An improved flux observer based on PLL frequency estimator for sensorless vector control of induction motors

Mihai Comanescu, Longya Xu

Research output: Contribution to journalArticle

140 Scopus citations


This paper presents an improved method of flux estimation for sensorless vector control of induction motors based on a phase locked loop (PLL) programmable low-pass filter (LPF) and a vector rotator. A PLL synchronized with the voltage vector is used for stator frequency estimation. The pure integration of the stator voltage equations is difficult to implement and LPFs with a fixed cutoff provide good estimates only in the relatively high frequency range - at low frequencies, the estimates fail in both magnitude and phase. The method proposed corrects the above problem for a wide range of speeds. Simulations and experimental results on a 0.25-hp three-phase induction machine verify the validity of the approach.

Original languageEnglish (US)
Pages (from-to)50-56
Number of pages7
JournalIEEE Transactions on Industrial Electronics
Issue number1
StatePublished - Feb 1 2006


All Science Journal Classification (ASJC) codes

  • Control and Systems Engineering
  • Electrical and Electronic Engineering

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