Improved resonant current controller for grid-tied converters

Conventional resonant controllers (RCs) are commonly used in the current control of grid-tied converters with LCL filter due to their advantages, such as zero steady-state error at both fundamental sequences, easy design process, and straightforward implementation. Nevertheless, these traditional solutions do not permit to place the closed-loop poles of the system in convenient locations when dealing with a fourth-order plant model like the LCL filter plus the computation delay. Therefore, the reference tracking and the disturbance rejection are deficient in terms of transient behavior and depend on the LCL filter. Furthermore, an additional active damping method usually has to be designed in order to ensure stability. This paper presents an enhanced current RC with stable and fast response, negligible overshoot, good disturbance rejection, and low controller effort for grid-tied converters with LCL filter. Simulation and experimental results are provided to verify the effectiveness of the proposed control scheme.