Differential Protection Sensitivity Enhancement Scheme for AC Transmission Lines Connecting to VSC-HVDC Station

With the vigorous development of renewable energy and the popularization of HVDC transmission, the structure of power sources has changed a lot. The output current amplitude of power electronic devices is limited, the phase angle of current is controlled, and the characteristics of the sequential component are affected by the converter control strategy, which are different from fault characteristics of SGs. When the AC power system is connected to a large-capacity cross-area VSC-HVDC station, the sensitivity of the conventional current differential protection is reduced during fault on AC transmission line connecting to VSC-HVDC station. To solve the problem of insufficient sensitivity of conventional differential protection on AC transmission line connecting to VSC-HVDC station, this paper analyzed the fault characteristics of AC transmission line connecting to VSC-HVDC station during fault and proposed a current differential protection sensitivity enhancement scheme applicable to AC transmission line connecting to VSC-HVDC station. The scheme can improve the protection performance of the AC transmission line connecting to VSC-HVDC station, supporting the construction of a new type power system.