A multi-terminal current differential protection setting method for fully weak-infeed distribution networks based on restricted enumeration method

With the high penetration connection of inverterinterfaced distributed generators and the increasing application of large-capacity energy routers, fully weak-infeed distribution networks consisting entirely of power-electronized weak-infeed power sources are set to become one of the fundamental forms of future distribution networks. For fully weak-infeed distribution networks, multi-terminal current differential protection is considered an optional or even preferred line protection scheme. In this paper, a multi-terminal current differential protection setting method for fully weak-infeed distribution networks is proposed based on the restricted enumeration method. To address the impact of data synchronization errors and measurement errors of multi-terminal current on differential current, the problem of determining the maximum differential current superimposed with the multi-terminal current phasor errors is transformed into a high-dimensional non-convex optimization problem. The distribution law of the global optimal solution in the non-convex constraint space is deeply studied and analyzed, and a restricted enumeration method is proposed that can quickly solve the protection setting value, thereby solving the problem of multi-terminal current differential protection setting. The accuracy and rapidity of the proposed method are verified by comparing the calculation accuracy and time consumption of the restricted enumeration method and the exhaustive search. It is shown that the proposed multi-terminal differential protection setting method exhibits sufficient reliability and sensitivity in fully weak-infeed distribution networks, as verified through simulation analysis using a fully weak-infeed distribution network model built in PSCAD/EMTDC.