Optimal Selective Harmonic Mitigation Technique on Variable DC Link Cascaded H-Bridge Converter to Meet Power Quality Standards

In this paper, the power quality standards such as IEC 61000-3-6, IEC 61000-2-12, EN 50160, and CIGRE WG 36-05 are fulfilled for single- and three-phase medium voltage applications by using Selective Harmonic Mitigation-PWM (SHM-PWM) in a Cascaded H-Bridge (CHB) converter. Furthermore, the ER G5/4 power quality standard, which has the strictest grid codes at medium voltage level, will also be met in the whole range of the modulation indices. In order to achieve this goal, symmetrical CHB with variable DC Links are employed, while the converter has a low number of switching transitions. In other words, all of the DC link voltages have the same voltage, which is dependent on the modulation index. Finally, in order to validate the effectiveness and the applicability of the proposed method, it is verified by simulations and experiments for a 7-level CHB converter.