Multi-carrier pulse width modulation schemes for multilevel converters

21-level 3-phase cascaded h-bridge multi-level inverter with different multi-carrier level shift pwm techniques and their thd analysis

“…They are classified basically based on the placement of various carrier signals [3]. For generation of n level, n-1 carrier signals are required.…”

“…For generation of n level, n-1 carrier signals are required. For generation of 21 level, 21-1=20 carrier signals areRequired The MCLS-PWM methods are used in the controlling of inverters where power balancing is not required [3]. Here all the multi-carrier level-shifted PWM techniques are shown for R-phase.…”

“…In case of POD-PWM technique, the carrier signals above the zero axes and below the zero axes are 180° out of phase but the carriers above the zero axes or positive carrier signals are in same phase and the carriers below the zero axes or negative carrier signals are in same phase [3].…”

“…each carrier of this method is phase shifted by 180 degrees from its adjacent carrier [3]. Below fig.4 shows the one phase (R-PHASE) arrangement of reference and carrier waveforms to generate switching pulses for the 21-level cascaded multi-level inverter for APOD-PWM technique.…”

“…The pure sinusoidal signal used with carrier signals is known as SPWM, & is illustrated in below fig.5 [3]. Likewise threephase sine-wave modulation signals are generated with their respective phase-shifts i.e.…”