Conceptual Design and Evaluation of an HTS Magnet for an SMES Used in Improving Transient Performance of a Grid-Connected PV System

This paper suggests a small-scale superconducting magnetic energy storage (SMES) to enhance the transient behaviors of a 100 kW grid-connected photovoltaic (PV) system, and conducts the conceptual design and performance evaluation. Considering the PV system requirements, the stored energy of the SMES is 90 kJ, and the YBCO tapes are adopted to make a solenoid SMES magnet. Based on the genetic algorithm, the magnet parameters including critical current, tape length, parallel and perpendicular magnetic fields are optimized. Using simulation tools, the effects of the SMES on the PV system are assessed, and the electromagnetic properties, stress, and loss of the SMES magnet are analyzed. The results prove that 1) the SMES improves the fault-ride-through capability and realizes an effective protection for the PV system. 2) A relatively large perpendicular magnetic field is found in both ends of the SMES magnet, and the maximum field is induced in the middle of the SMES magnet. 3) The maximum stress of the SMES magnet is acceptable, and the mechanical strength is satisfied. 4) The ac loss is crucial for voltage maintenance performance of the SMES at the fault. Under a short clearance time, the heat accumulation may have a moderate controllability.