A novel control strategy for BLDCM applied in flywheel energy storage system based on unipolar and bipolar control

The brushless DC machine (BLDCM) is very appropriate for driving flywheel energy storage systems (FESS) for wind-energy applications due to its high torque, high efficiency and wide speed range. To store and release more energy, a novel control strategy combining bipolar and unipolar controls based on a converter with a neutral point controlling bridge arm is proposed. The freewheeling current in the non-energized phase is eliminated by series-opposing transistors in each half bridge. The mathematical model of the FESS containing a BLDCM and an improved converter is established and the proposed control strategy is then simulated by Matlab/Simulink. The simulation results verify the correctness and the effectiveness of the designed converter as well as the proposed control strategy.