Digital implementation of predictive direct control algorithms for induction motors

To achieve fast control action, direct control methods should be used. Two new types of those are presented in this paper. (1) "Direct mean torque control" (DMTC) combines the good dynamic performance of direct torque control with the advantages of inherently constant switching frequency and time equidistant control for implementation in a digital signal processor. (2) Presently, speed control of electrical drives is preferably done by cascaded control loops. To improve dynamic performance of speed controlled drives, a "direct speed control" (DSPC) method is proposed. The switching events of the inverter are directly calculated in such a way, that in steady state the speed of the drive is kept in an (extremely small-) hysteresis band and a disturbed system will return to steady state as fast as possible, i.e. time-optimal.