A fast method for load margin estimation considering the reactive power generation limits

In the context of voltage stability, this paper describes a fast algorithm that estimates the maximum loadability point (MLP) of a power system from its power flow equations. First it estimates the load level where each generator reaches its reactive limit, this is done using a quadratic curve fitting technique. After that another quadratic curve is used to estimate the MLP. From two power flow solutions, the algorithm is able to find the MLP without taking any continuation power flow (CPFLOW) steps. The proposed method was applied to the IEEE 57 and 118 bus test systems. When compared to the CPFLOW the estimated MLP error was less than 3%. The algorithm is fast and accurate which makes it adequate for real time voltage stability assessment and contingency analysis.