Superconducting magnetic energy storage based modular interline dynamic voltage restorer for renewable-based MTDC network

Multi-terminal DC distribution network is regarded as a promising solution to integrate DC loads, energy storages, and renewable generators with different voltage and current levels. However, the rapid over-current variation, large over-current magnitude, and widespread use of power switches make it difficult to ride through the power quality issues including DC voltage sags, swells, as well as second-order voltage ripples. To strengthen the fault ride-through capability, superconducting magnetic energy storage (SMES) and series-connected custom devices are expected as promising solutions. This paper proposes a SMES-based modular interline dynamic voltage restorer (MIDVR) for multi-line DC device protections. It is mainly comprised of N modular converters to realize the voltage sag and swell compensation capabilities and the second-order voltage ripple suppression, where all the modular converters share one power-supplying SMES. The working principle, control strategy, capacity estimation, and universal extension methodology of the SMES-MIDVR concept are presented and technically verified by a MW-class edge-data-center-based DC simulation network. A kW-class experimental SMES prototype is established and tested to prove the feasibility and practicability of the SMES-MIDVR. Finally, the techno-economic analysis shows that the static and dynamic payback periods are only 7.82 and 16.13 years in IDC damage ratio is 0.175, which proves the SMES-MIDVR has both technical and economic advantages in renewable-based multi-terminal DC distribution network. •A novel topology of superconducting magnetic energy storage (SMES) based modular interline dynamic voltage restorer (MIDVR).•SMES-MIDVR can share one SMES unit and protect multiple loads with different voltage and current levels.•A kW-class prototype is verified for its well-suppression capabilities of voltage sags, swells, and second-order ripples.•Varying-axial-gap optimization of magnet structure enhances 44.5% the SMES capacity.•SMES-MIDVR has both technical and economic benefits for multi-terminal DC distribution network protection.