Transient Stability Analysis and Improvement of Multiinverter-Based Microgrid

Although the transient stability of grid has been widely researched, the existing approaches focus more on the transient stability of a single type of grid connected inverter, which are not suitable for the islanded microgrid with multiple types of inverters. Therefore, this article proposes a transient stability analysis and improvement method for a multiinverter-based microgrid (MIMG). First, a large signal synchronization model of MIMG is established, which fully considers the dynamic interactions among various types of inverters, the effects of inverter locations and the time-varying of load power. Then, the concept of the feasible region of current reference of grid-following inverters (GFLs) is proposed. It can ensure that the system has stable equilibrium points (EPs). Second, the attraction domain of EPs (ADEP) is calculated by constructing a new Lyapunov’s function of MIMG. Based on ADEP, a novel stability index is proposed, which considers inverter’s dynamics and has clear upper and lower limits to accurately evaluate the system stability. Furthermore, a novel current distribution method of GFLs is proposed, which can maximize the attraction domain’s radius of EPs and then enhance system transient stability in severe faults. Finally, simulations and experiments are performed to verify the performance of the method.