Reduction of machine current distortion using direct self control (dsc) for high‐power three‐level gto‐inverters

Direct Self Control (DSC), developed for voltage‐source inverter‐fed induction motors, is an efficient and highly dynamic control method for inverters in the MW‐range with a limited switching frequency up to 200 Hz… 250 Hz, It is based on control ofstatorflux in a stator‐fixed reference frame; in the region below rated statorfrequency a two‐level torque controller adjusts the voltage directly so that no Pulse‐Width Modulation (PMW) is necessary. Three‐level inverters, which are best suited for very high voltage and high power demand, have several additional advantages compared to two‐level inverters, e. g. the pulsation of torque can be reduced as well as the machine current distortion. In this paper an improved two‐level torque control strategy for three‐level inverters with less current distortion is described and the practical results of its application based on measurements at a 22 kW experimental machine set are discussed.