Three phase inverter speed control of AC drives motor using DSPic microcontroller

Abstract

AC drives based on full digital control have reached the status of a maturing technology in a broad range of applications, ranging from low-cost to high performance systems. In the field of the drive of the electric machines, the elimination of the mechanical speed sensor can present an economic interest and improve safety of operation. With speed estimation, sensorless vector control is possible, meaning that the speed of induction machines without mechanical speed sensors can be controlled. The flux observer is expanded into a combined flux and speed observer, measuring only stator current and voltage. In this work, we develop algorithms of three phase inverter control of IM without speed sensor using DSPic microcontroller. We present two types of speed estimators based on the mathematical model of the machine. The first estimator is called MRAS (Model Reference Adaptive System). The second estimator, based on the estimation of the Back Electromotive Force (BEMF) of induction motor, is called Phase Locked Loop (PLL). A method of estimating the speed of an Induction Motor is proposed, analyzed and experimentally verified. DSPic based SVM controlled three phase inverter fed Induction Motor drive has been designed and implemented.