of the obtained results were made and several factors were listed. These findings helped in proposing useful modifications for the system in order to enhance its performance.