A LOOK-AHEAD ADAPTIVE CONTROL SYSTEM FOR WIND TURBINE GENERATORS

EXISTING CONTROL SYSTEMS FOR PITCH-CONTROLLED WIND TURBINES STABILIZE ROTOR POWER BY ADJUSTING BLADE PITCH IN RESPONSE TO OVER-OR-UNDER POWER CONDITIONS IN A FEEDBACK LOOP. THE PITCH CONTROL MECHANISM LAGS BEHIND THE ROTOR POWER VARIATIONS THAT ARE BEING CONTROLLED. THE TIME LAG CAUSES POWER OUTPUT FLUCTUATIONS THAT NECESSITATE OVER-DIMENSIONING OF ROTOR, TRANSMISSION, AND GENERATORS TO OBTAIN A SATISFACTORY SERVICE LIFE. ALSO, IT CAUSES FREQUENT START8STOP CYCLES WHEN THE WIND SPEED FLUCTUATES ABOUT THE CUT-IN POINT. AN INNOVATIVE LOOK-AHEAD ACOUSTIC WIND SPEED AND TURBULENCE SENSOR WILL BE USED TO ELIMINATE THE TIME LAG. THE ADAPTIVE CONTROL SYSTEM WILL PITCH THE ROTOR BLADES IN ANTICIPATION OF A GUST (FEED-FORWARD), RATHER THAN AFTER ITS ARRIVAL. THE RESULTANT MORE STABLE ROTOR POWER REMOVES THE NEED FOR DOWN RATING OF THE EQUIPMENT LEADING TO GREATER ENERGY CAPTURE AND FEWER START-STOP CYCLES. FEED-FORWARD CONTROL IS INHERENTLY STABLE. THIS FEATURE IS CRUCIAL, BECAUSE IT DRASTICALLY REDUCES THE DIFFICULTY OF IMPLEMENTING EXPERT SYSTEMS FOR ADAPTIVE CONTROL. THE ADAPTIVE CONTROLLER ITSELF, IS DESIGNED TO INFLUENCE BLADE PITCH WITHOUT BECOMING PART OF THE STABILITY-SENSITIVE PITCH CONTROL FEED-BACK LOOP. THUS, THE LOOK-AHEAD ADAPTIVE CONTROL SYSTEM (LACS) CAN BE RETROFITTED TO EXISTING MACHINES, WITHOUT AFFECTING THEIR EXISTING CONTROL SYSTEMS. PHASE I IS DEDICATED TO PROOF OF CONCEPT TESTING. CONTROL ALGORITHMS ARE DEVELOPED USING COMPUTER SIMULATION. THEY ARE TESTED BY USING AN EXISTING ACOUSTIC WIND SENSOR FACING UPWIND FROM THE FOOT OF THE TOWER OF THE WIND TURBINE USED FOR TESTING. IN PHASE II, THE SYSTEM WILL BE DEVELOPED INTO A COMPACT UNIT FOR COMMERCIAL INSTALLATION ON THE HUB OF WIND TURBINES.