A wind turbine electrical power generating system is provided and is configured to supply generated electrical power to a main load. The system includes a wound rotor induction generator including stator windings and a generator rotor with rotor windings. The generator rotor is configured to be mechanically coupled to a wind turbine rotor of the wind turbine to receive rotational mechanical energy. A first converter is electrically coupled to the stator windings such that in operation, AC electrical power generated by the stator windings and provided to the main load passes through the first converter. A second converter is electrically coupled to the rotor windings of the generator rotor, wherein an AC frequency of the generated AC electrical power is at least partially determined by setting or controlling currents in the rotor windings of the generator rotor by the second converter.