Investigation of SMES-Battery Hybrid Energy Storage System for Robustness Enhancement of Solid-State Transformer

This paper studies a hybrid energy storage system (HESS) incorporating battery and superconducting magnetic energy storage (SMES) for the robustness increase of a solid-state transformer (SST), which conducts the voltage conversion and power exchange between different power networks. Firstly, the topological structure and control mode of the SST are stated. Then, to address the SST's voltage stability issue caused by power disturbances, a fuzzy control scheme is presented to adjust the power response of the HESS. Based on the differences in power time scale and charge/discharge behaviors, the proper power allocation law is obtained for the SMES and the battery. In addition, a schematic design of a 10 H/200 A SMES magnet is implemented. The parameters of the HTS magnet, encompassing critical current level, tape length, and magnetic field strength, are refined. Using the MATLAB platform, the performance validation of the SMES-battery in a 10 kV/ 1 kV SST is done. The simulation results affirm the credibility of the SMES-battery in maintaining the power balance and boosting the bus voltage stability of the SST under varying degrees of disturbance. The voltage fluctuations in the DC bus are effectively limited, and the DC voltage promptly returns to a steady state, while the state of charge (SoC) of the SMES-battery is within favorable levels.