Energisation Method for Offshore Wind Farms Connected to HVdc via Diode Rectifiers

Diode rectifiers (DRs) have been recently suggested as a viable alternative for connecting offshore wind farms (OWFs) to HVdc, eliciting growing interest from both industry and academia. However, energisation of DR-connected OWFs is not straightforward. The present study constitutes a proof of concept of a novel energisation method for DR-connected OWFs, in which auxiliary power is provided from the shore through the HVdc link and the dc bus bar of one or more WTs. The proposed method provides an alternative with minimal additional hardware, which can be easily extended to more WTs in the OWF, increasing reliability by providing redundancy. The study includes coinciding auxiliary loads with active and reactive power components and a semi-aggregated OWF model, in which every WT is individually represented in the string containing the energising WT. Two additional sequences of simulation events are considered following the initial energisation sequence. Such sequences comprise wind power taking over the provision of the auxiliary power and the run-up to maximum (available) power production. The simulation results indicate that the proposed method is a suitable alternative for energising OWFs connected to HVdc via DRs.

The manuscript has been submitted to IEEE Transactions on Power Delivery.