Transient stability considering dynamic load in bulk power system with high DG penetration

Transient stability may be seriously affected when a large amount of distributed generators (DG) stop simultaneously during voltage sag. It is needed to analyze accurately the dynamics of bulk power system with high DG penetration. In this paper, transient stability is studied by analyzing power-angle curves of generator considering load dynamics and model order reduction in lower voltage. According to analysis, decreasing of load internal resistance after voltage sag causes transient instability of generators. The phenomenon is confirmed through simulation using one machine and one load model. This paper also presents that the simulation results might be misled by traditional bulk power system modeling such as using static load model and ignoring impedance in lower voltage. As to the numerical simulation, a large amount of DG-stopping leads to transient step out in bulk power system, and the stability is greatly improved by DG-voltage regulation.