Optimal Settings for Adaptive Overcurrent Relay Coordination in Grid-Connected Wind Farms

Abstract

– In wind-integrated substations, the setting of the over current relays (OCRs) must be appropriately selected on line with the variations in fault levels, which in turn change with the wind-speed dynamics. An adaptive technique for the coordination of the OCRs is suggested as a solution for avoiding the mal-function of the relays. This paper proposes an algorithm in which wind speed is forecasted and the optimal settings of the relay are calculated in the preceding interval. The artificial intelligence methods selected are hybrid adaptive neuro-fuzzy inference system (ANFIS) and seasonal auto regressive integrated moving average (SARIMA) method for the prediction of the wind speed, and hybrid pattern search (PAS) and linear programming (LP) approach for selecting the optimal relay settings. The proposed algorithm is validated for the modified IEEE 30-bus system with wind farms and also for a typical wind-integrated system in simulated studies. The simulation has been carried out using electrical transient analysis program (ETAP) and MATLAB software packages. The results show that the proposed method reduces the computational time for determining the optimal OCRs and minimizes the operating time of main and back up relays compared to the conventional algorithms while maintaining the coordination time interval (CTI).