Structural Response of a Commercial Wind Turbine to Various Stopping Events

Abstract

Increases in forced curtailments at commercial wind farms have triggered a need to investigate turbine behaviour during stopping events. A 2.3 MW commercial horizontal axis wind turbine instrumented with a fiber Bragg grating strain array was subjected to the three most common types of stopping sequences performed by the turbine to measure the supporting tower's structural response. An overview of each considered stop type is included identifying their individual mechanical processes as well as their specific triggers. The along-wind and transverse strain measurements at varying elevations of the tower are presented and discussed. Distinguishable response characteristics for each stop type are identified at stop initiation, during rotor deceleration, and following event completion. Results obtained are subsequently compared to the tower strain reactions as a result of typical power production as well as pure yawing of the nacelle. Furthermore, the strain signal has been subjected to a discrete wavelet transform identifying variations in the signal frequency content, triggered by the stopping events.