높이에 따른 풍향 변화, 즉, 윈드비어가 풍력발전기의 출력성능에 미치는 영향을 알아보기 위하여, 본 연구에서는 제주도 북동쪽에 위치한 풍력발전단지의　2MW 풍력발전기　나셀　위에 설치된 나셀라이다로 바람조건을 측정하였다. 풍력발전기의 출력을 SCADA　시스템에서　취득하였다.　나셀라이다 측정값의 정확도 검토는 나셀라이다와 기상탑의 허브높이　풍속을 비교하여 수행되었다. 윈드비어 발생 빈도와 허브높이에서의 바람　장미를 분석하였다. 윈드비어는　풍향이 높이에 따라 시계방항으로 변동하는　비어링윈드　조건，풍향이　높이에　따라　반시계방향으로　변동하는　백킹윈드　조건　그리고　높이에　따라　풍향　변동이　거의　없는　노비어의 3가지　조건으로　구분하였다.　이　조건을　적용하여 풍력발전기의 출력곡선을　산출하고 서로 비교되었다. 또한 노비어　조건을　기준으로　비어링윈드과　백킹윈드의　연간에너지발전량의 상대오차를 산출하여　비교　분석하였다.　그 결과, 비어링윈드　조건에서　연간에너지발전량의 상대오차 값은 0.9%에서 4.5% 사이로 분석되었으며,　이는　풍력발전기의 출력이　증가함을 보여 준다. 반면 백킹윈드 조건의 상대오차 값은 -0.4%에서 -0.2% 사이로 풍력발전기의 출력이 감소함을 보였다.

In order to find out the effect of the wind direction shift with height, wind veer, on wind turbine power performance, wind conditions using a nacelle lidar installed on a 2 MW wind turbine were measured at a wind farm located on the northeastern part of Jeju Island. The power outputs were collected from SCADA system of the turbine. The accuracy of the nacelle lidar measurements was checked by comparing the wind speeds from the nacelle lidar with those from a nearby met mast. Wind veer frequencies and wind rose at the hub height of the turbine were analyzed. The wind veer types were divided into three: veering wind which is clockwise wind direction change with height, backing wind meaning counterclockwise and no veer wind that is little wind direction change with height. The power curves were derived from dataset of the three types of wind veer, which were compared one another. Also, the relative error of annual energy production (AEP) was analyzed for veering and backing conditions using no veer condition as a reference. The findings revealed that the relative errors of the veering wind condition ranged between 0.9% and 4.5% which led to overperformance of the wind turbine, while backing wind condition had relative errors ranged from -0.4% to -0.2% which resulted in underperformance of the wind turbine.