Improved low speed performance of a PI-DTC interior PM machine with compensations of dead-time effects and forward voltage drops

The performance of direct torque control (DTC) interior permanent magnet (IPM) machines at low speed is poor due to a few reasons, namely limited accuracy of stator voltage acquisition and the presence of offset and drift components in the acquired signals. Due to factors such as forward voltage drop across devices in the three phase inverter and dead-time of switching devices, the voltage across the machine terminals differ from the reference voltage vector used to estimate stator flux and electromagnetic torque. This can lead to instability of the IPM drive during low speed operation. Compensation schemes for forward voltage drops and dead-time are implemented, resulting in better performance of the PI DTC IPM drive.