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This thesis proposes a novel deadbeat (DB) direct torque and active flux control for interior-permanent-magnet-synchronous-machine (IPMSM). It presents a new framework for DB control where the active flux, instead of the stator flux, is used as a control variable along with the torque. Unlike the conventional DB controls for IPMSM, the proposed method becomes a decoupled control that significantly reduces the complexity of calculating the DB stator voltage vector. It also improves control performances by reducing torque/current and flux ripples over conventional DB direct torque and flux control for IPMSM. In addition, this thesis proposes a new disturbance observer for parameter uncertainties and time delays. The robustness of DB control against parameter uncertainties improves by feedforward compensation of disturbance functions, which the observer estimate. An accurate estimation of active flux, torque and disturbance functions reduces the tracking errors of torque and active flux. This thesis also focuses on obtaining optimal control references for the proposed DB method analytically. It presents the formulations of control trajectories and constraints in the new torque-active flux plane considering inductance variations. The new control strategies (or trajectories) such as maximum torque per active flux (MTPAF) and active flux weakening (AFW) and their constraints not only feature simplicity but also improves accuracy. The simplified analytical solutions for such strategies are also deduced to overcome the problem associated with the conventional offline (e.g.look-up-table based method), numerical and other analytical methods. Thus, the proposed MTPAF and AFW control reduce the computational burden and enhance the accuracy compared to the conventional control strategies. The proposed AFW approach enhances the accuracy of the FW operation and thus improves the machine’s efficiency without increasing the computational burden. In contrast to conventional FW operation, the critical operation along the current limit boundary is obtained by introducing an offset-speed-based solution without solving the highly non-linear optimization problem in the proposed AFW approach. The proposed AFW is more accurate than the conventional method because the control references are obtained from the voltage constraint without neglecting or compensating for the stator resistance voltage drop. Theoretical analysis and extensive experimental results have demonstrated the effectiveness of the proposed method. In this thesis, the problems associated with the DB control for IPMSMs, namely coupled control, computational burden, parameter uncertainties, wide speed operation, accurate control trajectories, and simplified analytical solutions of control trajectories, have been resolved to a much greater extent. As a result, the proposed DB control will be a viable candidate for future wide-speed IPMSM drives. |
