Stability Analysis of Vector Control of Induction Motor without Speed Sensor Taking into Account the Effects of Current Control Loop.

Abstract

The conventional method of vector control has been slip-frequency control. This method reduces the structural features of squirrel-cage induction motor and restricts the applications because it requires a speed sensor. Stability analysis of the vector control system have been made by considering only ideal current control loop. In this paper, we analyze exactly the stability analysis of the vector control of induction motor without speed sensor, taking into account the effects of PI current loop and rotor flux feedback. A transfer function between the rotor speed wr, and the rotor speed command wr*; can be obtained by standard small signal analysis techniques. For this purpose, it is convenient to use a dq synchronous reference frame rotating together with rotor flux and to allow small signal perturbations in the primary currents i1d, i1q, secondary currents i2d, i2q, calculated primary current commands _??_, _??_, calculated rotor flux commands _??_, _??_, rotor speed ωr, and estimated rotor speed _??_. Furthermore, theoretical step responses of the rotor speed are compared with the experimental results.