| This paper describes a new fault current limiter (FCL) with two PWM control modules. First of all, the paper explains the importance of limiting fault current and improving power quality, and FCL is an effective means to resolve the problems. Then, the introduction of FCL's status in quo is performed.In chapter 2, through analyzing and comparing the topology and operating principles of varied types of FCLs, the paper proposed a novel FCL composed of a series reactor and a capacitor paralleled with two pulse width modulation (PWM) switched reactor modules. One IGBT and four diodes are employed to make up a PWM switch. The two-PWM-switch FCL provides continuously variable reactance by employing simple duty ratio contrl and the harmonic cancellation can be archieved for two PWM-switch modules switching instants controlled to have 1800 phase shift but equal duty. And the reactance can vary in a wide range of capacitive and inductive which can be used to limit short current or compensate reactance of line. Then, the paper proposed the methods of FCL's design and the fault detection, discussed the varying range of the reactance, analyzed the harmonic, and so on.In chapter 3, after introducing the software-MATLAB and modeling methods with it for simulation in power system, the simulation was performed with MATLAB7.0, modeling on an actual distribution network with the FCL inserted in a radial transmission line. The results in various short-circuit cases indicated that the FCL be effective in limiting the fault current and reducing the voltage sags with little harmonic generated.In chapter 4, an experiment model of the prosed FCL has been constructed and tested. The FCL was controlled with DSP– TMS320LF2407A, which control signals were magnified by EXB841 to drive and protect the IGBT– GT80J101. The results proved the validity of the FCL for limiting the fault current and reducing voltage sags. This indicates that the FCL is one of the potential devices in power system.
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