Transient Stability Analysis and Enhancement of Grid-Forming and Grid-Following Converters

The increasing prevalence of grid-following (GFL) converters in modern power systems raises concerns about transient stability, mainly stemming from loss of synchronization (LOS). In certain scenarios, grid-forming (GFM) converters are utilized to improve system stability. Existing literature focuses on the transient stability analysis of individual converter types, with limited attention given to hybrid systems incorporating both GFL and GFM converters. Particularly, the interactions between these converter types, concerning transient stability, are seldom discussed, and stability enhancement in such systems remains unexplored. To address this gap, this article aims to investigate the interaction mechanism of paralleled GFL and GFM converters and propose a control strategy to mitigate the risk of LOS in hybrid systems. The article presents detailed aggregated models, theoretical analysis, and the control design of the proposed scheme. Theoretical analyses and the proposed method are validated through simulation and experimental results.