A new discrete-time PI-RMRAC for grid-side currents control of grid-tied three-phase power converter

In this work, a new discrete-time direct robust adaptive PI controller is developed and applied on grid-side currents control of a three-phase full-bridge static converter connected to the electrical grid by LCL filter. The control structure is based on Robust Model Reference Adaptive Control (RMRAC) to adjust gains online, designed from a reduced-order model of LCL filter. The highlights of this controller are its intuitive design that requires a reduced set of design parameters if compared with others robust adaptive controllers for grid-tied power systems, which implies an easier implementation and less computational burden. In addition, identifier robustness and control stability are discussed in discrete-time, considering the overall plant. Experimental results are presented to corroborate the proposed control strategy and discuss its performance for grid-side currents loop control, exogenous disturbance rejection, and robustness to parametric variation of grid impedance.