Improved Frequency Stability Support for Low-Inertia Power Systems

Abstract

In the renewable generation -based low-inertia power systems, frequency stability support from different types and sizes of inverter-based distributed energy resources (DERs) is of major importance. Various grid-following and -forming inverter synchronization and control methods will affect the frequency stability in different ways. In this paper, frequency stability supporting improved active power response of inverter-connected DER having synchronization based on universal frequency locked loop (U-FLL) is presented. U-FLL-based synchronization as well as active power–frequency (Pf) -droop control is further modified to achieve faster response and better frequency stability support from the studied battery energy storage system (BESS). In addition, this paper shows frequency stability comparison of U-FLL-based BESS and four grid-forming (GFM) control methods on PV-based DER unit. In the case studies with PSCAD simulation software, simplified hybrid power system model with synchronous generation and inverter-based resources (IBRs) are used to study the effect of IBRs i.e. BESS or PV on frequency stability after a load increase.