Impact of current limiters and fast voltage boosters in grid-forming VSC-based generators on transient stability

TL;DR

This work addresses transient stability in grids dominated by grid-forming VSC-based generators by evaluating hybrid current limiters (HCLs) and fast voltage boosters (FVBs). It develops a theoretical framework using the Equal Area Criterion to quantify how CSA, VI-CL, and HCL affect the $P$-$\delta$ curves and critical clearing angles, and it extends this analysis to FVBs implemented locally (FVB-L) and via wide-area control (FVB-WACS). Time-domain simulations on Kundur’s two-area system with 100% GFVSC generation demonstrate that HCLs improve stability and that FVBs further enhance transient stability, with FVB-WACS offering the strongest gains and robustness to communication latency. The results suggest that combining FVBs with HCLs provides complementary benefits, enabling larger stability margins in fault scenarios crucial for future converter-dominated grids.

Abstract

Transient stability is a complex phenomenon presented in multi-machine and multi-converter systems, and it is still considered a key limiting factor for stressed power systems. The increasing integration of non-synchronous generation further emphasises the need to address the challenges of improving the transient stability faced by these power systems. Several studies have focused on developing control strategies for GFM-VSCs to improve transient stability. These strategies include the use of current limiting algorithms and/or control of active/reactive power injections. This paper investigates the impact of fast voltage boosters (FVBs) and hybrid current limiters (HCLs) on transient stability of power systems with 100% grid-forming VSC-based generators. Short-circuit simulations and critical clearing time analysis are performed to evaluate the effectiveness of HCLs and FVBs in improving transient stability. The simulation results demonstrate the effectiveness of these approaches in avoiding the loss of synchronism. This research contributes to the current studies on transient stability in power systems and provides valuable insights into the potential of HCLs and FVBs as effective approaches to improve system stability.

Figures (20)

• Figure 1: Model of a grid-forming VSC.
• Figure 2: VSM control in a GFVSC.
• Figure 3: General scheme of the control system of a grid-forming VSC.
• Figure 4: Current saturation algorithm (CSA).
• Figure 5: Strategy FVB-L.