Abstract
This paper proposes an enhanced modular multilevel converter as an alternative to the conventional half-bridge modular multilevel converter that employs a reduced number of medium-voltage cells, with the aim of improving waveforms quality in its AC and DC sides. Each enhanced modular multilevel converter arm consists of high-voltage and low-voltage chain-links. The enhanced modular multilevel converter uses the high-voltage chain-links based on medium-voltage half-bridge cells to synthesize the fundamental voltage using nearest level modulation. Although the low-voltage chain-links filter out the voltage harmonics from the voltage generated by the high-voltage chain-links, which are rough and stepped approximations of the fundamental voltage, the enhanced modular multilevel converter uses the nested multilevel concept to dramatically increase the number of voltage levels per phase compared to half-bridge modular multilevel converter. The aforementioned improvements are achieved at the cost of a small increase in semiconductor losses. Detailed simulations conducted in EMPT-RV and experimental results confirm the validity of the proposed converter.
Highlights
Half- and full-bridge modular multilevel converters (HB-MMC and FB-MMC, respectively) provide solutions for connection and reinforcement of weak AC networks [1,2,3]
This paper presented the Enhanced Modular Multilevel Converter to address some of the shortcomings of the conventional HB-MMC with reduced number of medium-voltage cells, its relatively poor ac and dc side power quality
It has been shown that the EMMC has potential to reduce the power circuit complexity of the full-scale HB-MMC, which is extremely important from condition monitoring and protection of high value assets such as HVDC converters
Summary
Half- and full-bridge modular multilevel converters (HB-MMC and FB-MMC, respectively) provide solutions for connection and reinforcement of weak AC networks [1,2,3]. The second approach employs a reduced number of medium-voltage (MV) cells per arm, in which each cell is typically rated for n (16–20) kV [9] This approach requires series connection of press-pack insulated gate bipolar transistors (IGBTs), with safe short circuit mode. Asymmetrical cells permit controlled operation of multilevel converters for a wide range of positive input dc link voltages, from rated to zero, including control of dc fault current and dc fault blocking. The introduction of few FB cells into the EMMC arms has helped to reduce the errors in the synthesis of the common and differential mode voltages In this way, the EMMC matches the performance of the HB-MMC that employs large number cells, which is achieved by small modifications to the power circuit of the HB-MMC that uses reduced number of MV cells.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
