文档介绍：Analysis and Improvement of Low Frequency Control of
Speed-sensorless AC Drive Fed by Three-level Inverter
Jie (Jay) Chang, ., Sr. Member IEEE
Florida State University, Florida, 32310,
Abstract - In induction machine drive without a speed remains more to be desired. The motor current distortion
sensor, the estimation of the motor flux and speed often es significant at low frequencies.
es deteriorated at low speeds with low back EMF. Our
analysis shows that, in addition to the state resistance On the other hand, the thermal variation of the stator
variation, the estimated value of field orientation angle is resistance has been identified for adversely affecting the
often corrupted by accumulative errors from the integration control at low speeds [11]. However, there exist other error
of voltage variables at motor terminals that have low sources in a practical drive system that might have
signal/noise ratio at low frequencies. A repetitive loop path significant impact on the drive control, which is to be
of integration via the feedback path can amplify this type of detailed in this paper.
error, thus speeding up the degradation process. The control
system runs into information starvation due to the loss of Upon reviewing the practical control approach, a detailed
correct field orientation. The machine's spiral vectors are analysis of the error