Keywords: pulse width modulation, PWM, variable carrier frequency band, VFCB, varying amplitude carrier band, VACB, multi–level inverters, MLI, harmonic power
A novel invariable carrier frequency multi–level inverter PWM for balancing switching transitions and better distribution of harmonic power
The number of switching per modulation cycle at each level in a multi–level inverter depends on the carrier frequency and the duration that the reference waveform dwells within the level. The variable carrier frequency band (VFCB) approach creates as many clusters as the number of carrier frequencies and consequent deterioration of the harmonic spectrum. Therefore, a new pulse width modulation (PWM) strategy, with the view to ensure that the power devices at all the levels are switched equal number of times, is proposed in this paper. It is designed such that the frequency of the carrier waves is allowed to remain constant for the chosen application while maintaining the number of switching for all devices is same. The MATLAB–based simulation response and its experimental validation are included to highlight the fact that there is a significant enhancement in harmonic power distribution besides contributing to reduce the switching losses and improve the efficiency.