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The fault location of VSC-HVDC section for grid integrated offshore wind farm is found by Empirical Mode Decomposition (EMD) using Hilbert transform (HT). The intrinsic mode function (IMF) of the fault generated in traveling wave signal retrieved at rectifier and inverter end is extracted by EMD. The HT is used to detect the magnitude and phase of each IMF. The HT of first IMF (IMF1-H) is evaluated for fault location objective and is further compared with wavelet transform (WT). The efficacy of the proposed fault location scheme is reflected in the simulation result.

SUMMARYA reliable protection system is needed for transmitting large amount of power over long distances. An alternating current-direct current mix network in offshore wind farm (OWF) interconnection with onshore grid offers a major challenge for faulty section identification. The transient faults in OWF system are simulated in MATLAB 7.10.0(R2010a). The fault signals, voltage and current, are retrieved at common collector platform and at voltage-source converter-high-voltage direct current sides of network in the OWF system. The detection capability of signal-processing techniques, Stockwell transform, empirical mode decomposition, and Hilbert transform, is explored for localization of different types of faults. In addition, fault events at onshore grid and those developed at the time of change in operating parameters are also simulated and analyzed. Further, the quantitative analysis for detection of fault events with the computation of maximum and mean indices and instantaneous time indices of the fault signal is presented in the study.Coordination of overcurrent relays is another challenging task in OWF interconnection with onshore grid system. The objective function of relay coordination problem is to minimize the operation time of associated relays. Time multiplier setting is used as the test variable in the objective function. An optimal coordination of overcurrent relays by using genetic algorithm, particle swarm optimization, and gravitational search algorithm is discussed in this paper. Further, these techniques are compared with hybrid meta-heuristic optimization method, a combination of particle swarm optimization and gravitational search algorithm to achieve relay coordination more efficiently.

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