Abstract
D.Ing.
In this document the research related to the development of a microprocessor based field
oriented controller is presented. An overview of the state-of-the-art is presented, with specific
reference to all the different aspects related to the development of variable speed induction
machine drives.
During the development of it is necessary to use accurate system models. Such models are
most useful when incorporated in a simulation program. In chapter 2 such a simulation
program is described. Included in the simulation program are accurate models for the inverter
and the induction machine. Effects such as resistance variation due to heating and inductance
variation due to saturation are included. Modulation of the inverter output voltage wave from
by the load current caused by the snubbers is also included.
The development of a rotor current estimation strategy is presented in chapter 3. During the
development extensive use was made of the simulation program. A new stationary reference
frame current controller is also presented in chapter 3. Finally the implementation of the
proposed field oriented controller is presented in chapter 4. As part of this a dual mode speed
control algorithm was developed and implemented.