Simulations and experimental analyses of the active superconducting fault current limiter

This paper presents the operation principle of a new type active superconducting fault current limiter (SFCL). The SFCL is composed of an air-core superconducting transformer, a PWM converter and a superconducting magnet. The primary winding of the air-core superconducting transformer is in series with AC main circuit, and the second winding is connected with the superconducting magnet through a PWM converter. In normal (no fault) operating state, the flux in air core is compensated to zero, so the SFCL has no influence on main circuit. In the case of short circuit, by controlling the amplitude and phase angle of the second winding's current, the limiting impedance which is in series with the AC main circuit can be regulated and the fault current will be limited to a certain level. Using MATLAB SIMULINK, the simplified model of the active SFCL is created, and simulations validate this SFCL can suppress the fault current effectively. In addition, the current-limiting experiment is done with a small conventional transformer. Experimental results correspond well with simulation results. (C) 2007 Elsevier B.V. All rights reserved.