Minimization of THD for Multilevel Converters with triangular injection approach

Cascaded H-Bridge Converter (CHBC) has become popular for medium power applications which composed with array of DC sources but for not having inherent redundancy with non-modular topologies and series connection of switches in order to cope with the high DC-link voltage, increasing the converter's control complexity. Modular Multilevel Converter (MMC) can be used to avoid this problems, additionally allowing to save cost as large quantities of modules and components are required. Carrier based modulation are very popular for Modular Multilevel Converter (MMC) among all proposed modulation methods. Nowadays, the center of research focuses on to achieve lower minimize Total Harmonic Distortion (THD) of the converter's output. Harmonic profile of a converter with a modulation scheme much depends on the carrier frequency used in it. This paper proposes a modulation structure for both CHBC and MMC converters to maintain minimum harmonic profile in case of wide range of carrier frequency, and to improve the output voltage quality of the converter. Some well-known modulation methods are compared with proposed method so that percentage of THD can be identified as minimum and quality of the output voltage is better. The MATLAB simulation results show that converters have lower THD in compare to typical modulation.