| Abstract |
Sensorless indirect field oriented inductionmotor drives using information in the fundamental excitation
(back-emf) for speed estimation are considered. It is shown that instability phenomena which are not
present for sensored operation occur, both for nominal and low speeds. The problems at nominal
speeds are remedied by adding a term to the standard slip relation, such that approximate "voltage
model" characteristics are obtained. The low-speed problems are remedied by careful choice of the
model machine parameters and the torque-producing stator current component. It is also shown how
a simple speed estimation algorithm based on a voltage error can be designed. As no state observer is
required, the sensorless control system is computationally very efficient. |
