Controle direto da tensão de rotor de um gerador de indução duplamente alimentado por meio de um processo de otimização restrito em tempo real

Abstract

Global changes in search of sustainability are important factors for the evolution of the use of renewable energy sources. The development of research that proposes different technologies to improve the efficiency and quality of the energy generated by wind turbines is increasingly encouraged, due to its increasing participation in the energy matrices of many countries. Updating the grid codes becomes necessary, so that they adapt to the unpredictability of generation through this type of energy source. The wind energy conversion systems that use the Doubly Fed Induction Generator (DFIG) have advantages such as reduced mechanical load, simpler picth control, wide active and reactive power control and smaller power converters, which put it ahead of other wind turbine topologies. This Thesis aims to present and demonstrate the feasibility of using a new approach on voltage, active and reactive power and power factor controls through direct control of the voltage applied to the DFIG rotor, by the rotor side converter. A system of equations derived from the equivalent circuit is adopted to represent the desired operating point of the generator, and the solution of this system defines the values of the rotor supply voltage coordinates, in steady state. A new control strategy is proposed to reach the rotor voltage reference values, without violating the limits existing in other variables. This strategy is defined so that the speed of evolution of the voltage applied to the rotor is governed by the dynamic evolution of the mechanical speed of the rotor, solving an restricted optimization process in real time. The optimization process was formulated to minimize the time of convergence of the rotor speed, restricting transitory variations in the net power generated, in order to accelerate the machine without exceeding the rated current limits. Angular velocity, rotor currents and magnetizing inductance are estimated in real time. In addition, a method for defining the pitch angle and the reference rotor speed is proposed, using the Newton-Raphson numerical solution method.