Compensation of unbalanced conditions in a PMAC motor with an optimal state estimator

Unbalanced operation of a PMAC motor results in torque pulsations that adversely affect position and velocity servo systems. These torque pulsations vary with the rotor position and are reflected as speed ripple which degrades the performance of the PMAC drive. This thesis explores the application of the Decomposition of Instantaneous Sequence Components (DISC) transformation for torque ripple minimization in PMAC motors. The general theory of DISC transform is explained and its advantages over other three phase analysis methods are also discussed. The application of the DISC transform results in a set of state space equations, that can be used to analyze the PMAC motor system. The aim is to compensate for the imbalances in the PMAC motor system, by actively controlling the different DISC currents, and thereby reducing the torque ripple. Simulations are done to verify the validity of the DISC model for a PMAC motor. Then the design of a Kalman observer for state estimation and an LQR controller are detailed. Simulation of the system using the designed state observer and controller show reduction in the imbalance and torque ripple.