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Acoustic Noise and Its Control in SRMs
Published in R. Krishnan, Switched Reluctance Motor Drives, 2017
Modulation of phase voltages while varying switching frequency or the pulse position randomly is referred to as random pulse width modulation (RPWM). A number of publications have established that RPWM causes the power spectrum of the output voltage to acquire a continuous part, while the harmonic part is significantly reduced, which in turn reduces very marginally acoustic noise and vibrations while the sound pressure is not affected.22 This strategy has been applied to induction motor drives, and a few attempts have been made to adapt it to SRM drives.21,23,24
Dual randomized discontinuous pulse width modulation for three-phase inverter
Published in International Journal of Electronics, 2023
Nowadays, the use of three-phase voltage source inverters (VSI) occupies a very important place in energy conversion (UPS, renewable energies, variable speed drives, etc.). Pulse-width modulation (PWM) is a key element in the voltage source inverter’s control; it allows adjusting the useful voltage component and eliminates some undesirable harmonics (Boudjerda et al., 2014). Inverters are generally operated at a fixed switching frequency, resulting in harmonic clusters in the voltage and current spectrum at multiples of the switching frequency, causing electromagnetic interference (EMI) emissions, serious switch noise, and audible noise in variable speed drives (Li et al., 2021; Pan et al., 2018). Increasing the PWM’s switching frequency can reduce switch and audible noise, but it also increases the inverter’s emitted emissions and switching losses (Pan et al., 2018). In recent years, random pulse width modulation (RPWM) has become a feasible substitute for traditional PWM. RPWM disperses the harmonic components across a smooth and low-amplitude noise spectrum, without raising the switching frequency (Boudouda, Boudjerda, et al., 2022). It has a number of advantages, including enhancing conformance with EMC standards for EMI and mitigating audible noise in variable speed drives (Boudouda, Boudjerda, et al., 2022; Lezynski, 2018; Li et al., 2021; Mihali & Kos, 2006). Existing basic random schemes with a single random parameter are randomised carrier frequency modulation (RCFM) and randomised pulse position modulation (RPPM) (Boudjerda et al., 2014; Kirlin et al., 2002; Li et al., 2021; Mihali & Kos, 2006; Moon et al., 2021; Pan et al., 2018; Zhang et al., 2020). However, a combination of the two schemes (RCFM-RPPM) has also been proposed for maximising the voltage spectrum spreading (Boudouda, Boudjerda, et al., 2022; Boudouda et al., 2016,2018; Bu et al., 2019; Drissi et al., 2003; Huang et al., 2019; K. S. Kim et al., 2009). In addition, an optimised version of the dual-randomised scheme is studied (Boudjerda et al., 2014). It has been shown that the optimised dual-randomised scheme gives the best spread spectrum of the voltage relative to simple schemes.