Abstract: A wind turbine auxiliary power system configured to receive electrical power from an electrical power generating system of the wind turbine or from a power grid. The auxiliary power system includes an auxiliary transformer having a primary side configured to be coupled to the electrical power generating system of the wind turbine and a secondary side configured to be coupled to auxiliary power consumers of the wind turbine and to provide transformed electrical power to the consumers. It further includes an electronic on-load tap changer provided on the auxiliary transformer, wherein the electronic on-load tap changer includes taps on at least one transformer winding of the auxiliary transformer and semiconductor switches that are coupled to the taps and that are configured such that by controlling the semiconductor switches, the transformation ratio of the auxiliary transformer is adjustable to compensate for voltage variations on the primary side of the auxiliary transformer.