Optimal Current Reference Calculation for MMCs Considering Converter Limitations

The paper addresses an optimization-based reference calculation method for Modular Multilevel Converters (MMC) operating in normal and constrained situations (when the converter needs to prioritize its quantities as it has reached voltage or current limitations, e.g. during system faults). optimization problem prioritizes satisfy external AC active reactive set-points demanded by grid operator through corresponding code. If demands are fulfilled, uses available MMC degrees of freedom minimize arm inductance losses. Otherwise, if cannot be accomplished, attempts error prioritizing between either currents. constraints imposed a steady-state model considering simultaneously internal DC magnitudes converter. also includes variation equivalent capacitors (considering ripple). Then, limitations maximum allowed currents, voltages sub-module capacitor voltages. presents detailed formulation applies several case studies where is shown that presented approach can potentially used obtain references both fault conditions.