Further development of direct self control for application in electric traction

Direct self control was primarily developed for optimal steady-state and dynamic torque quality at the low switching frequencies of high power traction inverters. Though DC line harmonics and peak inverter current can be compared with those of PWM drives with same switching frequency there are now new possibilities by new digital signal processors to improve that too. The 6-pulse DC link reaction of the inverter is cancelled by introducing an eighteen-corner track curve. The same track curve can be employed advantageously with blocked pulsing as synchronous switching mode to avoid subharmonic torques in the high speed area. A current limitation detaching the torque two-level control increases the average torque up to 24% with same peak current, but with increased torque pulsation. The excellent dynamic properties of all DSC modes show how DSC is suited optimally for electric traction