Discrete-time physical limits-based enhanced finite-settling-step direct torque and flux control for IPMSM drives

This paper proposes an enhanced direct torque and flux control method using the discrete-time version of the physical constraints to complete the finite-settling-step direct torque and flux control (FSS-DTFC) algorithm with a constant switching frequency. Successful application of the control approach has been corroborated by a graphical and analytical analysis that naturally leads to a single voltage selection policy for the discrete-time current limit (DTCL)-based FSS-DTFC. The algorithm has the advantage of providing adequate results over the number of potential secondary upsets found in the steady-state current limit (SSCL)-based DTFC. The proposed voltage selection rule enables the motor to track the fast changes in torque and stator flux linkage, which improves dynamic responses significantly over a wide constant-power operating region. The control strategy has been evaluated on a 900W IPMSM in both simulation and experiment.