Negative Sequence Current Control of Offshore Wind Farm Based on Diode Rectifier HVDC

Offshore wind farm (OWF) can produce more electricity power than onshore one through high and steady wind energy. However, economically it is hugely problematic. The uncontrolled diode rectifier with high voltage direct current transmission system (HVDC) can help reduce installation and management costs of OWF in the future. In order to reduce economical costs and electrical losses, diode rectifier (DR)-HVDC can be a solution. However, it cannot control voltage and frequency of OWF side power system. Thus, the back to back converters of wind turbine must play a role as power system controller together. From this points, this paper proposes dual current controller of OWF with DR-HVDC transmission in transient cases. In this case, the dual current controller has negative and positive sequence current controller. In order to verify the effectiveness of the proposed controller, simulation will be conducted for two situations. First, the OWF will operate under conventional current control method under single line ground fault. Second, the OWF will be controlled by dual current controller under same conditions with first case. The proposed method will be applied to 100 MW OWF and modular multi-level converter for transmission system.