Adaptability Analysis and Performance Enhancement Strategy of the Sequential Component Based Scheme for the Photovoltaic Plant Exporting Line

[Objective] This analysis focused on the adaptability of the traditional sequential component phase selection element after connecting the photovoltaic power supply to the system. The positive- and negative-sequence impedances of the photovoltaic side differ significantly， resulting in unequal positive- and negative-sequence distribution coefficients. This leads to a significant increase in the failure risk of the photovoltaic phase-selection element in the grid-connected system. Therefore， this paper proposes a performance enhancement strategy for sequential component phase selection elements in photovoltaic （PV） plants， considering load participation and energy storage regulation. [Methods]The proposed scheme adjusts the positive- and negative-sequence distribution coefficients of the key conditions in the phase selection principle to the same value on the photovoltaic side using the energy storage system and plant load. Thus， the phase selection capability of the sequential component phase selection element is restored. [Results]The simulation results from PSCAD/EMTDC demonstrate that the proposed control strategy can effectively restore the phase-selection capability of the phase-selection elements under various complex fault conditions with high sensitivity. [Conclusions] The phase-selection element can effectively perform its phase-selection function under various fault conditions， including those involving transition resistance， thus ensuring accurate phase selection. It can complete the selection process within the time constraints required for the subsequent protection operations， thereby demonstrating high reliability.