A new pulse active width modulation for multilevel converters

This paper proposes a new pulse amplitude width modulation (PAWM) procedure for cascaded H-bridges multilevel inverters fed by DC voltage sources with unequal amplitudes. With proposed procedure, the generated output voltage is obtained modulating a sinusoidal reference signal at the desired fundamental frequency with equally spaced switching angles. It has been analytically demonstrated that, under these assumptions, all harmonics except those of order n=2kl$pm$1, k=1, 2, … are deleted from the output voltage waveform. After a detailed description of the method and a comparative analysis with others existing in literature, its harmonics elimination capability has been experimentally verified with 5, 7, 9 and 11 level cascaded H-bridge inverters, moreover it has been mathematically demonstrated that it reduces THD below 5% with a 17-level inverter and it is capable to eliminate the first 49 harmonics considered by standards with a 27-level inverter.