High-Frequency Fault Analysis-Based Pilot Protection Scheme for a Distribution Network With High Photovoltaic Penetration

Due to the influence of inverter control, the short-circuit current provided by distributed photovoltaics (PVs) exhibits new characteristics, such as a controlled amplitude and phase angle, resulting in the malfunction of the current protection and differential protection of distribution networks with high PV penetration. In this paper, the equivalent high-frequency impedance model (EHFIM) of PV power generation and the analysis method of a fault high-frequency superimposed network are proposed. On this basis, we analyze the fault high-frequency superimposed network of a distribution network with high PV penetration and propose a high-frequency fault analysis-based pilot protection scheme, in which the range of frequency employed for protection (FEP) is analyzed theoretically. By comparing the relationship between the high-frequency operating impedance and the high-frequency restraining impedance, the internal and external faults are identified. The proposed protection scheme has the advantages of a fast trip, low requirement for data synchronization, immunity to inverter control and the PV operation mode, and adaptability to lines with teed feeders. The experimental results show that the proposed protection scheme can accurately identify internal and external three-phase, two-phase, and two-phase grounding faults and is resistant to both fault resistance and noise interference.