Research On Overvoltage Suppression Of HTS SMES Considering Voltage Distribution Characteristics

Superconducting Magnetic Energy Storage(SMES)has the advantages of fast response speed,large energy storage density and low loss,which is suitable for dynamic power compensation of power systems.During operation,the superconducting magnet exchanges power with the AC grid through the power conditioning system(PCS).The PCS generally adopts a PWM converter based on a high-frequency switching device,and its output PWM pulse voltage with a steep rising / falling edge is transmitted to the superconducting magnet through a cable and a current lead.A peak overvoltage is generated at the terminal of the superconducting magnet,which in turn causes the voltage distribution inside the magnet winding to become uneven,threatening the safety of the magnet operation.In this paper,when the SMES magnet is subjected to high-frequency PWM pulse voltage,simulations and experiments were conducted on the overvoltage distribution characteristics in the superconducting magnet.From the perspective of optimizing magnet parameters and increasing filtering topology,the method of suppressing SMES magnet overvoltage was studied.The main work completed in this article is as follows:(1)The transient model of high-temperature superconducting magnet is studied,and the frequency domain analysis method of magnet voltage distribution characteristics is proposed.Based on the existing conditions in the laboratory,the voltage distribution characteristics experiment was designed and completed,and the accuracy of frequency domain analysis of the voltage distribution characteristics of superconducting magnets was verified.On this basis,by analyzing the amplitude-frequency characteristics of the magnet through the frequency domain model,the resonance frequency band of the magnet can be obtained,which is used to guide the selection of the switching frequency of the converter.(2)The relationship between SMES magnet parameters and voltage distribution characteristics is studied.Through the analysis of voltage distribution characteristics under different variables,the optimization design method of magnet parameters to reduce the unevenness of voltage distribution is explored.The design scheme of 3.8MJ SMES in a microgrid was corrected and modified,and the feasibility of the optimized design of magnet parameters was verified.(3)On the basis of the catadioptric reflection of the voltage wave between the converter,cable,and superconducting magnet,the influencing factors of the overvoltage peak at the magnet end are studied.The RC filter and RLC filter are designed to suppress the transient overvoltage.Simulation analysis verified its feasibility.