Voltage- and Current- Limited Operation of Deadbeat-Direct Torque and Flux Control for Interior Permanent Magnet Synchronous Machines

This document presents implementation of deadbeat-direct torque and flux control (DB-DTFC) for an interior permanent magnet synchronous machine (IPMSM) at voltage- and current- limited condition and robustness evaluation of a DB-DTFC IPMSM drive with respect to parameter variations. When a motor is operated at voltage- and current- limits, a transient torque response becomes slow due to lack of voltage to develop torque changes. Many solutions have been presented and focused on a full utilization of inverter voltage instead of improving transient torque responses. A few methods have addressed optimal solutions to achieve fast torque responses but algorithms are complicated to implement in real time. This research presents development of time optimal and real time suboptimal control algorithms to improve transient torque dynamics of an IPMSM drive at voltage and current limits. Also, loss minimizing stator flux linkage is used during steady state operation to reduce computational complexity of optimization and to operate IPMSM drives at the loss minimizing condition. The voltage- and current- limited operation of IPMSM drives is implemented and evaluated in simulation and in experiment. This research also presents robustness evaluation of DB-DTFC of IPMSM drives with respect to machine parameter variations. For performance comparison, current vector control (CVC), one of the most widely used control methods, is also implemented under identical operating conditions as DB-DTFC. As the metrics to evaluate dynamic performance of DB-DTFC and CVC IPMSM drives, command tracking is used to investigate torque command tracking performance and dynamics stiffness is used to evaluate disturbance rejection performance. In addition, the torque estimation accuracy of DB-DTFC and CVC is investigated with respect to parameter variation. Simulation and experimental results of robustness evaluation of DB-DTFC and CVC are presented.