The invention describes a power supply arrangement (5) realised to provide auxiliary power to a wind farm (1) that feeds into a HVDC transmission link (3), which power supply arrangement (5) comprises an auxiliary power supply (50) realised to deliver auxiliary power (P aux ) to the wind farm (1); a backfeed control means (6, 41) for initiating provision of a backfeed voltage on the HVDC link (3) during a wind farm downtime; a backfeed switch (53) realised to close a DC current path between the HVDC link (3) and the auxiliary power supply (50); and a power conversion means (54, 51, T5) for converting the backfeed voltage into auxiliary power (P aux ). The invention also describes a wind farm (1) arranged to feed into a HVDC transmission link (3), comprising such a power supply arrangement (5) for providing auxiliary power (P aux ) to the wind farm (1) during a wind farm downtime. The invention also describes a method of providing auxiliary power (P backfeed ) to a wind farm (1) during a wind farm downtime.