Abstract
In recent years, the rapidly-increasing demand for energy generation from renewable resources has been noticeable. Additional requirements are consequently set on Wind Turbine (WT) systems, primarily reflected in WT size and power rating increases. With the size increase of WT, structural loads/fatigue stress on the wind turbine become larger, simultaneously leading to its accelerated aging and the shortening of its lifetime. The primary goal of this contribution is to establish an approach for structural load reduction while retaining or slightly sacrificing the power production requirements. The approach/control strategy includes knowledge about current fatigue damage and/or damage increments and consists of multi-input multi-output controllers with variable control parameters. By the appropriate selection of the designed Multi-Input Multi-Output (MIMO) controllers, the mitigation of structural loads in accordance with a predefined range of accumulated fatigue damage or damage increments, exactly to the extent required to provide a predefined service lifetime, is obtained. The validation of the aforementioned control strategy is based on the simulation results and the WT model developed by National Renewable Energy Laboratory (NREL). The obtained results prove the efficiency of the proposed control strategy with respect to the reduction of rotor blade bending moments, simultaneously exhibiting no significant impact on the resulting power generation.
Highlights
Energy generation from renewable sources has gained much attention in the last decade due to the drastic reduction of conventional energy sources from year to year and the rapid climate change primarily related to global warming
By the evaluation of fatigue loads and the appropriate adoption of the control strategy according to the examined fatigue loads, it was intended to achieve the mitigation of structural loads
Five different Multi-Input Multi-Output (MIMO) controllers corresponding to different levels of structural load reduction were designed
Summary
Energy generation from renewable sources has gained much attention in the last decade due to the drastic reduction of conventional energy sources from year to year and the rapid climate change primarily related to global warming. Structural load mitigation of WT was discussed and achieved using different approaches in the mentioned contributions, the lack of solutions that include the information about the current state-of-health of WT and precisely-defined levels of the load that needs to be mitigated to achieve the predefined service lifetime is noticeable In this contribution, the evaluation of fatigue loads, targeted at integrating the knowledge about accumulated damage in the control strategy to mitigate structural loads, is given. Contrary to the aforementioned contributions, different easy to design and implement LQR-based IPC controllers and a suitable control selection module are used to achieve integration with the online estimated state-of-health and to guarantee the predefined service lifetime. The controller parameters are changed depending on the actual degradation state of WT rotor blades
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