A Modular Series Connected Converter Structure Suitable For A High-Voltage Direct Current Transformerless Offshore Wind Turbine

A modular generator/converter system suitable for a 100kV transformerless HVDC offshore wind turbine is analyzed in this paper. The large diameter generator combined with mechanical tolerances may result in substantial parameter deviations. Therefore, the impact of such parameter variations is analyzed. A steady-state model relating these variations to the imbalances between module DC voltages has been developed. Additionally, the impact of different control strategies was assessed through simulations in EMTDC/PSCAD. Finally, experimental verification of the system performed on a 45kW laboratory prototype is presented. The theory is developed with the transformerless wind turbine concept in mind but is also applicable to other similar series connected converter topologies.Copyright (c) 2013 John Wiley & Sons, Ltd.