Three-stage adaptive control strategy for stability improvement of grid-connected inverter in weak grid

With the rapid development of power systems based on new energy, grid-connected inverter (GCI) is extensively utilized in new energy power system. However, the interaction between GCI and the grid impedance may easily induce system instability, especially in the case of weak grid. To improve the adaptability of GCI under different operating conditions, a three-stage adaptive control strategy based on voltage feedforward is proposed, which can switch three adaptive control strategies according to different operating conditions respectively. In each stage, SA-PSO algorithm is utilized to design feedforward path and control parameters in each operating condition sample, and then the polynomial fitting method is utilized to cover the continuous full operating range, which can be used to adaptively adjust the parameters. The proposed adaptive control strategy can ensure the better stability margin of GCI under different conditions. Finally, the OPAL-RT semi-physical experiment platform is used to verify the proposed strategy.