Hybrid HVDC System for Offshore Wind Farms Connection Using Series-connected Diode Rectifier Units

This paper presents a hybrid high voltage direct current (HVDC) system for offshore wind farms (OWFs) connection using a series-connection of diode rectifier units (DRUs). The proposed approach overcomes all the drawbacks of the DRU in such applications using a low-power voltage source converter (VSC) connected in parallel with all the DRUs. The distributed version of the proposal is presented as well in which a number of VSCs are connected in parallel with individual DRUs. A comparison in terms of relative losses, cost and volume is carried out between the proposed approach and the traditional VSC-HVDC connection for OWFs. The performance of the proposal is validated through a detailed switching model of the system using the operation of a modular multilevel converter with half-bridge cells.