Multi-Port Modular Multilevel Converter Technology for Next-Generation High-Voltage DC Transmission
This invention introduces a novel Multi-Port and Multi-Terminal Modular Multilevel Converter (MPT-MMC) architecture capable of coupling three or more AC or DC power grids within a single, highly compact converter station. By replacing today's conventional two-port systems with a unified multi-port design, it dramatically reduces cost, physical footprint, and deployment complexity while enabling superior power flow control and grid resilience.
Description
Traditional Modular Multilevel Converters (MMCs) are limited to point-to-point conversion between one AC port and one DC port, requiring separate converter stations and substantial hardware to achieve multi-terminal connectivity. The MPT-MMC architecture breaks this constraint by combining multiple ports — three or more AC and/or DC connections — into a single converter station with as few as nine arms, compared to twelve or more in conventional bipolar configurations. This structural innovation reduces transformer requirements, lowers conduction losses, and decreases the DC capacitance needed per submodule. A key feature of the MPT-MMC is its ability to exercise fully independent, millisecond-scale power flow control among all connected ports by coordinating the controllable voltage sources within each arm group. Additionally, the architecture supports flexible dynamic grounding — the ability to instantly generate a virtual zero-potential reference within the converter — enabling fault currents on any DC line to be suppressed immediately without disrupting the rest of the grid. The technology is also designed to repurpose existing overhead AC transmission corridors as DC lines, dramatically lowering infrastructure costs and deployment timelines.Applications
- Offshore wind and renewable energy integration requiring flexible, multi-source DC collection and onshore interconnection- Hybrid AC/DC transmission grids where existing overhead line corridors are converted to higher-capacity DC links
- Multi-terminal meshed DC grids for large-scale regional power balancing and cross-border interconnection
- Industrial and utility-scale microgrids requiring compact, resilient DC power management across multiple sources and loads
- Urban and underground medium-voltage DC distribution networks where space and reliability are critical constraints
Advantages
- Compact multi-port station design with more than one-third reduction in converter arms versus conventional bipolar solutions- Full, independent power routing among multiple AC and DC ports within milliseconds — without additional DC-DC converters
- Instant dynamic grounding for DC fault clearance, enabling the highest possible grid resiliency and uninterrupted operation
- Ability to reuse existing single- and double-circuit AC transmission infrastructure for DC conversion, lowering capital costs and right-of-way requirements
- Targeted cost, footprint, and volume reduction of three times or more compared to current HVDC converter station benchmarks