Digital control techniques for converters in variable speed drives

Inverters can be seen as a sort of digital-analog-converter. Therefore it seems natural to control them by digital feedback circuits including microprocessors. This paper describes the digital control of an inverter-fed induction motor with shortcircuited rotor windings and of a subsynchronous converter cascade with a slip-ring induction motor by a multimicrocomputer system. Different control techniques and strategies are given and results from a drive system with an induction motor - DC-generator set are presented.