Startup Scheme for Shaft-Sensorless PMa-SynRM Drives for Fan and Pump Applications

This article introduces an innovative integrated shaft-sensorless control strategy for a permanent magnet assisted synchronous reluctance motor (PMa-SynRM) for fan and pump applications. The strategy is designed to optimize start-up performance by addressing key shaft-sensorless challenges, including initial rotor position estimation, robust starting and low-speed field oriented control (FOC). To determine the initial rotor position and magnet orientation, a combination of rotor parking method that utilizes a low dc current and brief high-frequency (HF) voltage injection is proposed, taking advantage of inherent asymmetrical rotor parking positions of PMa-SynRM. By this, application of high opposite current pulses for weak magnet polarity detection is avoided. Sensorless FOC close to zero speed is achieved by combining HF test signal injection and integration-free extended electromotive force (EEMF) algorithm with phase-locked loop upgraded with the newly proposed EEMF boost. The proposed strategy also incorporates new optimal torque control strategy with unity gain and minimal copper losses, enhancing dynamic torque production for rapid startup from zero speed. Experiments on low-cost PMa-SynRM sensorless drive designed for pump application demonstrate the effectiveness of the proposed strategy.