Open-loop control for transient operation of a rotary electric machine

An electric powertrain comprising:

• a variable flux machine (VFM);
• a traction power inverter module (TPIM) connected to the VFM;
• and
• a controller in communication with the VFM and the TPIM, and configured to:
• during a shunt angle transition of the VFM, receive a commanded shunt angle and a measured shunt angle of the VFM when operating the VFM in a predetermined control region;
• calculate a d-axis delta current (ΔId) term and a q-axis delta current (ΔIq) term required to maintain an output torque level of the VFM through a duration of the shunt angle transition;
• and
• apply the required ΔId term and the required ΔId term as feed-forward terms to respectively adjust a d-axis current (Id) term and a q-axis current (Iq) term from a respective lookup table, and to thereby maintain the output torque level of the VFM during the shunt angle transition.

A method for controlling transient operation of a permanent magnet (PM) machine, the method comprising:

• during operation of the PM machine in a maximum torque per ampere (MTPA) control region, receiving a commanded temperature and a measured temperature of the PM;
• calculating, via a controller using the commanded temperature, the measured temperature, a commanded d-axis current, and a commanded q-axis current, a d-axis delta current (ΔId) term and a q-axis delta current (ΔIq) term required to maintain an output torque level of the electric machine through a change of temperature of the PM machine in the MTPA region;
• providing a direct current bus voltage, a torque slew command, and a rotary speed of the PM into separate d-axis and q-axis current command lookup tables;
• determining the Id term and the Iq term via the separate d-axis and q-axis current command lookup tables using the direct current bus voltage, the torque slew command, and the rotary speed;
• and
• applying the required ΔId term and the required ΔId term as feed-forward terms to respectively adjust the Id term and the Iq term, thereby maintaining the output torque level of the VFM during the shunt angle transition.