Efficient control of low inductance brushless DC motors based on LC filtering and active damping

Brushless DC motors (BLDC) present several technical advantages with respect to conventional permanent magnets synchronous motors. These advantages include higher rotational speeds, reduced construction complexity and simpler control strategies. This paper discusses a cost-effective control strategy for BLDC motors characterized by low stator inductance. The proposed technique is based on an LC filter inserted between the inverter output and the motor. The filter capacitors are controlled such that three DC voltages are applied to the stator terminals. An active damping approach is used to control stator currents and prevents voltage oscillations. Compared with existing solutions, this technique simplifies the hardware implementation of such a drive system and offers a notable reduction in the switching frequency with minimal values of the magnetic elements. In addition, high frequency torque ripples are significantly reduced. The design procedure of this controller is presented in this paper and the performances are compared with the conventional control technique.