Robust coordination of overcurrent relays for several simultaneous faults in wind power generation systems

Abstract

This work proposes a new robust coordination procedure for the coordination of overcurrent relays that takes into account the specific requirements and conditions that arise in wind power generation plants. It is discussed here that, in those systems, coordination schemes that guarantee that protection coordination is maintained in the face of the simultaneous loss of several lines in the network can be of great importance, although this characteristic is not considered relevant in the usual transmission and distribution systems. Several new features have been incorporated in the proposed procedure, for achieving the computational efficiency that is necessary for performing the proposed task. A new mathematical model is presented, considering the characteristic curves of relays as design variables and including new constraints/penalties related to the maximum desirable relay actuation time. The proposed tool integrates a Differential Evolution algorithm with Linear Programming and a new Discrete Feasibility Search operator to minimize the sum of relay actuation times in scenarios for multiple fault conditions and to maximize robustness of the solution under scenarios with changes in network topology. The proposed robust coordination procedure with those features constitutes the first coordination algorithm designed for dealing with the reconfigured topology after the simultaneous loss of multiple lines in a network. A set of Pareto-optimal solutions is delivered, allowing the designer to perform a trade-off analysis between smaller actuation times and smaller disconnected areas after the occurrence of a fault. In the specific case of wind power generation plants, those robust solutions allow a more efficient use of resources allocated to network maintenance. A case study of the application of the proposed methodology to the protection of a real wind farm is presented, showing that the proposed procedure allows a reduction of 44.9% of the non-delivered energy in the case of the simultaneous occurrence of two faults, and of 51.9% of the non-delivered energy in the case of three simultaneous faults.