Transient Stability Analysis and Enhancement of Inverter-Based Microgrid Considering Current Limitation

Affected by the current limitation, grid forming inverters (GFMs) will transition to a current source under grid faults, which makes the inverter-based microgrid lose the voltage support and then be switched to a current source interconnection microgrid (CSIM). It may deteriorate the system transient synchronization stability (TSS). This issue has not been studied previously. To this end, this paper proposes an analysis and enhancement method of TSS of CSIM. Firstly, a large signal synchronization model of CSIM is derived, which takes into account the effect of the current limitation strategy of GFMs and the dynamic interactions between GFMs and grid-following inverters (GFLs). Secondly, by constructing the Lyapunov energy function, the criterion of TSS is obtained and the impacts of parameters on stability are investigated. Based on the stability criterion, the feasible region of current references of GFLs is clearly described. Therefore, a dynamic current control method of GFLs is proposed. It can well address the absence of equilibrium points (EPs) and strengthen the transient stability. Meanwhile, a novel anti-windup strategy of GFMs considering synchronization stability constraint is proposed, which can contribute to the fault recovery of GFMs. Finally, simulation and experimental results verify the effectiveness of the proposed methods.