Abstract:  Distribution networks power supply capability (DNPSC), which reflects the current power supply margins, is a significant index to evaluate the operation state of distribution systems. The traditional maximum load multiple method is limited by heavy-loaded equipment, because all buses share the same increasing ratio and the calculation will be stopped once one constraint works while using the repeated power flow (RPF) algorithm. Therefore, the DNPSC cannot be known accurately. To solve these problems, this paper proposes a load increasing mode (LIM) and an improved repeated power flow (RPF) algorithm, which is based on sensitivity analysis (SA) of equipment power flow and buses voltage to load increasing, to calculate the DPNSC precisely. The novel LIM can adopt the SA results to reduce the influence of load increasing on the load flow of heavy equipment and bus voltage deviation; the improved RPF algorithm can provide a solution when the constraints work. The example shows that the proposed LIM and improved RPF algorithm have more accurate assessment capability, which has the referencial value for the distribution networks operation and construction.

Key words:  distribution network,  power supply capability, load increasing mode, sensitivity analysis, improved repeated power flow algorithm