"Hybrid PWM Algorithm based Direct Torque Controlled Induction Motor Drive for reduction of ripples and Harmonic Distortion"


P. Nagasekhara Reddy
Department of Electrical and Electronics Engineering Mahatma Gandhi Institute of Technology, Hyderabad, Telangana, India.


The conventional SVPWM algorithm gives good performance for control of induction motor drive, but it produces more acoustical noise resulting in increased total harmonics distortion. The random pulse width modulation (RPWM) techniques have become an established means for mitigation of undesirable side effects in adjustable speed ac drives in particular. The conventional PWM inverters generate high harmonic content and concentrated power spectrum. Using RPWM techniques the harmonic spectrum of inverter is continuously distributed, and thus, the harmonic content in the current waveform is reduced, resulting reduction of ripple in electro-magnetic torque. This paper presents a novel hybrid pulse width modulation (HPWM) technique for the reduction of common mode voltage (CMV) in direct torque controlled induction motor drives based on the concept of imaginary switching times. In the proposed approach, different active zero state PWM sequences are considered in which the actual switching times are calculated based on the instantaneous values of phase voltages. So, it does not require sector identification and angle information. The simulation results of the DTC of IM drive proves the effectiveness of RPWM techniques in the reduction of the ripple and harmonic distortions.