고정식 해상풍력발전기의 동적 하중 계산 및 응답해석에 관한 연구

Abstract

The utilization of renewable resources such as wind and solar to generate electric power has been receiving considerable attention in recent years. Wind energy in particular has been fast growing and recognized as one of most successful energy sources. Offshore wind farm has a great advantage of geographical conditions such that wind speed and quality being more favorable than those in land. The economics of the substructures are different depending on the installation depth. The substructures are divided into fixed type and floating type. Most of the current offshore wind turbine models are fixed types like a monopile and a jacket type.This study is a dynamic load calculation and response analysis of a monopole type and a jacket type offshore wind turbine through a code development. Because the offshore wind turbine system is subjected to wind and wave, current forces, it is necessary to simulate those dynamic loads included. In addition, the marine growth is also considered. The marine growth is known to give adverse effects on the performance of a offshore structure. The offshore wind turbine is subjected to more various irregular and huger loads than the onshore wind turbines and the stability of structures is supported by the piles driven deeply in the subsoil. So it is more important for the offshore structures to consider soil-pile interaction than onshore wind turbines, and for an exact analysis it should be done in soil-pile-superstructure system. Considering soil-pile-superstructure interaction, the spring stiffness between a pile and soil is evaluated by using the coefficient of subgrade reaction, the p-y curve, and the subsoil elastic modulus. Tower and substructure of fixed offshore wind turbine are modeled as multi degree of freedom (MDOF) structure. It is assumed that blades, nacelle are composed of concentrated masses. In order to obtain a dynamic response, Newmark's method is used. The 5MW NREL reference wind turbine models with a monopile type and a jacket type are used for analysis. This analysis is performed in a random offshore environment.