The trend towards the decentralization of generating capacities in the power systems of many countries of the world has resulted in an increase in the proportion of distributed energy resources (DER). DER energy districts can be operated in grid-connected or island mode. Transient processes in DER energy districts are characterized by a significant increase in the rate and deviations of unified power quality indices (UPQI) from the standardized values under the influence of random interfering factors. This limits the use of traditional methods of measuring (evaluating) mode parameters, as well as signal processing parameters in digital devices, including automatic under-frequency load shedding (AUFLS). The use of Wald sequential analysis to recognize the operating modes of DER energy districts is shown to be an effective means of ensuring the soundness of decision-making in digital devices. A sequential analysis algorithm with adaptive settings for an AUFLS device was developed along with a block diagram for ensuring an increase in its response rate. Adaptive settings are generated based on the results of the preliminary simulation modeling allowing ambiguity to be reduced when recognizing the mode from one step to the next. A multichannel AUFLS device implementation having a parallel structure of processing and decision-making channels for each AUFLS stage appears to be the most effective. Recommendations are provided for the analysis of correct AUFLS functioning under the conditions of UPQI deviation in DER energy districts. © 2021, Springer Science+Business Media, LLC, part of Springer Nature.
