Robust current control of grid-connected converters with LCL-filter

This paper presents a robust current controller for grid-connected converters with LCL-filter. The design of the controller considers uncertainty on the grid impedance parameter and includes an internal model structure that ensures asymptotic tracking of the sinusoidal current reference as well as disturbance rejection of the background voltage. A state feedback control law, which depends on the states of the converter and of the internal model controller, is considered here. Then, a robust design is developed on linear matrix inequalities framework. Results that verify the robust stability and good performance of the proposed current controller are presented for different cases of grid impedance at the point of common coupling.