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???????

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