SYSTEMS CONTAINING A DOUBLE FED INDUCTION MACHINE AND A FLY WHEEL, AND METHODS OF OPERATING SUCH SYSTEMS

A system contains a double fed induction machine having a stator and a rotor, a fly wheel coupled to the rotor, and a control device for providing a rotor voltage and a rotor current to the rotor. The control device is connected to the rotor and the stator and is capable of generating the rotor voltage and rotor current in response to an electrical signal that is applied to the stator. The control device has a multilevel converter and a control unit for controlling the multilevel converter.