Passivity-based control for phase-locked loop induction motor drive

This paper designs a nonlinear feedback controller for a phase-locked loop (PLL) induction motor drive using a passivity-based control (PBC) principle. First, the dynamics of the induction motor are described in a Euler-Lagrange form. The PLL technique is introduced for the speed control to obtain precise steady speed. The reference (steady-state) behavior for all state variables are defined according to the dynamics of PLL and field orientation strategy. The best advantage of the feedback controller by passivity-based control principle is global stability, since the energy balance equation of an induction motor is used. As the dynamic of the PLL is taken into consideration in the design procedure, this stability indicates that lock-in of PLL is ensured, in spite of the nonlinear characteristics of the PLL. Since the same idea as a field orientation strategy is used, the same performance as field orientation is obtained. However, the rotor flux observer is no longer needed. On the basis of the nonlinear feedback controller, a nonlinear state observer and adaptive scheme for rotor resistance and load torque estimation are also designed. Some simulation results illustrate the performance of this PBC system