الفهرس 
English abstractsOnly 14 pages are availabe for public view
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Abstract
Wind power has become the fastest growing technology for electrical power generation in the world where the share of electrical power generation from wind energy with respect to total installed power capacity is increasing worldwide. However, for efficient planning and implementation of a wind farm project, some important issues should be considered. This thesis investigates the main issues and challenges that are found when come to a decision to install a grid connected wind farm. The first issue that should be considered in the planning stage of a wind farm project is identifying the most fitting wind turbine for wind regime from available wind turbines in the market. Wind resource characteristics are varying from site to other also, wind turbine performance and its annual energy production are depending on wind resource characteristics. Therefore choosing the best suitable wind turbine for wind regime will increase the economic competitiveness of wind energy projects. In the first part of this thesis, improved turbine site matching index (TSMI) is presented to identify the most fitting wind turbine for wind regime. This index combines technical and economical evaluation for wind turbine and can make a judicious choice of the wind turbine that yields higher energy production at higher economic efficiency. The second issue that should be involved in wind energy project development is the operational challenges of wind turbines with grid which is investigated in second part of the thesis. In the second part of this thesis, operational challenges of the two major types of wind turbines, fixed speed wind turbine (FSWT) based squirrel cage induction generator (SCIG) and variable speed wind turbine based doubly fed induction generator (DFIG) with the grid are analyzed and investigated. One of the operational challenges of wind turbines with the grid is grid frequency disturbance that is caused by active power imbalances in the grid. Variable speed wind turbine based DFIG, is not very sensitive to grid frequency variation since its control system decouples the mechanical and electrical systems, thus preventing the generator from responding to grid frequency changes. But FSWT is very sensitive to grid frequency variations where there is a strong coupling between the SCIG and power system and due to the low nominal slip of SCIG, any deviations in grid frequency leads to change in rotational speed and affects the generator performance. In this thesis, impact of grid frequency disturbance on FSWT operation is analyzed. Analysis for the SCIG behavior during frequency disturbance period is carried out to predict the effect of grid frequency disturbance on the generator steady state operating point and on generator speed and on the output power of generator as well as factors that affecting operating frequency limits are analyzed. Also, simulation results are used to study SCIG behavior during the frequency disturbance. With increasing penetration of wind power generation, function of terminal voltage regulation during normal operation and enhanced fault ride through (FRT) capability during fault conditions are becoming important to maintain satisfactory performance of the power system, and it is the other operational challenge of wind turbines with power grid. For FSWT, flexible AC transmission systems (FACTS) devices, through their fast, flexible and effective control capability, provide solution to this challenge. In this thesis, three FRT schemes are proposed to enhance FRT capability of FSWT. Shunt compensation scheme that uses static synchronous series compensator (STATCOM) to generate the required reactive power during grid voltage dip, series compensation scheme that uses static synchronous series compensator (SSSC) to inject series voltage and maintain the generator terminal voltage during grid faults and a combined shunt and series compensation scheme that uses a combined approach of shunt and series grid interface topology for one voltage source converter (VSC), where the VSC in shunt interface topology works as a STATCOM to regulate terminal voltage in normal operation and in light voltage dip, and in case of serious grid voltage dip VSC instantaneously switches from shunt to series grid interface and works as SSSC to compensates the voltage and maintains stator voltage at its rated value. By this way one VSC is used to regulate the voltage in normal operation and to enhance FRT capability of the wind turbine in case of serious grid voltage dip and it is considered an advantage from the economical point of view. Concerning variable speed wind turbines based DFIG, improved control strategy for rotor side converter and grid side converter is introduced to regulate wind turbine terminal voltage fluctuations that is caused by wind speed variations and in case of grid faults, FRT scheme based series voltage compensation utilizing FACTS devices is proposed to enable the wind turbine to ride through the grid faults and remain connected to the grid without any effects on the rotor converter.