Multi-megawatt wind turbine converter configurations suitable for off-shore applications, combining 3-L NPC PEBBs

This paper presents two power converter configurations, suitable for an off-shore wind turbine in the range of 6 MW. These, which may either drive a Permanent Magnet Generator (PMG) or an Electrically Excited Synchronous Generator (EESG), are built combining a number of water-cooled, 3.1 kV, 3-Level Neutral Point Clamped (3L-NPC) Power Electronic Building Blocks (PEBB) that are based on High Voltage IGBTs (HV-IGBT). The first configuration employs two electrically isolated conversion lines, achieved by having two independent stator windings, where the converter outputs are connected in parallel at the grid side by means of two sets of line inductors. The second configuration employs a series connection, achieved by having open-end terminal connections, both at the machine and grid-side transformer. The paper begins by describing the PEBB modules, followed by the detailed description of the proposed configurations. Subsequently, a detailed comparison considering the main features for an offshore application is presented.