Sliding mode control of a three phase induction motor based on reference model

Almost controllers of induction motor speed are designed to keep motor speed unchanged. It is hard for conventional controller such as PI controller because induction motor is a nonlinear system with parameter changes and noise. Sliding mode control based on reference model is worth trying to overcome that difficulty. This paper presents a new method using sliding mode controller based on reference model and stator field orientation for an induction motor. There are two separate sliding mode controllers are designed. The first one is for control of the flux field and the second for the torque of the motor. A reference model is properly chosen to estimate reference speed of the motor. A seven level cascade inverter is control to reduce common - mode voltage which will improve the stability for proposed controllers. The method used to reduce chattering around sliding surfaces is also presented. Simulation and experimental results on a 1-hp 150-rad/sec squirrel-rotor induction motor shows smooth operation of the control scheme with a 1.5 times increase of the stator resistor and rotor resistor values of the induction motor under condition of noises. The performances of the sliding mode controllers are compared with a PI (Proportional and Integral) controllers with various load conditions.