Control and Fault Handling in a Modular Series-Connected Converter for a Transformerless 100 kV Low-Weight Offshore Wind Turbine

A transformerless wind power generator concept with the potential to achieve 100 kV dc output is proposed in this paper. In this paper, the modular ac/dc converter system suitable for such a high-voltage generator is analyzed for normal operation and fault-tolerant modes. The control synthesis is addressed, based on an assumption that the control can be designed modularly. Additionally, the investigated control system can facilitate fault-tolerant operation without changing the main structure. The robustness of the module control system is analyzed, and the limits for fault-tolerant operation are investigated. The theoretical studies are supported by transient analysis through simulations of the turbine in EMTDC/PSCAD. Finally, the generator/converter solution is verified experimentally. The laboratory results were obtained using a 45 kW prototype with three generator segments and three converter units in series.