Sensitivity analysis of voltage limit in radial AC microgrids considering the loading condition and line length

Abstract

A sensitivity analysis of voltage compliance in radial AC microgrids linked to a low-voltage main grid is presented in this paper, with an emphasis on the combined effects of feeder length and load-generation balance. Three loading scenarios: demand exceeding generation, demand matching generation, and generation exceeding demand are used to apply a Newton-Raphson power flow algorithm to a radial network with five distributed generators (DGs) and five loads. Feeder lengths, both long and short, are assessed for every condition. The findings indicate that voltage falls below the IEEE 1547 lower limit of 207 V when demand exceeds generation with long feeders (200 m line sections), falling as low as 166.9 V at the farthest load, potentially causing load shedding and DG disconnection. On the other hand, even in extended feeder situations, voltages stay within the acceptable ±10% range when generation matches or surpasses demand. These results offer useful recommendations for feeder design and DG placement in grid-connected microgrids, as well as quantitative insights into worst-case operation scenarios.