A method of controlling an engine-driven, electrical generator, the generator including a rotor having three-phase windings (31a - 31c) and a stator having a main winding, connected to a stator output (33a - 33c) and generating at the stator output an output voltage at a frequency with the engine running at an operating speed, the method comprising the steps of: connecting the output of the stator of the generator to a load; varying the operating speed of the engine in response to the load; and modifying the frequency of the output voltage to a predetermined level. wherein the step of modifying the frequency of the output voltage comprises the additional steps of: calculating the difference between the frequency of the output voltage and the predetermined level and providing the difference as an adjustment frequency; modifying the frequency of the output voltage by the adjustment frequency. the method comprising the steps of: operatively connecting the output of the stator (33a-33c) to an input of an inverter, the inverter receiving the output voltage at the frequency; and operatively connecting an output of the inverter to the windings of the rotor, the inverter supplying power to the rotor windings at the adjustment frequency, characterized in that: the stator has a quadrature winding shifted 90 degrees from main winding and the method comprises the step of operatively connecting the DC link of the inverter to the quadrature winding of the stator to provide the DC link with current. connecting the output of the stator of the generator to a load; varying the operating speed of the engine in response to the load; and modifying the frequency of the output voltage to a predetermined level. wherein the step of modifying the frequency of the output voltage comprises the additional steps of: calculating the difference between the frequency of the output voltage and the predetermined level and providing the difference as an adjustment frequency; modifying the frequency of the output voltage by the adjustment frequency. the method comprising the steps of: operatively connecting the output of the stator (33a-33c) to an input of an inverter, the inverter receiving the output voltage at the frequency; and operatively connecting an output of the inverter to the windings of the rotor, the inverter supplying power to the rotor windings at the adjustment frequency, characterized in that: the stator has a quadrature winding shifted 90 degrees from main winding and the method comprises the step of operatively connecting the DC link of the inverter to the quadrature winding of the stator to provide the DC link with current. calculating the difference between the frequency of the output voltage and the predetermined level and providing the difference as an adjustment frequency; modifying the frequency of the output voltage by the adjustment frequency. the method comprising the steps of: operatively connecting the output of the stator (33a-33c) to an input of an inverter, the inverter receiving the output voltage at the frequency; and operatively connecting an output of the inverter to the windings of the rotor, the inverter supplying power to the rotor windings at the adjustment frequency, characterized in that: the stator has a quadrature winding shifted 90 degrees from main winding and the method comprises the step of operatively connecting the DC link of the inverter to the quadrature winding of the stator to provide the DC link with current. operatively connecting the output of the stator (33a-33c) to an input of an inverter, the inverter receiving the output voltage at the frequency; and operatively connecting an output of the inverter to the windings of the rotor, the inverter supplying power to the rotor windings at the adjustment frequency, characterized in that: the stator has a quadrature winding shifted 90 degrees from main winding and the method comprises the step of operatively connecting the DC link of the inverter to the quadrature winding of the stator to provide the DC link with current.