ECN publication
Condition based control
Published by: Publication date:
ECN Wind Energy 18-10-2017
ECN report number: Document type:
ECN-E--17-047 ECN publication
Number of pages: Full text:
55 Download PDF  

Offshore wind farms are expensive to maintain and it is difficult to achieve a similar availability to onshore farms. This report examines the possible benefit of condition based control, where the controller is adapted to modify the loading of parts depending on their condition. This benefit is only examined in terms of annual electricity production. Other, secondary benefits may be possible, but are not considered. Literature indicates that the most relevant parts are the drive train, the blades and the pitch systems. Literature does not give a clear relation between loading and remaining life time of the components, so it is assumed that the remaining life time is inversely related to the loading of the parts. An Operations & Maintenance (O&M) case study into the maximum possible benefit of the condition based maintenance (CBM) and condition based control shows that an Annual Energy Production (AEP) increase of up to 2% can be achieved. For the considered reference wind farm (consisting of 120 3MW wind turbines), this boils down to 72 M€ over the lifetime of the farm. However, this figure represents an upper limit on the achievable benefit as it is based on an ideal scenario. More specifically, it is computed by assuming that, (a), CBM is applied to all turbine components, and (b), that the condition signal is always received enough time in advance of the actual failure to allow for performing the O&M planning and waiting activities before the actual failure occurs. The calculation of a more accurate estimate of the achievable benefit requires more detailed data on the failure prediction capabilities of the condition monitoring systems, which was not available in this study. However, if for example CBM is applied to only 50% of the cases, and if the assumed percentage of the logistics/waiting time that the turbine remains in operation is reduced from 100% to 30%, the lifetime revenue increase would drop down to the more realistic value of 10.8 M€. With respect to condition based control, two methods have been investigated: power downregulation and a novel pitch reduction control. Both methods deliver fatigue load reductions at the expense of some power loss, but are complementary as they target different components. In terms of economic benefits, significant revenue improvements are estimated for condition based control, ranging from 1.5-1.7 M€ (for the gearbox and the yaw mechanism) to 2.7 M€ (for the pitch system). These benefits come on top of the benefit from CBM, mentioned above.

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