System and method for controlling a permanent magnet-assisted synchronous reluctance motor from standstill or low speed

Abstract

Sensorless permanent magnet assisted synchronous reluctance motor (300), comprising: a stator (223) mounted with a three-phase stator winding configuration (158); a rotor (225, 116) comprising a magnetically permeable core having multiple flux barriers (115) that divide the core into multiple main rotor flux path segments (120) to control the magnetic flux within the rotor (225, 116), wherein the multiple flux barriers (115) hold multiple permanent magnets (117), the magnetically permeable core comprising multiple surface bridges (B1, B2, B3) that connect the multiple rotor flux path segments (120) to each other, the rotor (225, 116) being rotatable relative to the stator (223) via the excitation of the three-phase stator winding configuration (158) of the stator (223), the multiple permanent magnets (117) generating multiple rotor magnet poles possessing a magnetic polarity; a main magnetic flux path between at least one of the several rotor flux path segments (120) and the stator (223); a load-free magnetic leakage flux path through at least one of the several surface bridges (B1, B2, B3) which have a directed magnetized flux density caused by at least one of the several permanent magnets (117); a motor control system (224, 226), have: a power supply (441); a sensing circuit (443) configured to sense one or more electrical characteristics of the stator (223); a controller (444), configured for: Applying a positive voltage pulse and a negative voltage pulse to the three-phase stator winding configuration (158), wherein, to determine the magnetic polarity during motor start-up, the magnitude of the positive voltage pulse and the negative voltage pulse is selected based on achieving predetermined changes in flux saturation states within the surface bridges such that: one of the positive voltage pulse and the negative voltage pulse demagnetizes the directed magnetized flux density in at least one of the several surface bridges (B1, B2, B3) and the other of the positive voltage pulse and the negative voltage pulse further magnetizes the flux density in at least one of the several surface bridges (B1, B2, B3); Detecting a current response to the positive voltage pulse and a current response to the negative voltage pulse; Determining the magnetic polarity of multiple magnetic poles based on the relative orders of magnitude of the current response to the positive voltage pulse and the current response to the negative voltage pulse; Generating control commands during motor start-up based on the specific magnetic polarity of the multiple magnetic poles; and a control circuit (442) for generating excitation signals for the three-phase stator winding configuration (158) of the stator (223) according to the control commands during motor start-up.

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