Banca de DEFESA: Jonas Pereira Falcão

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Jonas Pereira Falcão
DATE: 15/07/2022
TIME: 14:00
LOCAL: SALA INTERAÇÃO DO CDT – UNIVERSIDADE DE BRASÍLIA
TITLE:

Passive control by inverted pendulum of a floating offshore wind turbine.

KEY WORDS:

Floating offshore wind turbine; Passive control; Inverted pendulum; Vibrations.

PAGES: 301
BIG AREA: Engenharias
AREA: Engenharia Civil
SUMMARY:

The growing demand for electricity as a need for sustainable development has made many countries look for renewable sources of energy as well as a replacement for energy from fossil and nuclear fuels. In this context, design, construction and dissemination of wind turbines have become more relevant, which use devices to convert the kinetic energy of the winds into electrical energy. Wind turbines are flexible structures subjected to dynamic actions of winds and sea waves and may suffer undesirable vibrations that affect their safety and operability. The types of control that can reduce these vibrations are classified into passive, active, semi-active and hybrid. An example of passive control is an inverted pendulum which dissipates the mechanical energy of the main system, when correctly tuned to the structure, since it vibrates in phase difference in relation to the main system. The work proposes to couple an inverted pendulum to the tower of a floating offshore wind turbine to reduce the rotation vibrations of the tower when the wind turbine is subjected to the dynamic actions of winds and sea waves. Five parameters from inverted pendulum are optimized through Frequency-Response Function, considering two criterions: tower peak rotation and tower variance rotation. Once an optimal inverted pendulum configuration is defined, the Monte Carlo method is used to evaluate the random actions in the time domain and Davenport spectrum and Pierson-Moskowitz spectrum are used to evaluate, respectively, the randomness of the wind and waves in the frequency domain. The vibration reductions in the tower rotation through the deterministic analysis were around 90% for both actions. When subjected to the random action of the wind, the reductions in the maximum peak of the tower rotation were 65% in the time domain and 70% in the frequency domain. The vibration reductions in probabilistic analyses are smaller than in deterministic analyses because the spectrum energy is not concentrated in only one frequency, but distributed over a frequency range. Nevertheless, the relative error between the random responses obtained in the time domain and in the frequency domain is less than 10%. When the wind turbine is subjected to the random actions of the sea waves, the reductions in the tower vibrations are insignificant. This happens because the highest concentration of energy in the Pierson-Moskowitz spectrum occurs at a frequency far from the fundamental frequency of the structure. Besides that, the relative error between the responses obtained in the time domain and in the frequency domain is small. In this way, it was verified that it is possible to optimize the inverted pendulum parameters from a deterministic analysis and achieve significant reductions in tower vibration when the wind turbine is subjected to random excitations. 

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