Small signal modeling and stability analysis on parallel photovoltaic inverters in microgrid

A small-signal model based on droop control and utilized in microgrid of photovoltaic (PV) inverters is designed in this paper. The parallel-inverter system composed of two 1kVA PV inverters with no communication line is built on the basis of small-signal model. The influence of droop coefficients on the system stability and dynamic response ability is analyzed by utilizing root locus analysis in Matlab. Through the analysis, proper droop coefficients are designed to suppress the circulating current and guarantee the system stable operation. Simulation and experimental results validate the correctness and feasibility of the small-signal model and choice of droop coefficients.