Improvement of torque undulation in BLDC using SEPIC and common end diode clamped three-level inverter

Brushless Direct Current Motor (BLDC) is extensively used in medium and high-power applications for robust construction and flexibility in operation. The commutation of BLDC motor in the high-speed region provides torque undulation in three-level inverter systems. This paper presents an improved converter method for minimizing the torque undulation in BLDC motor for three-level systems using the trapezoidal back Electromotive Force (emf) method. To regulate constant voltage improved Single-Ended Primary Inductor Converter (SEPIC) is used and further to reduce torque undulation, the 3-Level Common End Diode Clamped inverter (3-LCEDCI) is designed into the scheduled circuit. Experimental validation of BLDC motor for a switching frequency of 5 KHz using 3-LCEDCI maintains constant speed for variation in load. Fuzzy based BLDC motor is used further to improve the torque undulation for various switching frequencies. The execution of the scheduled approach is simulated using MATLAB/Simulink under closed-loop operation and compared with the experimental setup to validate the speed for various switching frequencies.