Work

Transient Synchronization Stability Analysis and Control of GFLC and GFMC Hybrid Systems under Current Limiting Constraints

Year: 2026

Type: article

Abstract: To maximize active power output and provide grid support, many renewable energy stations are evolving into hybrid systems integrating both grid-following converters (GFLCs) and grid-forming converters (GFMCs). However, due to the limited overcurrent capability, both GFLCs and GFMCs are equipped with current limiters for device protection. It may cause the change of operating modes and control strategies under faults, thus inducing complex transient interactions and synchronization instability issues. To address these problems, this paper describes the stability boundaries of the hybrid system and proposes a current limiting coordinated (CLC) strategy to enhance the transient synchronization stability (TSS). By establishing the model under current saturation and analyzing the effect of interaction terms, it is revealed that interaction in hybrid systems may cause converters to lose equilibrium points under faults and usually has a more significant impact on the GFLC than on the GFMC. Then, with the Lyapunov energy function, the TSS region described by the saturated current phases is derived. It is found that reasonably adjusting the saturated current phases can enhance the TSS. Therefore, a novel current limiting strategy based on saturated current phases coordination is proposed to ensure the TSS of the hybrid system. Finally, the analysis results and proposed strategies are verified by simulations of a GFLC and a GFMC connected to an IEEE 39-bus power grid and hardware-in-the-loop experiments.

Source: IEEE Transactions on Sustainable Energy

DOI: 10.1109/tste.2026.3735449