Optimization of curtailment intervals of wind turbines through assessment of measured loads during start-up and shutdown events

Abstract

There is an increasing amount of curtailment of wind parks due to grid overload or negative market prices. Operators need to also account for the effect of curtailment on component loads, wear, and lifetime. This paper investigates curtailment leading to turbine shutdown. A novel methodology to optimize the length of curtailment intervals based on load neutrality is introduced. Measurement data from the structural health monitoring system of an onshore and an offshore wind turbine are used to quantify effects of curtailment on loads and wear of tower, blade, and pitch system. Shutdown and start-up events increase loads on the tower and pitch system. Blades benefit from lower edgewise loads and reduced erosion. Results show that load neutrality for the tower is reached on average after 63 min of idling for the onshore and after 200 min for the offshore wind turbine evaluated (not generalizable). An optimal curtailment strategy shall use flexible time intervals but ensure load neutrality on yearly average. This can serve as a simple and valuable guideline for wind farm operators to evaluate the criticality of curtailment times in terms of asset fatigue life. Future research shall investigate curtailment strategies that also include deration of power output.