Modified single-carrier multilevel sinusoidal pulse width modulation for asymmetrical insulated gate bipolar transistor-clamped grid-connected inverter

Conventional sinusoidal pulse width modulation (SPWM) for single-phase asymmetrical seven-level insulated gate bipolar transistor (IGBT)-clamped grid-connected inverter (IC-GCI) needs an additional logic operation circuit and a dead zone generation circuit, which raises cost and complicates the implementation. In addition, both added circuitries decrease the reliability. In this study, a modified single-carrier multilevel SPWM (MSCM-SPWM) scheme suitable for IC-GCI is proposed. By setting one carrier, three digital signals to identify voltage zones and six equivalent modulation waves, the control signals of the switches in IC-GCI can be generated with only one digital signal processor controller and simple logic operation. It makes the implementation of the multilevel GCI easier. The detailed spectral character of the MSCM-SPWM is originally derived based on double-Fourier integral theory and then compared with the conventional scheme. It proves that they own the similar spectral character. Detailed simulation and experimental results verify the accuracy and feasibility of the MSCM-SPWM and the single-phase IC-GCI.