Small-signal terminal-characteristics modeling of three-phase droop-controlled inverters

Droop-controlled inverters are widely employed as power sources in three-phase AC power electronics system, such as distributed generation, while the interaction between the source and the load may lead overall system to be unstable. Terminal-characteristics based stability criteria are very attractive for analyzing the stability of three-phase AC power electronics system. However, the systems, composed by droop-controlled inverters, exhibit the dynamical variation of fundamental angular frequency, and existing stability analysis approaches are just suitable for systems with constant fundamental angular frequency. To overcome this problem, this paper proposes small-signal terminal-characteristics model of the three-phase droop-controlled inverter covering the dynamic of fundamental angular frequency, and both current mode operation and voltage mode operation are taken into account. Finally, the proposed model is verified in frequency domain.