Small-signal analysis and modeling of parallel inverters based on the droop control method in micro-grid

This paper presents a small-signal model of parallel inverters based on the droop control method for power sharing in a stand-alone micro-grid. The control method for parallel inverters is based on the frequency-active power and amplitude-reactive power droops, which only depends on the local variable measurements. The small-signal stability is analyzed and some root locus plots are provided with the variation of some important parameters in the main circuit and the control circuit. The accuracy of the model is verified by comparing the transient process derived from the model and the transient process derived by the simulations of the original switching model. The simulation and experimental results also verify the accuracy of the prediction of system stability by root locus plots.