New hybrid control methods based on multi-carrier PWM techniques and charge balance control methods for cascaded multilevel converters

In this paper, the elimination of low order harmonics in a cascaded multilevel converter by considering the charge balance control methods is proposed. Reduction of the total harmonics distortion (THD) and improvement of the harmonic spectrum of the output voltage are some advantages of the proposed hybrid control methods. Due to the use of the charge balance methods, the lifetime of the used dc voltage sources in the multilevel converter is equalized. As a result, the charging or substitution time of dc sources is reduced which leads to a reduction in the maintenance cost of converter. The operation and performances of the proposed control method have been verified by the simulation results of a single-phase 5-level converter using PSCAD/EMTDC software.