Uses and Misuses of Quasi-Static Time-Varying Phasor Models in Power Systems

Quasi-static models, also known as time-varying phasor models, have been used for many years for dynamic analysis and stability studies in power systems. However, the long track of success of using these models in a broad spectrum of applications resulted in blurring the boundaries between uses and misuses of time-varying phasors. Specifically, one possible misconception is that quasi-static models are always accurate enough when the system dynamics are slow in comparison to the nominal system frequency. This letter shows that in some cases, this assumption is inaccurate and may lead to misleading conclusions regarding the system dynamics and stability.