Adaptive current differential protection of line for active distribution networks considering PV output

The mass integration of distributed photovoltaic (PV) generation has altered the fault characteristics of active distribution networks, rendering the traditional overcurrent protection schemes inadequate in meeting reliability and sensitivity. Communication-based current differential protection exhibits excellent selectivity and rapid response, making it promising for active distribution network protection. However, due to the stochastic and fluctuating nature of PV output, the measured differential current and restraining current will fluctuate accordingly, degrading the conventional current differential protection’s performance. This paper proposes an adaptive current differential protection scheme that accounts for PV output. First, the amplitude and phase characteristics of PV output current under different output levels are qualitatively analyzed, considering the low-voltage ride-through (LVRT) requirements. Subsequently, the impact of PV output levels and fault resistance on current differential protection are investigated. An adaptive current differential protection scheme is proposed, which dynamically adjusts the operating threshold according to PV output and fault resistance. A simulation model of the active distribution network is built in Matlab/Simulink to validate the proposed scheme. Simulation results prove that the proposed protection scheme can adapt to PV output levels variations and maintain robustness against high-impedance faults and T-connected loads or T-connected PV.