Design and lifetime analysis of a DSCC-MMC STATCOM

The modular multilevel converters (MMCs) has been employed in several applications as HVDC systems, energy storage, renewable energy, electrical drives and STATCOMs. In STATCOM application, the converter needs to compensate negative sequence components and unbalanced currents. Nevertheless, the design proposed in the literature considers only positive sequence compensation. Since the STATCOM is submitted to a variety of current stresses, the reliability analysis is strongly recommended. Therefore this work presents a lifetime analysis and a design methodology considering both positive and negative sequence reactive power compensation. A case study considering a 7 MVA MMC STATCOM is analyzed in order to validate the proposed design. The lifetime consumption of the power modules employed is evaluated considering a mission profile acquired from a factory in southeastern of Brazil. Two IGBT solutions (with different current rating) are compared. The results indicate that doubling the power modules rated current increase the initial cost less than 60%, on the other hand, the converter lifetime can increase until 3.6 times and the losses are reduced in 4.4%.