Occurrence and suppression of DC-flux deviations in a doubly-fed flywheel generator system

This paper deals with DC-flux deviations occurring in a doubly-fed flywheel generator with stator-current feedback control. An AC output voltage of the PWM inverter connected to the rotor produces the DC-flux deviations in the stator. It is difficult to detect the DC flux from the stator current and/or voltage, because the DC flux induces no electromotive force on the stator windings. This paper proposes a new control method for suppressing the DC flux deviations based on calculating the magnetizing current from the stator and rotor currents. Experimental results verify the viability of the proposed control method.