Universal Field Oriented Controller with Indirect Speed Sensing Based on the Saturation Third Harmonic Voltage

A sensorless universal field orientation controller (UFO) based on the estimation of rotor speed and air gap flux from the third harmonic component of the stator phase voltages was developed and implemented. One of the objectives is to develop a torque controlled induction motor drive system with reduced number of sensors in order to reduce total drive hardware complexity and costs. The third harmonic stator voltage component, due to the stator and rotor teeth saturation, is used to estimate the motor air gap flux and rotor speed. It is shown that the third harmonic stator voltage is modulated by a high frequency component due to the rotor slots. It is also shown how this high frequency component is extracted from the third harmonic signal and used to estimate the rotor speed. The concept of universal field orientation (UFO) was applied, and a controller was developed and prototyped in the laboratory. The general structure of the UFO and its ability to commutate from one reference frame to another as the drive operating conditions change was the main reason for its adoption Experimental results show that the drive system has a good performance