Control Coordination-Based Directional Pilot Protection for Distribution Feeders With Unmeasurable T-Connected IIDGs and Loads

There are often T-connected inverter interfaced distributed generation (IIDG) and load branches in the main feeders of active distribution network, leading to adaptability issues in existing two-terminal protection schemes. Given the flexible control characteristics of IIDGs, this paper proposes a control coordination based directional pilot protection scheme for distribution feeders with T-connected IIDGs and loads. Firstly, the variation range of measured sequence component impedance angle is theoretically analyzed to reveal the limitations of negative sequence directional pilot protection and positive sequence fault component-based directional pilot protection in feeders with T-connected IIDGs and loads. Then, a low voltage ride through control strategy of IIDG considering the action characteristics of positive sequence fault component-based directional pilot protection is proposed. In the positive sequence fault component network, the variation range of IIDG’s equivalent impedance angle can meet the constraint for the correct operation of positive sequence fault component-based directional pilot protection. Simulation results show that the proposed protection scheme can correctly identify the internal and external faults in feeders with T-connected IIDGs and loads.