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DOUBLY FED INDUCTION GENERATOR FOR WIND ENERGY CONVERSION
WHAT IS A DOUBLY FED INDUCTION GENERATOR?
WOUND ROTOR INDUCTION GENERATOR
BRUSHES PROVIDED FOR ACCESS TO ROTOR WINDINGS
WHY IT IS CALLED SO?
STATOR AND ROTOR WINDINGS EXTERNALLY ACCESSABLE
CAN ACTIVELY PARTICIPATE IN ENERGY CONVERSION PROCESS
BASIC PRINCIPLE OF WIND ENERGY CONVERSION
ELECTROMAGNETIC INDUCTION WIND MAKES TURBINE ROTATE,
TURBINE ROTATES ROTOR OF GENERATOR
WHAT MAKES IT COMPLEX?
VARYING WIND SPEED CONSTANT FREQUENCY OUTPUT
REQUIRED
DFIG AS A WIND GENERATOR
THE PRINCIPLE
BY CONTROL OF ROTOR CURRENTS ACTIVE AND REACTIVE POWER FED TO GRID CAN BE ADJUSTED INDEPENDENT OF GENERATORS TURNING SPEED
CONTROL ACHIEVED THROUGH BACK TO BACK VOLTAGE SOURCE CONVERTER
SIMPLE EXPLANATION OF PRINCIPLE:- WOUND ROTOR MOTOR SPEED
CONTROLLED BY INSERTING RESISTANCE
SAME FOR GENERATOR IF ROTOR OVER
SPEEDS,RESISTANCE PLACED IN CIRCUIT ABSORBS
ENERGY WHILE STATOR FEEDS CONSTANT
50HZ TO POWER LINE
RESISTANCE REPLACED BY A CONVERTER
ABSORBING AND FEEDING POWER IN TO POWER LINE INSTEAD OF DISSIPATING IT
MORE EFFICIENCY
SOME FEATURES:- ROTOR TURNS 2 TO 3 TIMES STATOR
TURNS -LOW RATED CURRENT OF CONVERTER OPERATIONAL SPEED RANGE +/-30% OF
SYNCHRONOUS SPEED OUTSIDE RANGE -HIGHER THAN RATED ROTOR VOLTAGE -VOLTAGE TRANSIENTS DUE TO GRID
DISTURBANCES MAGNIFIED
CROWBARS -FOR PROTECTION OF
IGBTS ,DIODES OF CONVERTER -SHORT CIRCUIT ROTOR WINDINGS
THROUGH A SMALL RESISTANCE
CONTROL DESCRIPTION
q-AXIS ROTOR CURRENT (Iqr) CONTROLS STATOR ACTIVE POWER Ps
-CONTROLS FREQUENCY d-AXIS ROTOR CURRENT (Idr)
CONTROLS STATOR REACTIVE POWER Qs
-CONTROLS PF
A STATOR FLUX VECTOR CONTROL ALGORITHM TO CONTROL ROTOR CURRENT:-
DFIG MODELLING:-CLASSIC EQUATIONS
ACTIVE AND REACTIVE POWER CONTROL:-
Taking d-q reference frame synchronized with stator flux. Setting quadratic component null
neglecting stator resistance
stator active and reactive components
these relation helps in design of regulator
DFIG LOW VOLTAGE RIDE THROUGHPROBLEM
STATOR FLUX EQUATION
SUDDEN VOLTAGE DIP- FLUX STATIONARY-HIGH SLIP-HIGH ROTOR CURRENT AND VOLTAGE
CROWBAR ACTIVATED-USES THYRISTOR
GRID DISCONNECTION
CROWBAR CIRCUITS:-
SOLUTIONS FOR LVRT PROBLEM:-
ACTIVE CROWBAR:- USES IGBT
STATIC SERIES COMPENSATOR -ISOLATE WIND TURBINE
STATCOM -REACTIVE POWER COMPENSATION -NOT PROPOSED HVDC
ADVANTAGES OF DFIG OVER OTHERS
VARIABLE SPEED LESS STRESS INEXPENSIVE LOW RATED
CONVERTER RECOVER SLIP POWER-MORE
EFFICIENCY
CONCLUSION
IF THE LVRT PROBLEM IS OVERCOME DFIG IS A GOOD CHOICE AS A WIND GENERATOR BECAUSE OF ITS HIGH EFFICIENCY AND CHEEPNESS
QUESTIONS???????
THANKYOU FOR LISTENING!!!