부산대학교 도서관

Active neutral point-clamped (ANPC) multilevel converters with integrated flying-capacitor (FC) technique are widely used in many industrial applications owing to their low losses, reduced stress on devices, bidirectional operation, and leakage current attenuation capability. Their major setback related to the half dc-link voltage utilization at the ac output has also recently been addressed using the concept of active boost neutral point-clamped (ABNPC) converters with a switched-capacitor (SC) technique. Nonetheless, such a voltage-boosting capability in ABNPCs causes an excessive voltage stress on devices, when the provided dc-link voltage is larger than double of the grid peak voltage. To address this critical challenge, the concept of dual-mode (DM) converter that can retain the quality of ac output with a reduced voltage stress on devices over a wide range of the input dc voltage is introduced. Following this concept, a family of three DM-ANPC five-level (5L) converters is presented in this article, where they can be operated in either buck or boost mode. This allows to operate the converters with a wide range of input dc voltage utilization and an improved performance. Each of the proposed DM-ANPC-5L converters requires 10 power switches, while they offer a bidirectional power flow feature with an integrated FC and/or SC technique. Extensive analysis, comparative study, and several simulation and experimental results obtained from a laboratory-built prototype operating in the grid-connected condition are presented to validate the performance of the proposed converters.