RANDOM DISCONTINUOUS PWM SCHEMES FOR VSI FED AC DRIVE FOR REDUCTION OF HARMONIC DISTORTION, SWITCHING LOS S AND ACCOUSTIC NOISE

This paper presents space vector based random discontinuous PWM techniques for two level three phase inverter fed induction motor drive. The pulse width modulation (PWM) based induction motor drives often produces objectionable acoustic noise apart from harmonic distortion. The proposed modulation te chniques not only concentrate on harmonic reduction through reduced switching but also aim at acoustic noise reduction which causes inconvenience in certain applications such as electric propulsion for the drivers and passengers. The proposed algorithm is developed by using the imaginary switching times, which does not require angle and sector information. In order to get the randomization effect, the proposed algorithm uses discontinuous pulse width modulation algorithm in conjunction with the variable del ay pulse width modulation (VDRPWM) algorithm. The proposed PWM algorithm uses 012 and 721 sequences results 33.33% reduction in inverter switching loss, as the zero state time is varied randomly according to the operating sequence, randomization effect wil l occur, which results in reduced total harmonics distortion and hence gives reduced acoustical noise. To validate the proposed PWM algorithm, the numerical simulation studies have been carried out and results are presented and compared. The simulation res ults confirm the effectiveness of the proposed algorithm.