Simulation and experimental verification of modified sinusoidal pulse width modulation technique for torque ripple attenuation in Brushless DC motor drive

Abstract

The Brushless DC motor when operated with120° conduction mode with quasi square wave current in phase with trapezoid back emf leads to finite torque ripple in the commutation region with only two phases conducting at any time. To overcome this, the BLDC motor phases can be supplied with sinusoidal currents which reduce the voltage required to deal with the phase inductance instead of quasi square currents as the change in currents is smoother because of its shape. The proposed technique aims to develop closed-loop speed control of BLDC motor using Modified Sinusoidal Pulse Width modulation (MSPWM) technique by providing sinusoidal stator currents in synchronism with the trapezoid back emf to reduce the commutation torque ripple with improved dynamic performance. The closed-loop control is accomplished by providing a PI controller for a speed control loop. Hall sensors along with shaft encoder are used for detecting the accurate rotor position and speed. This technique provides a higher DC bus utilization as compared to conventional six-step control with torque ripple reduced up to 50%. To justify it, simulation is performed using MATLAB®/SIMULINK at different speed and load. The experimental verification is carried on a prototype using the STM32F407VG microcontroller with Cortex-M4 32 bit ARM controller. The experimental results validates the closed-loop speed control operation of BLDC motor using MSPWM technique.