Optimized sensorless DTC of PMSM for electric vehicles by using a switching command synchronized evaluation at standstill and low speed

The “direct-torque-control” (DTC) is an alternative to the commonly used “field oriented control” (FOC) for the control of a PMSM. One advantage of the DTC is its inherent ability of sensorless control. However at standstill and low speed range the back-EMF based model has problems to detect the rotor position. The switching command synchronized evaluation (SCSE) calculates the rotor position using the current change during active voltage vectors. Realizations of the SCSE using the FOC are known, but the combination of the SCSE with a discrete-time DTC avoids problems with switching disturbances. The capability of the presented optimized DTC is proved with measurements on a test bench.