Abstract
Recently, the importance of individual pitch control (IPC) capability in wind turbine systems has been emphasized to achieve the desired power performance and mitigate the aerodynamic imbalance load for the mechanical integrity. Compared to collective pitch control (CPC), which assigns identical pitch angles for all employed blades, IPC is capable of generating other various sets of pitch angles to manipulate the aerodynamic load. Thus, the mechanical elements of wind turbine systems may take advantages from this variation, which allows wind turbines to have lighter designs and longer lifetimes. One of the essential mechanical components in the wind turbine is a primary bearing supporting the blades–rotor–shaft unit, which has not been fully investigated yet among the structural elements in the wind turbine system. In this regard, this research focuses on predicting the bearing life span of a NACA64-A17 two-blade 5-MW wind turbine system for the domains of allowable individual pitch angles by IPC. In particular, under the effect of various wind speeds, a bearing life span was determined based on the average value of load cases—satisfying both appropriate power level and the allowable domain of pitch control angles, which were possibly conveyed by IPC—and the result was compared with the bearing life predicted based on the domain of pitch angles, as generated by the CPC strategy. Consequently, in the ranges of high wind speeds, it was found that the average applied load to the bearing is reduced under the domain of the IPC-based pitch angle, resulting in possibly increasing the life span of the bearing. With the presented results, it is hoped that this work will provide important insights for those that majorly concern designing the primary bearing of the IPC-based wind turbine system.
Highlights
With the growing importance of wind energy as an electrical power generation source, lifetime extension and the maintenance cost reduction of large-scale wind turbines are the key challenging parameters to wind industries with an emphasis on robustness and reliability enhancement
The rotor system, including the pitch control system and blades is more vulnerable than others in terms of failure rate.one of the critical mechanical components in wind turbines is a main shaft spherical roller bearing (SPB) [3,4] to support the turbine thrust and acting forces, of which failures usually require the complete removal of the drivetrain system and a land shop-based repair
individual pitch control (IPC)-based control domain is more advantageous to prolong the bearing life span than the collective pitch control (CPC)-based observed that the loads Pa .ipc are almost identical to or slightly larger than Pa.cpc for one for higher wind speed.In other words, for Vm > 12, it can be said that more various regulated pitch
Summary
With the growing importance of wind energy as an electrical power generation source, lifetime extension and the maintenance cost reduction of large-scale wind turbines are the key challenging parameters to wind industries with an emphasis on robustness and reliability enhancement. To implement the IPC control strategy in large wind turbines, a physical understanding of the blade rotor system and bearing reaction under inhomogeneous wind shear is important. This paper originally predicts the bearing life cycle of a two 5-MW NACA64-A17 blade wind turbine system under the aerodynamic imbalance induced by the combinations of allowable individual pitch angles. Many scientific investigations have discussed the load mitigation alongside a blades pitch angle regulated control system for main structural components such as the blades, hub, and tower, the influence of such control strategies for the lifetime of a primary bearing has not been fully explored yet.
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