SVPWM method for performance improvement of direct torque control

A SVPWM (space vector pulse width modulation) predictive control method was developed to solve the problems of direct torque control (DTC) for induction motors related to the uncertainty of the switching frequency, the flux ripple, and the torque ripple. A u-n model is used to determine the actual stator flux and the torque and flux errors so that the method can then calculate the reference voltage space vector that can compensate for the errors. Finally the reference vector is then synthesized by a SVPWM algorithm. The voltage and flux errors at the sampling instant can then be compensated for in the next control period, so the errors are always kept small, which leads to small fluxes and torque ripple. The SVPWM algorithm keeps the switching frequency constant. Simulations and experiments show that torque and flux ripples are small with a constant switching frequency of less than 3 kHz.