WTHD optimization for single phase multilevel converters with step modulation

This paper proposed a new approach for switching angle calculation to achieve the WTHD minimization of the output voltage for single phase multilevel converters with step modulation. The mathematical derivation for the switching angle calculation and the proof of the minimized WTHD are presented in detail. The switching angles of the converters can be selected from a pre-calculated look-up table, which is obtained by solving a set of nonlinear equations. The proposed method is compared with other switching angle calculation methods, and the results show that the proposed method always provides the minimized WTHD, which implies that it will minimize the harmonic content of the output current and the harmonic losses in the inductive loads of the system. Simulation results verify the proposed method.