DC-link regulation of a multilevel asymmetric cascaded D-STATCOM with staircase and discontinuous PWM modulation

Recently, problems related to poor energy quality, which in the last decade were responsible only for annoying situations and small losses in low voltage systems, are now causing damage to equipments and high financial losses to industries in medium voltage systems. The recent necessity of a better energy quality encourages the development of new specific custom power equipments directly connected in medium voltage systems. Therefore, several solutions were applied in order to enable the connection of custom power equipments in the medium voltage system, like as step down transformers and series connected semiconductors. However, it is well know that the multilevel converters are perfectly capable to work directly in the medium voltage systems and also presents several advantages when compared with others solutions. Although, some topologies, like the asymmetric cascaded multilevel converter, presents difficulties in regulating all the separated dc-link capacitors. In this context, this article presents a multilevel D-STATCOM with a proposed dc-link regulation control loop for generic cascaded multilevel converters to work directly in the medium voltage systems in order to improve the power quality in industrial installations. The performance of the multilevel D-STATCOM is presented by simulation and experimental results.