Abstract-In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure of fault current limiter (FCL) is proposed. The proposed structure prevents voltage sag and phase angle jump of substation PCC after fault occurrence. This structure has a simple control method. Using semiconductor switch (IGBT or GTO) at dc current rout leads to fast operation of the proposed FCL and consequently, dc reactor value is reduced. On the other hand, the proposed structure reduces total harmonic distortion (THD) on load voltage and it has low ac losses in the normal operation. As a result, other feeders which are connected to the substation PCC will have good power quality. Analytical analysis, simulation results using PSCAD/EMTDC software and experimental results are presented to validate effectiveness of this structure. IndexTerms─Voltage sag, fault current limiter, power quality, point of common coupling (PCC), semiconductor switch, THD.

Abstract─This paper proposes a new parallel LC resonance type fault current limiter (FCL) that uses a resistor in series with the capacitor. The proposed FCL is capable to limit fault current magnitude near to pre-fault magnitude of distribution feeder current by placing the mentioned resistor in the structure of FCL. In this way, voltage of point of common coupling (PCC) does not experience considerable sag during the fault. In addition, the proposed FCL does not use superconducting inductor which has high construction cost. Analytical analysis for this structure is presented in detail and simulation results using PSCAD/EMTDC software are obtained to validate the effectiveness of this structure. Also, an experimental setup is provided to show the accuracy of analytic analyses and simulation results.

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Doubly fed induction generator (DFIG) based wind turbines are sensitive to grid faults due to utilising small-scale rotor side converter (RSC). The application of crowbar protection to improve the fault ride-through (FRT) capability of the DFIG converts it to a squirrel cage induction generator, which makes it difficult to comply with grid codes. This study proposes an innovative DC-link controllable fault current limiter (C-FCL) based FRT scheme for the RSC to improve the FRT capability of the DFIG. The proposed scheme replaces the AC crowbar protection and eliminates its disadvantages. The C-FCL does not affect the normal operation of the DFIG. By means of the proposed scheme, rotor over-currents are successfully limited during balanced and unbalanced grid faults, even at zero grid voltage. Also, the C-FCL prevents rotor acceleration and high torque oscillations. In this study, an analysis of the proposed approach is presented in detail. The performance of the proposed scheme is compared with the conventional crowbar protection scheme through simulation studies carried out in power system computeraided design/electromagnetic transients, including dc software (PSCAD/EMTDC). Moreover, the main concept of the proposed approach is validated with an experimental setup and test results are presented.