A Robust Model Predictive Control for PLL-Based Grid-Connected Converter Under Weak Grids

The grid-connected converters (GCCs), synchronized by the phase-locked loop (PLL), often encounter harmonic stability challenges, particularly in weak grids. While several stabilizing control strategies have been proposed in the past, they often suffer from various limitations, including complex loop redesign and trade-off between performances. In this paper, a model predictive control (MPC)-based stabilizing approach is introduced to address the stability concerns. The MPC offers easy to implementation, fast transient response, and strong robustness. Furthermore, a disturbance feedforward (DF) concept is incorporated into the MPC framework. This integration effectively decouples the interaction between the PLL and the grid impedance, enhancing the stability margin of the system. To demonstrate the effectiveness of the proposed solution, theoretical analysis and simulation results are provided in the paper.