DC-link voltage stability analysis for single-stage photovoltaic VSIs connected to weak grid

Solar energy can be effectively utilized as the grid-connected photovoltaic (PV) generation system. But in weak grid, the non-ignorable network equivalent impedance is a great challenge for the stability of grid-connected voltage source inverters (VSIs). This paper focuses on the single-stage three-phase grid-connected PV inverter, presents a small signal model of PV inverter, and gives a physical insight by making an analogy between synchronous machine rotor movement and DC-link voltage dynamics of PV VSI to analyze the stability of DC-link voltage in VSI when connect to weak grid. The impact of P-V characteristic of PV array on single-stage PV inverter is discussed. Simulation results of PV power system, which includes grid-connected PV VSI and PV array, are given to verify the analysis.