Sistema eólico baseado em DFIG com capacidade LVRT e suporte de tensão

Abstract

The climate issue has been a concern for world leaders as the years go by, and the fact that most of the electricity produced worldwide comes from fossil fuels creates a huge demand for investment in electricity generation based on Renewable Energy Sources RES. In this context, wind generation has been gaining prominence worldwide, including in Brazil, whose installed wind generation capacity is currently among the ten largest in the world. Statistically, areas with high potential for using wind resources are spread throughout countries’ territories, so wind energy is introduced into the electricity grid through Distributed Generation Systems SGDs. With the significant increase in the penetration of wind generation in the electrical systems of countries, it became essential to create operating standards for this type of SGD. Therefore, electricity regulatory agencies worldwide have instituted specific grid codes for connecting wind generation to the grid. One of the main points addressed in the countries’ grid codes refers to the SGDs ability to remain connected in cases of variation in the grid voltage in a steady state, called Low-Voltage Ride-Through LVRT capacity. Each country has in its grid code an LVRT curve that determines how long the SGD can remain connected to the grid for each voltage deviation range, about the nominal operating voltage. In this work, an SGD based on wind generation with LVRT capability is designed. The topology of the proposed SGD consists of a Double Feed Induction Generator DFIG generator connected to the PAC via stator. The rotor is connected to the PAC via a back-to-back converter. The back-to-back controls of the DFIG rotor phase currents, which, due to the magnetic coupling between the stator and rotor windings, control the active and reactive powers supplied to the PAC via the stator. In cases of undervoltage, the LVRT control block controls the injection of reactive power into the grid, increasing the voltage at the PAC. In cases of overvoltages, the consumption of reactive power from the grid is controlled, resulting in a decrease in the voltage at the PAC. In a scenario of higher overvoltage, where the reactive power consumption is not sufficient to cause the PAC voltage to decrease to operational levels, the LVRT control block also controls the reduction of the active power injected into the grid, forcing the PAC voltage to reduce a little further. In circumstances where the LVRT is unable to revert the PAC voltage to operational levels, the SGD is equipped with a Breaking Chopper; this device promotes the disconnection of the SGD in cases of non-reversal of the electrical surge, dissipating the active power produced in the wind turbine through its resistive branch. At the end of the project, simulation results are presented with operational situations of the SGD and the LVRT block to analyze the system behavior.