Abstract:
This dissertation report describes the investigation of sensor less control methods of
Induction machines for low speed operation.
Requirement of low cost, low maintenance, robust electrical motors has resulted in the
emergence of the AC Induction motor as the industry leader. Induction motors have been
used more in the industrial variable speed drive system with the development of vector
control technology. This method requires a speed sensor such as shaft encoder for speed
control. Sensors used in electric drives degrade the reliability of the system especially in
hostile environments and require special attention to electrical noise. Moreover, it is difficult
to mount sensors in certain applications in addition to extra expenses involved. The induction
motor drives without mechanical speed sensors have low cost and size and high reliability.
IM is mathematically modelled to get an approximate idea of the actual plant model. The
vector control of IM is implemented by using PI controller. To make the system sensor less,
we go for rotor speed estimation using MRAS technique along with Popov’s hyper stability
criteria. MRAS identification is performed with three methods based on rotor flux, back emf
and reactive power as the state variables. The different simulation results are observed and
studied and the analysis of the different simulated results are presented.
The dynamic performance of the estimators is analysed for parameter variations with
particular focus on low speed operation. The Reactive power based MRAS method is
observed to be the best method and tested with experimental setup on 400V test bench.
