| The International Thermonuclear Experimental Reactor (ITER) program is of greatimportance to achieve controlled nuclear fusion and to solve the energy crisis of thehuman society, up to now, China, USA, European Union, Russia, Japan, Korea and Indiahave been involved in this program. ITER Poloidal Field (PF) converter power supplysystem procurement package is mainly borne by China. PF converter is power supply forITER poloidal magnet, which plays a crucial role in plasma shape control. Thus, thereliability and the safety of PF converter are very important for ITER. The main circuit ofPF converter is a typical twelve pulse thyristor rectifier, to guarantee the reliability and thesafety of the converter, the semiconductor switches must be protected effectively. Insemiconductor rectifier protection, three kinds of protection are usually combinedly used,they are electronic protection, fuse protection and circuit breaker protection. Fuseprotection is the primary protection of semiconductor switches. PF converter has highrated power and hundreds of thyristors in parallel, the structure is complex and its runningmode changes with time. Thus, high reliability is needed for the fuse protection.In this paper, the design of fuse protection and selection of fuse for high powerconverters are researched according to the characteristics of PF converter, combining withthe protection requirements.In this paper, a set of fuse protection design is put forward based on the basis of thefuse protection, IEC standards and engineering experience, mainly including fast fusepre-selection and performance verification. First, the rated parameters of fuse is selected,focusing on selecting rated current. Then fuses performance is verified, mainly includingits protection performance for thyristor and the performance of cooperating with thecircuit breaker. In the verification process, all possible failures of the converter areanalyzed, fault circuit models are built in MATLAB software for simulation, and thesimulation results are regarded as the calibration reference.The article also suggests another verification method by means of finite elementanalysis, taking advantage of that the performance and life of the fuse are related to thetemperature rise characteristics. The temperature rise of the fuse is analyzed ascomplement and compare for engineering method. Thermal electric coupling problem isanalyzed in fuse temperature rise process, and physical model of fuse is built in ANSYSsoftware to solve the problem, combining with the working conditions of PF converter.The simulation results are basically consistent with the engineering method and haveguiding significance for practical application of fast fuse thermal design. The preliminary design of fast fuse protection for PF converter is approved by theITER expert panel. The design can meet all the protection requirements, and it is enteringthe prototype testing stage now. |
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