الفهرس 
Thesis objectives and scope of the thesis work
VOLTAGE SAG AND RACTIVE POWEROnly 14 pages are availabe for public view
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Abstract
IEEE standards 446-1995 stated that the distributed generators must be disconnected during faults for maintenance and protection. But sometimes, it takes time to reconnect the renewable source and synchronize it again on the grid. It is important to remove any system faults so that the rest of the power distribution network is not interrupted or damaged. When a fault occurs somewhere in a power distribution network, the voltage is affected throughout the power system, Events are often associated with either voltage sag or voltage swell, and they may thus cause serious power interruptions. Wind turbines (WTs) should participate in grid voltage support in steady state and remain connected to the grid after fault occurrence to maintain the reliability during and after a short-term fault.
Renewable energy sources are established to help in maintaining the power generation and support consumption balance; a condition which is necessary to stabilize the functioning of the power system. Wind turbines, based on doubly fed induction generators, which are usually driven by variable speed wind turbines, are the most popular sources of renewable energy implemented and connected to power grids. Some faults may occur in the system for short time. In such cases some measures should be taken to protect both grid and wind turbines.
According to standards wind turbines must be switched off during fault. So, it is very important to analyze the power system with respect to faults and abnormal operation to prevent turbine disconnection. As a series compensator, dynamic voltage restorer(DVR), has been applied to restore the voltage level.
The DVR provides three phase controllable voltage, whose vector (magnitude and angle) add to the source voltage to restore the load voltage to pre-sag conditions. In this thesis, a dynamic voltage restorer(DVR), is applied to keep the voltage terminal of a Doubly Fed Induction Generator(DFIG), driven by the wind turbine, within an acceptable range. The DVR is tested under different loading conditions and under symmetrical and unsymmetrical faults.
A simulating model has been constructed and performed on the Matlab Simulink under different symmetrical, asymmetrical fault, and different conditions. The conclusions of the research work show that the proposed system withstand all cases of voltage dips and swell according to the grid codes efficiently.