Multi-Frequency Current Controller for Grid-Tied Converters

This paper presents a grid-side current controller for grid-tied inverters with LCL filter, including harmonic current elimination. Contrarily to previously proposed harmonic current controllers, the presented solution offers a generalized method that gives a consistent and stable performance irre-spectively of the number of current harmonics to be canceled and of the resonant frequency of the LCL filter. The response to reference commands is completely damped and fast. The speed is set in accordance with the low-pass characteristic of the LCL filter so as to limit the control effort. Concerning the disturbance rejection, the controller offers an infinite impedance to any disturbances (such as grid voltage harmonics) at a set of arbitrarily specified frequencies. In addition, the performance of the presented controller is evaluated in terms of a fundamental tradeoff that exists between robustness and the number of frequency components rejected. Finally, simulations and experimental results that validate the proposal are presented.