A Novel Driving Strategy for the APMSM Based on Half-Bridge Topology with Midpoint Voltage Balancing

The intelligent annular transmission system, driven by a permanent magnet synchronous motor, comprises linear stators, arc stators, and multiple passive movers. This system finds widespread application in material handling and packaging production. This article proposes a coil current independent control method with a single coil as the fundamental control unit, which breaks through the concept of 'phase' in the traditional motor control system and controls the current amplitude and phase of the coil coupled with the mover independently, thereby minimizing the distance between the movers and reducing the copper loss of the motor. The mathematical model of the annular permanent magnet synchronous motor (APMSM) is established based on the proposed driving strategy and validated using the finite-element method. Furthermore, a half-bridge circuit is adopted as the power conversion topology to reduce the number of power transistors. To address the midpoint voltage ripple caused by the zero-sequence current in the half-bridge circuit, the voltage and current closed-loop controller is constructed by adding a bridge arm. Finally, an experimental platform based on a field-programmable gate array (FPGA) general-purpose chip and digital signal processor (DSP) was built to verify the effectiveness of the proposed driving strategy.