Modeling and Stability Analysis of DC Microgrid with Nonlinear Photovoltaic Systems Using the Describing Function Method

Due to its clean and efficient attributes, photovoltaic (PV) power generation is progressively supplanting conventional fossil fuels and assuming a more prominent role in the electric grid. However, the rising prevalence of PV systems has posed challenges in assessing system stability. This paper takes a direct current (DC) microgrid system powered by PV as an illustrative case. Instead of the traditional Maximum Power Point Tracking (MPPT) control, it adopts a power control strategy based on the perturbation and observation (P&O) method, mitigating the impact of external disturbances on PV generator power fluctuations. The describing function (DF) method is utilized to create a more precise model of the DC microgrid system and its complete control loop, incorporating nonlinear elements. This enables a thorough analysis of the influence of system parameters on system stability. Ultimately, a simulation model is established and verified.