A faster continuation power flow in rectangular coordinates for voltage stability assessment

Increasing variability in power systems due to significant penetration of intermittent generation has made it imperative to have faster and numerically well behaved algorithms for stability and security analysis. The continuation power flow (CPF), widely used to assess voltage stability has conventionally been used in the polar coordinates framework. In this paper, important numerical properties and behavior of rectangular coordinates version of the CPF are studied in tandem with those of the popularly used polar coordinates version. Our studies with the standard IEEE 14, 57, 118 and the 300 bus test power systems show clearly that the rectangular CPF has superior numerical properties as compared to the polar CPF. It is shown that the corrector step in the rectangular CPF takes much fewer iterations due to monotonic convergence as compared to the polar CPF where oscillatory convergence is observed. It is shown, as a consequence, that the rectangular CPF yields operating points closer to the nose point than the polar CPF for the same number of corrector iterations. This factor makes the rectangular CPF attractive as compared to the polar CPF in real time voltage stability assessment algorithms.