A novel differential protection algorithm based on phase synchronization index for transmission line connected with photovoltaic and storage power stations

Storage power sources (SPSs) function as converter-interface power sources or loads within four quadrants, leading to fault behaviors that differ significantly from those of synchronous generators. This difference increases the maloperation risk in existing differential protection schemes that rely on the fault current flow direction. To address this issue, a differential protection scheme based on the phase synchronization index (PSI) of the current periodic differential components (PDCs) is proposed for transmission lines connected with photovoltaic and storage power stations (PSPSs). The PDCs on both ends of the protected line are introduced to reduce the impact of the fault current flow direction on identifying the internal faults. As a result, the proposed protection has good performance even if the PSPSs operate as the power sources or loads. At the same time, the PSI is used for describing the synchronization of the instantaneous phase angles of the fault current waveforms on both ends of the protected lines. It is verified that the operational characteristics of the proposed protection based on the PSI remain excellent, even under conditions of high PSPS capacities and high fault resistance. Moreover, simulations confirm that the proposed protection exhibits excellent performance in both rapid response and operational reliability. • Proposed a PSI-based differential protection scheme to bypass current direction limitations. • Introduced phase differential currents (PDCs) to mitigate PSPSs' operational impact. • Achieved reliable fault detection under high fault resistance and low fault current. • Used PSI to improve sensitivity to internal faults, including under high-resistance. • Validated performance via simulations, showing rapid response and reliability.