Optimum Current Control in the Field-Weakened Region for Permanent Magnet AC Machines

This paper presents current regulation algorithm for permanent magnet AC machines that provides smooth transition in the entire field-weakened region. The algorithm offers robust and simple current regulation with maximum torque capability for permanent magnet AC machines despite significant changes in the voltage source and machine parameters. The algorithm identifies when the machine enters field-weakened region and determines the optimum d-axis and q-axis current command for the machine. In addition, the algorithm identifies when the machine reached the maximum torque per flux and it regulates current accordingly. Simulation and experimental results are presented, which prove the algorithm functionality.