Inertia and Damping Analysis of Grid-Tied Photovoltaic Power Generation System With DC Voltage Droop Control

Photovoltaic power generation relies on power electronics and therefore does not have natural inertia and damping characteristics. In order to make the capacitance of the medium time scale participate in the grid frequency response without adding additional equipment, this paper takes the grid-connected photovoltaic power generation system based on DC voltage droop control as the research object, and establishes the static synchronous generator (SSG) model of the system. The model is used to analyze the main parameters affecting the inertia, damping and synchronization characteristics of the system and their influence laws. 

The research results show that the energy storage effect of the capacitor on the medium time scale can also make the system exhibit certain inertia characteristics. From the point of view of control parameters, as the droop coefficient Dp decreases, the inertia characteristic exhibited by the system is stronger. The larger the DC voltage outer loop proportional coefficient Kp is, the stronger the damping effect of the system is. The larger the DC voltage outer loop integral coefficient Ki, the stronger the synchronization capability of the system.

Keywords: Grid-connected photovoltaic power generation system, DC voltage droop control, inertia characteristic, damping effect, synchronization ability.