Predefined-Time Observer-Based Sliding Mode Control for Fast Frequency Support in Heterogeneous Power System Through Grid-Forming Converter

A low inertia heterogeneous power system with a substantial share of renewable energy and extensive use of power electronics suffers from serious frequency stability problems when it is subjected to disturbances. The grid-forming (GFM) converter based on virtual synchronous generator (VSG) control exhibits voltage source characteristics and provides inertia and frequency support. This paper proposes a predefined-time observer-based sliding mode controller (PTOBSMC) for the VSG-based GFM converter to provide frequency support in the heterogeneous power system with large load and grid-following (GFL) renewable energy variation. The model of the heterogeneous power system, which consists of GFM converter, GFL renewable energy, and synchronous generator, is established. The predefined-time observer is proposed to accurately estimate the fluctuations in both the output power of GFL wind turbines and the load power. The observer is specifically engineered to ensure that the estimation error progressively diminishes and ultimately reaches zero within a predefined time. Based on the predefined-time observer and sliding mode control, the PTOBSMC is proposed to regulate the GFM converter to provide frequency support and facilitate the rapid restoration of the frequency of the heterogeneous power system within a predefined time. The Lyapunov function is employed to analyze the predefined-time stability of the heterogeneous power system under the proposed PTOBSMC. Comparative results obtained through Matlab/Simulink demonstrate that the proposed PTOBSMC exhibits remarkable robustness and superior performance for the heterogeneous power system.