A Study on the Relation between the Maximum Loadability Point and Undervoltage Load Shedding Schemes

In Electrical Power Systems (EPS), traditional voltage stability assessment techniques are based on the solution of algebraic equations to identify the static voltage stability margin (VSM) and the maximum loadability point (MLP) of the system. The estimation of the VSM and the MLP depends on the load growth direction and also on possible events that may occur as the load increases. The main contribution of this paper is to highlight that the actions of undervoltage load shedding (ULS) schemes are important for correct VSM and MLP estimation, which is made through a detailed explanation of the dependence of the MLP on the ULS schemes under contingencies. The paper also shows scenarios where the MLP is reached before any ULS scheme is triggered. The shape of the PV curves in these scenarios where no ULS scheme is activated is shown for a reduced order model of the South-Southeastern part of the Brazilian Interconnected Power System.