Analysis, Modeling, and Current Trajectory Control of Magnetization State Manipulation in Variable-Flux Permanent Magnet Machines

Magnetization and demagnetization current control is a critical part of the variable-flux permanent magnet machine control, but the variable-flux properties and saturation effects deteriorate conventional current controller performances. Thus, this paper proposes an improved feed-forward current controller that compensates voltage variations during the magnetization and demagnetization manipulations, obtaining better control performances. The compensation voltages are analyzed by finite-element method, and a modified mathematical model is developed to present the relation among the voltages, the flux linkages, and the manipulation currents. This model considers induced voltage and variable electromotive force, which are caused by the change of the permanent magnet flux linkage during the manipulations. Based on the model, the induced voltage, the cross-coupling rotating voltage, and the resistance voltage are compensated in the proposed feed-forward controller. This controller is verified by experiments, showing fast response and accurate trajectory tracking advantages.