Analysis on Interaction between Three Phase PV Grid-Connected Inverter and Week Grid

Power grid is a weak grid with internal impedance for grid-connected PV generation system. The grid impedance has serious impact on system stability and power quality for PV grid-connected system. To study the interaction between grid-connected inverter and weak grid, the Norton equivalent output impedance model and state space representation of the PV grid-connected system is established in this paper. Then stability of PV grid-connected system is analyzed by root locus, Jacobian matrix and Nyquist criterion and stability domain of single parameter, dual parameter and multi parameter for different grid impedances are given. Validity of the stability analysis for grid-connected interactive system is verified based on MATLAB simulation. Research results show that grid impedance will worsen the power quality, degree the phase margin and control performance and reduce the stability margin for the grid-connected system. Appropriately increasing the DC capacitor or change the controller parameters can improve the system stability.