A structural safety evaluation approach of offshore wind turbine based on projection pursuit method and extension cloud model

Abstract

The offshore wind power (OWP) industry is developing towards deep sea areas, and thus the offshore wind turbine (OWT) will face more severe environmental conditions and excitations such as storms, typhoons and huge waves. The safety evaluation and early warning of OWT structures has become the key issue to ensure the stable operation of offshore wind farm (OWF) and the sustainable development of the OWP industry. In this research, one structural safety evaluation approach of OWT was proposed based on projection pursuit (PP) method and extension cloud model (ECM), and the evaluation results were discussed by considering two actual OWTs as the research objects. Firstly, the multivariate evaluation index system was established based on the safe threshold of different indexes calculated from numerical models of two OWT in the perspectives of time and frequency domain. Secondly, an index weight optimization method was proposed based on PP and particle swarm optimization (PSO) algorithm to accurately determine the importance of each indicator for safety evaluation. The ECM, which can leverage the advantages of normal cloud theory and extension model, was also utilized to establish a multi-level and multi-index safety evaluation method for OWT. The feasibility of the novel approach was further verified through the both randomly generated samples and typical measured data. Especially, one set of measured data, which shows the occurrence of excessive vibration for OWT, can be evaluated as a sub-healthy status. This result can effectively demonstrate the engineering applicability of the proposed method. Lastly, the influence of wind speed, rotation speed and power on the health status of OWT and its change rule was discussed considering the long-term monitoring data for one year. It is expected that the proposed approach can provide necessary assistance for the safe operation and intelligent maintenance of OWFs.