The Need
High-voltage DC (HVDC) transmission and grid-connected power conversion systems face significant cost, size, and efficiency challenges due to the large number of expensive submodules and capacitors required in conventional modular multilevel converters (MMC). These limitations restrict scalability, increase lifecycle costs, and complicate integration with renewable energy, energy storage, and advanced motor drive applications.

The Technology
This technology, developed by OSU engineers, introduces a novel Modular Multilevel Flying Capacitor (MMFC) converter that integrates flying capacitor and MMC architectures. By reducing voltage stress on converter arms to half the full DC voltage, the MMFC halves the required number of submodules and associated components. The converter’s unique topology enables fundamental frequency switching for key devices, minimizing losses and simplifying control, while maintaining compatibility with various submodule types and modulation schemes.

Commercial Applications
• HVDC power transmission and station infrastructure
• Asynchronous AC/DC grid interconnection
• Renewable energy integration (solar, wind, battery storage)
• Industrial motor drives and electric vehicle charging systems

Benefits/Advantages
• Up to 50% reduction in submodule count, cost, and system weight
• 1.15-fold reduction in power loss and improved efficiency
• Lower total capacitance and installation power capacity
• Smaller physical footprint and simplified control compared to conventional MMCs