Selective Harmonic Elimination in Multimodule Three-Phase Current-Source Converters

Modular current-source converter (MCSC) structures can enhance the current capacity and improve the power quality of converters in medium-voltage pulsewidth-modulated applications. An MCSC uses individual three-phase modules in a shunt connection to share the total power in a symmetrical manner. The modulation of these units is normally done using optimized patterns such as selective harmonic elimination patterns. However, the optimization is usually performed at the module level. This paper proposes a modulation technique that optimizes the operation of a complete MCSC taking into account all P modules. Thus, from the injected ac current, we remove P times the number of harmonics as compared with the conventional approach using the same switching frequency. A complete mathematical formulation and experimental results validate the proposed approach.