Evaluation Methods for Incorporating Non-Deterministic Characteristics in PWM Strategy of Induction Motor Drives and FPGA Based Experimental Implementation
Dr. S.R. BOSELIN PRABHU Dr. T.JARIN
The primary advantages of non-deterministic pulse width modulation (PWM) strategies are that the harmonic power in the output voltage is spreaded over wider range in the frequency spectrum and does not get grouped at definite frequencies. This absence of distinct dominant harmonics results generally in reduction of acoustic noise and torque ripples in the drives. The effectiveness in acoustic noise reduction is contingent on how efficiently the non-deterministic characteristics (randomness) are being incorporated in the PWM strategy. This paper proposes two dissimilar approaches to integrate the randomness in the PWM suitable for induction motor drive. Primarily, a Pseudo Random Binary Sequence (PRBS) bit based random carrier PWM (RCPWM) is deliberated. Then, a comprehensive investigation of performance of random pulse position pulse width modulation (RPPPWM) is worked out. A comprehensive simulation study on performance characteristics such as harmonic spectrum, total harmonic distortion (THD), harmonic spread factor (HSF) and power density spectrum, are presented for conventional sinusoidal PWM (SPWM), RCPWM and RPPPWM. The results are validated through the prototype VSI designed. The implemented pulse width modulators using a SPARTAN-6 field programmable gate array (FPGA) (XC6SLX45) device corroborate the simulation study and hint the triumphing one.
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