PMSM Motor Drive with Current Direct Digital Control and Near 1st-Order Speed Control

This paper presents a permanent-magnet-synchronous-motor (PMSM) drive with the three-phase three-wire inverter current direct digital control (DDC). The DDC achieves high accuracy and fast response, and expresses duty ratios as analytical functions without any parameter tuning. Thanks to the proposed current DDC, the fast response can simplify the conventional double-loop speed-current control system to a single-loop one, allowing a simple speed control design. Thus, this paper also presents how to design the simple speed-control law based on deadbeat and disturbance-observer-based control, achieving near 1st-order response. Besides, the low-speed cogging torque issue is addressed with the virtual cogging torque (VCT) control. Experimental results confirm the accurate and fast current/torque tracking, near 1st-order speed response, and stable low-speed VCT control.