Time Optimal, Loss Minimizing Current Trajectory for Interior Permanent Magnet Synchronous Machines in Overmodulation

This paper describes a minimum loss and fast dynamic torque control for interior permanent magnet synchronous machine (IPMSM) drives operating in overmodulation. Within the voltage limits, the desired air gap torque can be achieved by the end of one PWM switching cycle using current regulator under maximum torque per ampere (MTPA) trajectory. However, in overmodulation operation due to voltage limits, it may take a finite number of steps instead of one single step to achieve the desired air gap torque. In this case, a finite sequence dynamic optimal trajectory is tracked to achieve either minimum loss or minimum time (time-optimal) control. The dynamic programming optimization technique is employed in this paper to derive both the minimum loss and the time optimal current trajectories.