Chapter 19 - Virtual inertia emulating in power electronic–based power systems

Abstract

The concept of virtual inertia is adopted from the moment of inertia of synchronous generator (SG) rotating masses. The conventional power systems profit from the inertial function of numerous existing SGs to solve or improve the frequency challenges, e.g., low damping and high nadir due to the load/generation disturbances. However, the modern power systems are penetrated by a large number of the inertia-less power electronic–interfaced distributed energy resources (DERs). Hence, the rotational DER portion decreases impressively and the power system frequency experiences more intensive changes due to disturbances than the conventional SG-dominated power systems. In order to solve the low-inertia challenges of the power electronic–based power systems, the concept of virtual inertia is introduced, which is realized by applying a control function on the power electronic–interfaced DERs to mimic the SG inertial dynamics and provide the inertia, virtually. The main source of the virtual inertia is the short-term stored energy in the DC link of the DER power converters, which should be injected to the AC side according to the virtual inertia control objective. In fact, the DER power converters are controlled to surmount the low-inertia challenges including high-frequency nadir and high rate of change of frequency (RoCoF), low frequency/power oscillation damping, frequency instability, and severe changes triggering protection devices mistakenly.