Evaluation of voltage support capability in renewable energy power systems based on voltage elasticity

The increasing penetration of power electronic devices has intensified converter–network interactions, leading to more complex voltage dynamics and limiting the applicability of conventional voltage support assessment methods. To address this issue, this paper proposes a voltage elasticity index. By incorporating the pole-zero distribution of the closed-loop system, a quantitative mapping relationship between frequency-domain characteristics and time-domain responses is established, which can effectively characterize key dynamic features following perturbation, including voltage sag depth and recovery rate. Based on this index, single-converter grid-connected systems with grid-following (GFL) and grid-forming (GFM) converters are first investigated to reveal the effects of control structures and key parameters on voltage elasticity and voltage dynamic behavior. Furthermore, for power-electronics-dominated power system, the impact of GFL and GFM converter capacities at weak points of voltage elasticity is analyzed. Finally, simulations and hardware-in-the-loop experiments are conducted to validate the effectiveness of the proposed index. The results demonstrate that the proposed index provides an effective frequency-domain perspective for assessing the dynamic voltage support capability of power-electronics-dominated power systems.