Fault tolerance of a 10 MW, 100 kV transformerless offshore wind turbine concept with a modular converter system

This paper presents the investigation of fault tolerance for a transformer-less generator/converter concept suitable for 10 MW offshore wind turbines. The fault tolerance is necessary to achieve good availability for the turbine, since the accessibility can be sparse for turbines located far offshore. Based on the identified opportunities, changes to the control of the converter and turbine are proposed to exploit the inherent fault tolerance possibilities in the converter system. The transient response to faults, bypass and continued operation of the turbine was investigated through simulations. An estimate of the availability of the turbine with and without fault tolerance is presented. The estimate indicates that the redundancy will be beneficial, despite increased cost.