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

With the large-scale integration of photovoltaic (PV) renewable energy into power grids, a reduction in grid inertia and diminished robustness have been observed, resulting in significant voltage fluctuations when the system is subjected to disturbances. The widely applied Proportional-integral (PI) control has been found to lack rapid response capability to external disturbances and is unable to estimate uncertainties in the model, making it unsuitable for voltage control in PV grid integration. To address these issues, a voltage active support method based on an extended state observer (ESO) and terminal sliding mode control (TSMC) is proposed. First, a grid-connected PV microgrid model was established in the Matlab/Simulink environment. Then, the voltage controller within the virtual synchronous generator control was redesigned by incorporating ESO and TSMC, based on synchronous generator control and nonlinear robust control techniques. Active voltage support and improved control performance were achieved through this integration. Simulation results indicate that, compared to PI control, the voltage controller based on ESO and TSMC effectively reduces system voltage overshoot and enhances the speed of voltage response during PV output fluctuations, due to the improved ability to accurately estimate internal parameter uncertainties and external disturbances, thereby significantly enhancing system stability.