Modeling and stability analysis for multiple parallel grid-connected inverters system

The Phase-Locked Loop (PLL) plays an important role in stability of three-phase grid-connected inverter system. However, the existing literature all neglect the influence of PLL when analyzing the stability of multiple parallel grid-connected inverters system. So this paper builds the model of the system and analyzes the system stability with considering the influence of PLL. Besides, this paper demonstrates that there exist admittance coupling among multiple parallel inverters. Thus, owing to the coupling effect, it can not obtain the multiple parallel grid-connected inverters admittance by accumulating each inverter admittance in parallel directly. Modeling the inverter mutual coupling is presented in this paper. The correctness of the modeling approach and stability analysis are verified by experimental results with RT-LAB.