HVDC Systems: Architectures, Modeling, Control & Simulation

In recent years, the power engineering community has focused on high voltage direct current (HVDC) grids, essential for carbon-neutral energy systems that utilize remote renewable energy sources. Several factors drive this interest. Energy markets increasingly demand electricity trade over long distances, and HVDC offers lower per-kilometer costs than HVAC. Moreover, HVDC avoids reactive power and skin effects, reducing transmission losses and improving efficiency. It also connects unsynchronized AC systems and enhances the stability grids. Modeling, control, and simulation play crucial roles in developing HVDC systems. During design, simulations help anticipate risks and ensure cost-effective implementation. During commissioning and operation, precise modeling fine-tunes system performance. However, existing tools like MATLAB and DIgSILENT PowerFactory have limitations, being proprietary and lacking transparency in the models. This has prompted the European Network of Transmission System Operators for Electricity (ENTSO-E) to encourage standardized approaches using open-source tools like Modelica, which offers an equation-based language, making it ideal for power system modeling and reuse. However, current Modelica-based HVDC libraries often lack comprehensive modeling, focusing only on voltage source converter (VSC)-HVDC systems and neglecting line-commutated converter (LCC)-HVDC systems and detailed switching behavior. To address this, we propose a Modelica-based framework for reusable, transparent HVDC models, covering both VSC and LCC systems, including power electronics details and control strategies. We will validate these models against MATLAB/Simulink simulations to ensure accuracy.