Systematic and optimal design of droop-controlled MMCs in MT-HVDC networks

Multi-terminal High-Voltage Direct-Current (MT-HVDC) Voltage Source Converter (VSC) based grids are arising as an extension of point-to-point connections, aiming at boosting the integration of renewable energy resources through a more interconnected power system. This paper investigates and compares different energy-based control structures for Modular Multilevel Converters (MMC) operating in DC voltage droop control mode, identifying the most suitable ones in terms of stability. Then, a systematic, automatic and optimal control design based on H∞ for a generic and bidirectional MT-HVDC system, including multiple DC voltage droop controlled terminals, is developed, based on both steady-state and transient requirements under different contingencies. •DC voltage droop control structures comparison for MMCs in multi-terminal HVDC networks.•Systematic optimal control tuning method based on H∞.•Combination of steady-state and transient requirements.•Converters with different power ratings and bidirectional operation (generation, load).