Robust Control Method of Grid-Connected Inverters With Enhanced Current Quality While Connected to a Weak Power Grid

Abstract

In order to improve the robust stability of the grid-connected inverter of wind power or photovoltaic power generation while connected to a weak power-grid, the robust model of grid-connected inverter under weak power-grid is established, and the influence mechanism of power-grid impedance and voltage distortion on the stability and current quality of grid-connected inverter is analyzed. On this basis, an adaptive robust <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H_∞</i> control method is proposed, in which there is no need to online measure the power-grid impedance, and the control parameters do not change with the change of the power-grid impedance. Then, the calculation method of each reference quantity and the design method of control parameters are introduced. Finally, an experimental platform is built, and the correctness and effectiveness of the theoretical analysis and the proposed control method are verified by experiments. Compared with other control methods, the adaptive robust <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H_∞</i> control method realizes the stability of the system when the power-grid impedance varies in a wide range, which optimally restrains the power-grid voltage distortion and improves the quality of grid-connected current.