Abstract
This work studies the application of short-time Fourier transform (STFT) to extract current harmonics of various fault types to design a protection method for meshed multi-terminal voltage source converter-high-voltage direct current (VSC-HVDC-MTDC) grids. The frequency spectrum of fault current harmonics is used to detect internal and external faults, the faulty pole and fault type. The method does not need the implementation of series inductance on the sides of the DC lines and it is also effective for lines combining overhead lines and cables. The window function and hop size play the primary role in STFT, which are investigated in a sensitivity analysis. A modified version of CIGRE meshed DC grid system is simulated in PSCAD in order to show the robustness of the method, and further signal processing analysis is done in MATLAB. The results show the accurate detection and discrimination between faulty sections using the proposed harmonic-based method and how important the STFT parameters are in order to have a robust protection algorithm.
Highlights
Voltage source converter-based high-voltage DC transmission (VSC-HVDC) has a key role in future power transmission
This paper investigates the application of short-time Fourier transform (STFT) for fault analysis of VSC–MTDC systems, concentrating on DC section and different DC fault types
Application of STFT for harmonic-based protection of meshed VSC-MTDC grids is studied in this paper
Summary
Voltage source converter-based high-voltage DC transmission (VSC-HVDC) has a key role in future power transmission. The algorithm is only proposed for point-to-point HVDC and is not tested for VSC-MTDC grids. It did not use the distributed frequency-based models of cables in the model. Wavelet transform (WT), DFT and STFT are the main signal processing methods used to design power system protection algorithms. Both WT and STFT have advantages and drawbacks in fault signal processing, in frequency domain analysis. This paper investigates the application of STFT for fault analysis of VSC–MTDC systems, concentrating on DC section and different DC fault types.
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