SHE formulation for five level inverters with unequal DC sources

Because of their numerous advantages including high voltage operations and limited harmonics content, multilevel inverters are often used in high power applications. However, dc sources supplying the inverter do not always have the same voltage, thus resulting voltage unbalances and performance deterioration. In order to solve such a problem, this paper proposes a modulation technique based on a harmonic elimination method developed for five level inverters with unequal dc link voltages. The approach is based on the analytical solution of non linear equations associated with the inverter. After a description of the method, an analysis on the computed switching angles and on their impact on total harmonic distortion is reported with the support of simulation results.