Direct torque control of AC machines

The DTC technology has been steadily developed for induction motors initially and now in a mature stage where its adaptation in commercial products has been accepted by industry. The development focus is now toward adaptation of DTC into complex applications requiring special motor types and drive topologies. The various technology areas are special machines for high-speed applications and multiphase machines with more than three-phase windings. There are attempts to extend DTC strategies for advanced drive topologies like matrix converters, multilevel converter topologies, integrated line side converter control. The complexity in such topologies is coming from increased number of voltage vector combinations, which are available for switching, and thus, decision-making can be a complex and time-consuming process. This is typical situation in even more complex multilevel converter fed multiphase machine architecture where the number of voltage vector combinations rises exponentially with machine phase and converter voltage levels.