Research on Dynamic and Steady-State Characteristics of Grid-Following/Grid-Forming Hybrid Control Based on Model Predictive Control

Abstract

With the rapid development of renewable energy, the widespread integration of power electronic devices into power generation systems has led to increased grid impedance and reduced short-circuit ratio (SCR), causing the grid to exhibit characteristics of weak or even extremely weak grids. This has posed significant challenges to traditional grid-following control strategies, resulting in increased grid harmonics, heightened instability risks, and frequent power generation system failures. In contrast, grid-forming control strategies, which provide active voltage support, have demonstrated superior stability in weak grid conditions. However, neither grid-following nor grid-forming control strategies alone can comprehensively meet the requirements of power systems in terms of stability, economic efficiency, and grid support. To address these challenges, this paper proposes a model predictive control (MPC) strategy that integrates grid-following and grid-forming control. First, a mathematical model of the grid-connected inverter is established, and stability analyses are conducted for both grid-following and grid-forming modes. Second, model predictive control algorithms are thoroughly investigated for both modes, and an optimized control strategy is selected through comparative analysis. Finally, the effectiveness of the proposed strategy is validated using a hardware-in-the-loop (HIL) simulation platform. Experimental results demonstrate that the proposed method significantly enhances the stability of grid-connected inverters under conditions of significantly increased grid impedance and reduced SCR, ensuring reliable operation of power systems. This approach holds substantial practical application value for modern power systems.