The Effects of PDFs on the Line-to-Line Voltage and Noise Generated by PWM Inverters

Abstract- Acoustic noise is a drawback of PulseWidth Modulated (PWM) inverters switching at frequencies within the audible range. This drawback becomes an important concern when the PWM inverter is located in the vicinity of people (e.g., industrial sites, HVAC installations, etc.). Increasing the switching frequency beyond the audible range is a possible solution that unfortunately leads to the derating of the PWM inverter. On the other hand, random PWM techniques are economical alternatives for acoustic noise reduction. To this end, this paper firstly addresses the development of a random space vector PWM algorithm making use of a small number of switching frequencies (i.e., a limited pool). The random PWM algorithm controls the speed of an induction motor (IM) driven under the constant V/Hz principle. Then, this paper compares the impact that different well-known Probability Density Functions (PDFs) assigned to the switching frequencies in the limited pool have upon the line-to-line voltage waveform and acoustic noise. The PDFs are implemented in a TI TMS320C240 fixed-point digital signal processor (DSP) that is used to control a three-phase IM. I