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A fault detection method for DC lines in VSC-HVDC system based on current correlation

High-voltage direct current system based on voltage source converters (VSC-HVDC) is widely recognized as a feasible solution to cope with increasing electricity demand and integrate renewable energy sources. One of the most important issues still to be addressed is the protection of the system under DC line fault, especially for the situations using overhead lines due to higher fault frequency. This paper proposes a new fault detection method for DC line in VSC-HVDC system using the correlation of currents at DC-link capacitor branch and DC line end. In this approach, Pearson correlation coefficient is used to measure the correlation. Fault detection can be achieved easily by calculating the Pearson correlation coefficients at both ends of DC line. Simulation results using PSCAD/EMTDC demonstrate that the proposed method is able to detect the DC line fault with high selectivity and high robustness to fault resistance and noise, and it is suitable for multi-terminal VSC-HVDC system.