Research on Nonlinear Robust Control Strategy of Active Voltage Support for Grid-forming Photovoltaics

Abstract With the integration of a large number of photovoltaic renewable energy into the power grid, on the one hand, it will lead to a decrease in the proportion of synchronous generators with large inertia in the power grid, and on the other hand, because photovoltaic needs to be connected to the grid through inverters and other devices containing a large number of power electronic components, the inertia of the power grid will be reduced, the robustness will become poor, and the system voltage will fluctuate. In order to solve the above problems, this paper proposes a voltage active support method based on the expansion state observer and the terminal sliding mode control strategy. Firstly, a grid-forming photovoltaic grid-connected microgrid model was built in Matelab/Smulink. Secondly, the voltage controller in the virtual synchronous generator control was redesigned according to the synchronous generator control and nonlinear robust control technology. By adding an extended state observer and terminal sliding mode control to the voltage controller, the purpose of active voltage support and improved control performance is realized. Through simulation analysis, the results show that when the photovoltaic output changes, the voltage controller based on the expansion state observer and terminal sliding mode control can not only realize the voltage regulation function, but also effectively reduce the overshoot of the system voltage, improve the voltage response speed, and enhance the system stability of the system when the photovoltaic output changes.