Abstract: Reliable load information is a key factor in evaluating the fatigue and rest life cycle, but continual load monitoring is often difficult in engineering practice. Aimed at the dynamic characteristics and load features of offshore wind turbines, this paper presents a time-domain load identification technique, based on the five points method, which can eliminate the influence of initial value, suppress the influence of error transfer, and reduce accumulative errors so as to improve its stability and robustness. First, this method is verified via application to several validation cases using the spring-mass damping model; then, it is applied to a 5 MW monopile offshore wind turbine provided by Facility for Accelerated Service Testing (FAST). The results show that the method can identify turbine operational loads accurately and stably, with its results not influenced by wind speed or operation strategy control.

Key words: offshore wind turbine, five points method, operational load identification, FAST, robustness