Identification and compensation of high-order harmonic distortions in saliency based sensorless control of induction machines

The basic spatial modulation effects of induction machines caused by slotting and saturation, have been analyzed for exploitation in speed sensorless control. With increasing load level, additional spatial harmonics arise, acting as disturbance and deteriorating sensorless control performance. In view of the fact, that induction machines for application in traction systems (e.g. public or cargo transportation) are operated at a high level of excitation, higher harmonic numbers especially of the spatial saturation become dominant and need to be compensated in order to establish speed sensorless operation. It can be observed, that especially the first order harmonic of spatial saturation shows a significant rise in magnitude when load current is increased. The presented paper thus focus on the investigation of high order spatial modulations and their deterministic properties with the goal to establish an efficient compensation of their disturbing effects. Based on the identified deterministic properties a compensation method is proposed and tested through measurements on a 15kW induction machine.