الفهرس 
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Abstract
This thesies classifies three types of protections for the DFIG :the conventional crowbar protection the series crowbar protection and a new proposed crowbar protection the thesis illustrates the dynamic behavior of the DFIGs under different studies.Enhancement protection and operation of the doubly fed induction generator (DFIG)
during the grid fault are investigated in this thesisWind power growth with a 20% annual rate has been experienced the fastest growth
among all renewable energy sources since five years ago. It is predicted that by 2020
up to 12% of the world’s electricity will have been supplied by wind power so Wind
generation is becoming the most development. During 2011, 40 GW of wind
generation capacity was added to power networks around the world. Worldwide wind
capacity has reached 254 GW, by the end of June 2012, 273 GW expected for full
year, indicating a 25% annual average growth rate in wind energy capacity.DFIG has
recently received much attention as one of preferred technology for wind power
generation. Compared to a full rated converter system, the use of DFIG in a wind
turbine offers many advantages, such as reduction of inverter cost, the potential to
control torque and a slight increase in efficiency of wind energy extraction.The DFIG
is very sensitive to any grid disturbances, if a severe voltage dip occurred due to grid
fault, high currents will pass through stator and rotor windings and also a very high
DC voltage would be induced in converter circuit, it may lead to damage the
converter circuit and the DFIG windings. Protection systems are essential to avoid the
disconnection of the DFIGs from the network during fault.This thesis classifies three types of protections for the DFIG: the conventional
crowbar protection, the series crowbar protection and a new proposed crowbar
protection (the outer crowbar protection). This thesis illustrates the dynamic behavior
of the DFIGs under different studies:
Without protection With conventional crowbar protection
With series crowbar protection
With outer crowbar protection
This thesis produces strategy of determining the suitable protection method for the
doubly fed induction generators to be applied during the grid fault.In the last decade the renewable energy sources, especially wind generation, have
gained significant interest throughout the world due to the phasing out of conventional
electrical power generation, this is caused by the global goals for the reduction of
greenhouse gas emissions [1].Wind is a form of solar energy, winds are caused by the
uneven heating of the atmosphere, the irregularities of the earth’s surface, and rotation
of the earth. Wind flow patterns are modified by the earth’s terrain, bodies of water,
and vegetation. Humans use this wind flow, or motion energy, for many purposes:
sailing and even generating electricity. The terms wind energy or wind power
describes the process by which the wind is used to generate mechanical power or
electricity. Wind turbines convert the kinetic energy in the wind into mechanical
powerTo meet the growing energy demands in the future by taking advantage of the
abundant energy in wind so as to protect the environment from CO2 released through
some of the more conventional ways of generating power. The worldwide wind
capacity reached 254 GW by the end of June 2012, out of which 16.546 GW were
added in the first six months of 2012. This increase represents 10 % less than in the
first half of 2011, when 18.405 GW were added. The global wind capacity grew by
7% within six months (2% less than the same period in 2011) and by 16.4 % on an
annual basis (mid-2012 compared with mid-2011). In comparison, the annual growth
rate in 2011 was 20. 3 %. [2], Figure 1-1 shows the expected annual and cumulative
wind installations by 2020.Wind power growth with a 20% annual rate has been experienced the fastest growth
among all renewable energy sources since five years ago. It is predicted that by 2020
up to 12% of the world’s electricity will have been supplied by wind power so Wind
generation is becoming the most development. During 2011, 40 GW of wind
generation capacity was added to power networks around the world. Worldwide wind
capacity has reached 254 GW, by the end of June 2012, 273 GW expected for full
year, indicating a 25% annual average growth rate in wind energy capacity.DFIG has
recently received much attention as one of preferred technology for wind power
generation. Compared to a full rated converter system, the use of DFIG in a wind
turbine offers many advantages, such as reduction of inverter cost, the potential to
control torque and a slight increase in efficiency of wind energy extraction.The DFIG
is very sensitive to any grid disturbances, if a severe voltage dip occurred due to grid
fault, high currents will pass through stator and rotor windings and also a very high
DC voltage would be induced in converter circuit, it may lead to damage the
converter circuit and the DFIG windings. Protection systems are essential to avoid the
disconnection of the DFIGs from the network during fault.