Analysis of Grid-forming/following STATCOMs and Synchronous Compensators for Grid-following IBRs stability

Abstract

This paper investigates how different compensating devices can enhance the small-signal stability of the system by means of the phase-locked loop (PLL) in inverter-based resources (IBRs) operating in grid-following mode. Three technologies are compared: synchronous compensator (SC), STATCOM operated in grid-forming (GFr) mode, and static synchronous compensator (STATCOM) operated in grid-following (GFl) mode. A systematic control design procedure is proposed for the GFr STATCOM, combining pole-placement for the inner current loop and phase margin design for the outer voltage loop. The study relies on small-signal eigenvalue analysis and time-domain simulations under transient disturbances. To provide a representative case study, a doubly-fed induction generator (DFIG) is used as the IBR device model due to its complex dynamics and direct coupling between the machine and the grid. Results confirm that both SC and GFr STATCOM significantly improve the system stability, whereas GFl STATCOM provides negligible benefits.

This paper investigates how different compensating devices can enhance the small-signal stability of the system by means of the phase-locked loop (PLL) in inverter-based resources (IBRs) operating in grid-following mode. Three technologies are compared: synchronous compensator (SC), STATCOM operated in grid-forming (GFr) mode, and static synchronous compensator (STATCOM) operated in grid-following (GFl) mode. A systematic control design procedure is proposed for the GFr STATCOM, combining pole-placement for the inner current loop and phase margin design for the outer voltage loop. The study relies on small-signal eigenvalue analysis and time-domain simulations under transient disturbances. To provide a representative case study, a doubly-fed induction generator (DFIG) is used as the IBR device model due to its complex dynamics and direct coupling between the machine and the grid. Results confirm that both SC and GFr STATCOM significantly improve the system stability, whereas GFl STATCOM provides negligible benefits.