Comparative Analysis and Optimal Design of Interleaved Versus Classical Modular Multilevel Converters in Power Transmission and Distribution

Modular Multilevel Converter with Interleaved Half-Bridge Submodules (ISM-MMC) has the potential to emerge as a new apparatus for power transmission and distribution due to offering expanded current and improved power quality. However, the applicability of converters depends on various factors, there is a lack of quantitative methods for assessing the economy and reliability of ISM-MMC. The appropriate topology between classical MMC and ISM-MMC remains elusive, and relevant design is also a challenge. To address these issues, this paper presents a design method for ISM-MMC that integrates cost, efficiency, and reliability to provide a basis for engineering applications. Classical MMC can be considered as a special case of ISM-MMC. By combining the topological structure and operational characteristics, analytical representation functions for cost, efficiency, and reliability are derived respectively. On this basis, a parameter optimization method is established, that can also provide a selection guideline between the two topologies. By rationally configuring parameters such as switch ratings and modularity, a balance between cost, reliability, and efficiency can be achieved. Simulation case studies show that ISM-MMC is suitable for high-current applications, and the optimal modularity of interleaving is 2–3. The insights from this paper are extended to provide a general design guideline.