Low Voltage Distribution Network TN-S Impedance Identification Considering Single and Three-Phase Hybrid Connection

The low-voltage distribution network (LVDN) terrestrial-neutral-separated (TN-S) impedance refers to the nodal resistance and reactance values on a three-phase five-wire line. The distributed photovoltaics and electric vehicles are increasingly integrated into the LVDN in either single-phase or three-phase mode. It will aggravate the three-phase unbalance, produce unbalance current in the neutral line, which brings difficulties to phase decoupling for impedance estimation. In this regard, this article proposes a LVDN TN-S impedance identification method that considers the single-phase and three-phase hybrid connection. Specifically, a LVDN line impedance model containing the neutral and phase line coupling relationship is proposed. Subsequently, the self-impedance of the phase and neutral line is modeled using a hierarchical-multiple regression, and the mutual impedance estimation model is proposed to investigate its impact on the TN-S line impedance. Then, a joint cross-iterative algorithm is devised to improve the accuracy of impedance identification. Finally, the effectiveness and accuracy of the proposed method are verified through a simulated 30-node LVDN test and an actual community system.