Md Nazmul Hassan Chowdhury, a Ph.D. student in Rensselaer Polytechnic Institute’s Douglas A. Mercer ’77 Department of Electrical, Computer, and Systems Engineering (ECSE), received the Best Student Paper Award at the 2026 American Modelica & FMI Conference, held October 12–14, 2026, at the Georgia Institute of Technology in Atlanta.
The paper, titled “MMChvdcLibrary: Modeling Arm Average Value Modular Multilevel Converters in Modelica for Power System Simulation,” was co-authored by Chowdhury and his doctoral advisor, Professor Luigi Vanfretti, who leads the ALSET Lab at RPI. The award was presented by Conference Co-Chair Dr. Hubertus Tummescheit (Model Based Innovation LLC) and Program Co-Chair Dr. Michael Wetter (Lawrence Berkeley National Laboratory).
Converter Models for HVDC Transmission
High-voltage direct current (HVDC) links are increasingly used to bring offshore wind power to shore and to interconnect power grids, and the modular multilevel converter (MMC) has become the reference converter design for modern HVDC links. Detailed electromagnetic transient models of MMCs reproduce every switching event, but their computational cost limits their use in studies of large power systems with many generators, buses and HVDC terminals.
The award-winning paper presents MMChvdcLibrary, an open-source Modelica library for phasor-domain arm average value modeling of MMC-based HVDC systems. In an arm average value model, the stack of submodules in each converter arm is replaced by an equivalent controlled source and capacitor. The model keeps the converter’s internal energy dynamics without representing individual switching events, which makes it suited to system-level stability studies at a lower computational cost.
The library provides converter models, control blocks and measurement components, assembled into ready-to-use HVDC station models for three operating modes: active and reactive power control; DC voltage and reactive power control; and AC voltage control for supplying passive or islanded networks, such as offshore wind farms. A configurable master station model combines all three modes in a single component. The library is compatible with OpenIPSL, the open-source power system library maintained by the ALSET Lab, and is freely available on GitHub under the BSD 3-Clause license.
The work was supported in part by the New York Independent System Operator (NYISO) through the project “Dynamic Modeling of Voltage Source Converters for Black Start Capability Analysis.”
Building on the ALSET Lab’s HVDC Research
The paper builds on the ALSET Lab’s research on HVDC and converter modeling with open standards. In 2025, Elia Group and Energinet selected Professor Vanfretti’s team, the only U.S.-based team, to respond to their Open Research Challenge. In that project, completed in August 2026, the team re-engineered manufacturers’ black-box HVDC models as simplified white-box models using the Modelica and FMI open standards, giving grid operators an alternative to proprietary vendor models.
“Congratulations to Nazmul on this well-deserved recognition,” said Professor Vanfretti. “Grid operators increasingly need HVDC converter models that are transparent and can be exchanged between simulation tools. Nazmul’s work addresses this need using open modeling standards.”
“I am honored to receive this recognition from the American Modelica & FMI Conference. I am especially grateful to Professor Luigi Vanfretti for his guidance and continued support throughout this work. He has pushed me to go further, and this achievement would not have been possible without his mentorship. I would also like to thank the conference organizers for recognizing our work,” said Chowdhury. “I hope MMChvdcLibrary will be useful to others who model HVDC systems.”
The American Modelica & FMI Conference is organized by the North American Modelica Users Group (NAMUG) in cooperation with the Modelica Association. This year’s edition was hosted by Georgia Tech’s Aerospace Systems Design Laboratory and brought together researchers and engineers from industry, national laboratories and academia who use Modelica and FMI for modeling and simulation.
Read the paper: ResearchGate
Download the library: GitHub — ALSETLab/MMChvdcLibrary
Conference website: American Modelica & FMI Conference 2026