Sistema de controle para conversores modulares multiníveis utilizados em conexões HVDC de parques eólicos offshore
Batista, Roberto Carlotto
This work presents a brief history of the wind generation system in general and the detailed history of the offshore wind generation system. Current data on installed capacity, power of used wind turbines and distance from wind farms up to the coast are presented. The main advantages and challenges of offshore wind generation are presented. The topologies of offshore wind farms transmission systems that can be medium voltage with alternating current (MVAC), high voltage with alternating current (HVAC), medium voltage with direct current (MVDC) and high voltage with direct current (HVDC) are introduced. It is presented the application of each of the previous topologies, emphasizing the comparison between HVAC and HVDC, noting the limitations of HVAC and the possible advantages of HVDC as a function of the distance of the transmission system. The comparison of the technology of Line Comutated Converters (LCC) with Voltage Source Converters (VSC) is also presented. A case study of a transmission system using Modular Multilevel Converters (MMC) and a HVDC link in a offshore wind power plant is presented. The operation of the MMC is shown in detail. The conversion system consists of two converter stations, one on the offshore side linked to the wind turbines and another on the coast linked to the grid connection, both with MMC converters. The connection between the converter stations will be through an HVDC link. The methodology of control of offshore formation of the network is presented. The control for synchronization with the network on the onshore side as well as voltage control on the HVDC link is also shown at work. In addition, it is presented the methodology of energy control in the poles of the MMC in both converter stations. In order to validate the proposed models, simulation results are presented. A simulation base case is used in which power flows to the offshore side first and then the flow reverses, and finally the flow reaches the nominal value of the system. Through the simulations presented, it is verified that the proposed system responded satisfactorily.