Abstract: Disclosed herein is a system including a generator/motor subsystem configured to interchangeably impart and receive mechanical force; a stiff DC bus; and power conditioning circuitry electrically connected between the generator/motor subsystem and the stiff DC bus, the power conditioning circuitry conditioning electrical power received from the stiff DC bus to control the angular speed of a rotor of the generator/motor subsystem when imparting mechanical force, and also conditioning electrical power generated for provision to the stiff DC bus by the generator/motor subsystem when receiving mechanical force.