Bearingless brushless DC (BBLDC) motor in the flywheel energy storage system has advantages of low energy consumption, high critical speed and better speed adjustment performance. However, torque ripple exists inevitably due to the current commutation of the BBLDC motor and the wide range of speed changes when the flywheel energy storage system charges and discharges. In this frame, an approach of combining the direct torque control (DTC) with the current prediction control (CPC) is proposed to suppress torque ripple in wide speed regulation range. In this paper, the mathematical model of the BBLDC motor is given, and the principle of DTC scheme is introduced. On the basis of analyzing the causes of commutation torque ripple when using DTC scheme, CPC scheme is employed to minimize the commutation torque ripple by controlling the changes of phase current during commutation. During the non-commutation, the DTC is selected, and the CPC is selected during the commutation. Results show that the proposed approach is feasible, and torque ripple is effectively suppressed both in high speed and low speed. Moreover, this method has no effect on the suspension performance.
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