WTHD-optimal staircase modulation of single-phase multilevel inverters

This paper considers the problem of achieving the minimum frequency-weighted THD of the output voltage of multilevel inverters, when staircase modulation is utilized. Since the single-phase AC case is being addressed, the triplen harmonics need to be included in the analysis. The results show that using unequal, non-integer ratio, DC source voltages is significantly better than using equal ones, as expected. They also indicate that imposing the requirement of eliminating the lowest harmonics leads to slightly worse distortion than the minimum that is achievable