Precise modeling based on dynamic phasors for droop-controlled parallel-connected inverters

This paper deals with the precise modeling of droop controlled parallel inverters. This is very attractive since that is a common structure that can be found in a stand-alone droop-controlled MicroGrid. The conventional small-signal dynamic is not able to predict instabilities of the system, so that in this paper, the combination of both small signal model and dynamic phasor model (DPM) of parallel-connected inverters is presented. Simulation results show that the dynamic phasor model is able to predict accurately the stability margins of the system when the droop control gains exceed certain values. In addition, the virtual ω-E frame power control method, which deals with the power coupling caused by the line impedance X/R characteristic, has been chosen as an application example of this modeling technique.