Modular multilevel converter based HVDC transmission system for offshore wind farms

Abstract

This doctoral thesis falls within the scope of electronic power converters oriented to high voltage transmission applications, in particular the power generated in remote offshore wind farms by means of HVDC subsea cables. This research is focused on the Modular Multilevel Converter (MMC) with two level submodules but also with multilevel topology submodules such as 3L-FC (three level flying capacitors) and 3L-NPC (three level neutral point capacitors). The main contribution of this thesis is the developed PWM based modulation strategy which allows the balancing of the total amount of submodules capacitors. It is applicable to the aforementioned submodule topologies under different working conditions as evidenced by experimental results.