Coordinated‐control strategy of scalable superconducting magnetic energy storage under an unbalanced voltage condition.

Modular multilevel converters (MMCs) have the advantages of high‐power density and small‐harmonic distortion because of their modularity and flexibility, thus providing a new avenue for research into scalable superconducting magnetic energy storage (SMES) in renewable energy generation. This study presents coordinated control for a three‐phase four‐wire (3P4W) MMC‐based SMES system under unbalanced voltage applications. First, the positive‐ and negative‐sequence mathematical models and the port‐controlled Hamiltonian with dissipation model of the 3P4W MMC‐SMES system are established by introducing an additional path for zero‐sequence current. Second, a multi‐objective passivity‐based control strategy that can effectively improve the power quality and system robustness and eliminate both double‐frequency active and reactive power fluctuations or double‐frequency active power fluctuation and negative‐sequence current is proposed. The simulation results based on MATLAB/Simulink demonstrate the effectiveness of the proposed topology of the SMES and its control strategy. [ABSTRACT FROM AUTHOR]