| This paper is emphasis on the study of circulation control mode and short fault of ITER poloidal field power supply system. PF power supply system is an important part of Tokamak equipment; it mainly consists of thyristor converters. The main converter is a 12-pulse, 4-quadrant converter rated for 45 kA, 2 kV using back-to-back thyristors.The structure and control mode of phase control converter are introduced in this thesis firstly, and then the simulation model of ITER PF power system is built in Simplorer software. The reason of current unbalance of multiple phase controlled converter has been analyzed, and a circuit model used for analyze the circuit-current is given, in which the controlled voltage source is used to descript the asymmetric degree of system parameters. Based on this circuit model, a special current-sharing controller is designed, it can be used both in current-sharing and circuit-current control modes.The short fault of converter is analyzed in this paper. A simplified model of transient thermo-impedance is used to estimate the temperature rise of the thyristor in the worst short fault.
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