I. Introduction
Proportional Integral (PI) controllers are commonly employed in power system applications [1]. The IEEE Standard 421.5-2016 is the recommended model. It proposes an anti-windup (AW) or non-windup PI control [2] model for dynamic analysis of power systems. The differential equation of this model is discontinuous. Due to discontinuity, simulations with the IEEE model can lead to failure of a numerical method or trajectory deadlock known as chattering Zeno [3]. This work applies Filippov theory (FT) to develop a method for the continuation of trajectories beyond such a deadlock point.