Sensorless Speed Control and High-Performance Fault Diagnosis in VSI-Fed PMSM Motor Drive Under Open-Phase Fault: Analysis and Experiments

  • Mongi MoujahedEmail author
  • Hechmi Benazza
  • Mohamed Jemli
  • Mohamed Boussak
Research Paper


This paper aims to provide a high-performance sensorless fault-tolerant direct torque control of permanent magnet synchronous motor based on nonlinear position and speed observer. The nonlinear observer is based on a trigonometric function to estimate the rotor position, and a proportional–integral controller is used to estimate the speed from estimated position. A faulty leg (open phase) in the PWM VSI changes the corresponding terminal voltage and introduces the voltage distortions to each phase voltage. The ordinary two-level inverter is composed of three legs. In the proposed fault-tolerant inverter, a redundant leg is added that replaces the faulted leg. The detection of the open-phase fault is based only on the current signals and the maximum threshold they exceed that in case of fault.


Permanent magnet synchronous motor (PMSM) Nonlinear observer PWM VSI FTDTC Sensorless control Position and speed estimation 

List of symbols

d, q

Two-axis synchronous frame quantities

α, β

Two-axis stationary frame quantities

\(V_{d} , V_{q}\)

d- and q-axis components of stator voltage

\(i_{d} ,i_{q}\)

d- and q-axis stator current on rotating frame


Number of pole pairs


Armature winding resistance

\(L_{d} ,L_{q}\)

d- and q-axis stator self-inductances


EMF constant


Torque constant

\(T_{\text{e}} ,T_{\text{l}}\)

Electromagnetic and load torque

\(\hat{\varPhi }_{\text{m}}\)

Peak permanent magnet flux linkage

J, f

Rotor inertia and viscous friction

\(\theta_{\text{r}} ,\omega_{\text{r}}\)

Rotor position and angular velocity at electrical


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Copyright information

© Shiraz University 2018

Authors and Affiliations

  • Mongi Moujahed
    • 1
    Email author
  • Hechmi Benazza
    • 1
  • Mohamed Jemli
    • 1
  • Mohamed Boussak
    • 2
    • 3
  1. 1.Laboratoire d’Ingénieries des Systèmes Industriels et des Energies Renouvelables (LSIER)Université de Tunis, Ecole Nationale Supérieure d’Ingénieurs de Tunis (ENSIT)TunisTunisia
  2. 2.Centrale MarseilleMarseille Cedex 20France
  3. 3.Laboratoire des Sciences de l’Information et des Systèmes (LSIS) – UMR CNRS 6168MarseilleFrance

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