System and method for permanent magnet assisted synchronous reluctance motor control from zero or low speed

A method for determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor, wherein the sensorless permanent magnet assisted synchronous reluctance motor includes a stator having a three-phase stator winding configuration and a rotor including a magnetic permeability core having a plurality of flux barriers that hold a plurality of permanent magnets and a plurality of surface bridges, wherein the plurality of permanent magnets generate a plurality of rotor magnetic poles having magnetic polarity, the method for determining magnetic polarity comprising:

• demagnetizing directionally magnetized flux density in a first one of the plurality of surface bridges, and
• further magnetizing the flux density in a second one of the plurality of surface bridges;
• applying positive and negative voltage pulses to the three-phase stator winding configuration of the rotor;
• detecting a current response to the positive voltage pulse;
• detecting a current response to the negative voltage pulse;
• determining the magnetic polarity of the plurality of magnetic poles based on the current response to the positive voltage pulse and the current response to the negative voltage pulse.

A method for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during startup, wherein the sensorless permanent magnet assisted synchronous reluctance motor includes a stator having a three-phase stator winding configuration and a rotor including a magnetic permeability core having a plurality of flux barriers that hold a plurality of permanent magnets and a plurality of surface bridges, wherein the plurality of permanent magnets generate a plurality of rotor magnetic poles having magnetic polarity, the method for determining magnetic polarity comprising:

• characterizing surface bridge flux density over a range of positive and negative d-axis current values for a sensorless permanent magnet assisted synchronous reluctance motor having a particular configuration;
• identifying a d-axis current value and corresponding d-axis reflection current value, wherein the d-axis current value demagnetize the surface bridge flux density to maintain or achieve leakage flux magnetic desaturation, and wherein the corresponding d-axis reflection current value magnetize the surface bridge flux density to maintain or achieve leakage flux magnetic saturation;
• selecting a pair of polarity detection voltage pulses such that one of the polarity detection voltage pulses produces the identified d-axis current value that that demagnetizes the surface bridge flux density and the other one of the polarity detection voltage pulses produces the identified corresponding d-axis reflection current value that magnetizes the surface bridge flux density.