A novel protection scheme for VSC‐HVDC transmission lines based on current integral autocorrelation.

Voltage source converter‐based high voltage direct current (VSC‐HVDC) transmission system has become the mainstream of power construction and plays an increasingly important role in the power system. However, the DC line fault results in shutting down of the converters, which can greatly endanger the security of the power grid. So it is essential to find a fast fault identification strategy for DC line protection technology. In addition, the existing backup protection scheme has the problems of long delay and strict communication synchronisation requirements. Therefore, this study proposes a novel protection scheme for VSC‐HVDC transmission lines based on the fault current integral autocorrelation coefficient. The fault current and fault current frequency characteristics of VSC‐HVDC transmission lines are analysed first. Second, this study proposes a method to filter out distributed capacitance current by current integration and eliminate the oscillation of fault current. Finally, the difference of the current integral during different faults (internal or external fault) is analysed, and the autocorrelation coefficient is introduced to express the difference. Hence, this study proposes a new principle for identifying faults using the autocorrelation coefficient of the fault current integral. Simulation results show that the protection principle is not affected by the distributed capacitive current and does not require strict communication synchronisation. It has an excellent performance in intolerance to fault resistance and noise interference and can be used as backup protection for VSC‐HVDC transmission system. [ABSTRACT FROM AUTHOR]