Design and Analysis of Field Oriented Control of Permanent Magnet Brushless DC Motor

Abstract

This research project is about Field Oriented Control strategies for Permanent Magnet Brushless DC (PMBLDC) Motor. In PMBLDC Motor for Field Oriented Control direct axis reference current Id ref is considered zero, therefore forces the current space vector in the quadrature direction. Since only the quadrature axis current produces useful torque, this maximizes the torque efficiency of the system. Three PMBLDC Motor Control systems are designed, namely (1) Sinusoidal Current Regulated Pulse Width Modulation (CRPWM) Control, (2) Square Wave Current Regulated Pulse Width Modulation Control and (3) Voltage Regulated Space Vector Pulse Width Modulation Control. A state space model consisting three phase currents, three phase voltages, speed and position is developed. For testing, C++ simulation programs are designed for these three control strategies. The performance of the proposed control methods are studied for starting condition, load torque changes, speed variation, stator resistance changes and initial rotor angle mismatch condition. We have observed that Field Orientation Control methods have good performance and speed response. But speed response in Space Vector Pulse Width Modulation Control is better. Overall performance of all three control methods are proved satisfactory for speed control. A simple experiment is also done in the laboratory with a prototype design by using customized software in an electronic control board with integrated inverter. There is a built in position sensor embedded on the motor. The system was run in open loop and found to work satisfactorily.