| Abstract |
We in this paper consider reduced-order observers for rotor flux estimation of induction motors. The
traditional ”current” and “voltage” models are shown to be special cases. It is also shown that the
flux dynamics form a nonlinear closed-loop system when the flux estimate is used for field orientation.
Proper observer gain selection is essential for good behavior of this system. A framework is developed,
in which the properties of any gain selection can be assessed with ease. Candidate gain selections
are considered, two of which yield schemes that do not use the rotor speed in their equations (socalled
inherently sensorless schemes). It is finally shown that for any gain selection, an equivalent
synchronous-frame implementation (i.e., indirect field orientation) always exists. |
