A continuation power-flow for distribution systems voltage stability analysis

This paper presents a new method for tracing PV curves in radial distribution power systems. The proposed method starts at no-load and leading to the maximum loading point whereas no ill-conditioning problems were detected. In this method, the stable and unstable solutions are solved simultaneously. The stable part is calculated by first-order polynomial secant predictor and solved using the radial power-flow method. The unstable part is calculated using a two-bus equivalent model and an iterative solution process is implemented to compute the node voltages of unstable systems. Adaptive step wise control has been implemented in the two methods to improve the solution process and reduce the number of the calculated points along the traced curve. The results calculated with the proposed method for a 33-bus radial feeder show that the developed method is very efficient calculating the PV curves of radial distribution systems. The results are compared with the continuous Newton-Raphson power-flow solver for different case studies. The calculated results at different nodes of the study system are more accurate than those calculated using Newton-Raphson method. The developed method exhibits superior convergence characteristics for high R/X ratio. The results show that the proposed method fits well for distribution systems.