Modelling and Analysis of a Dual-Loop Current Control Strategy for Grid-Tied Inverters with LCL Filter

In the recent development of microgrids, grid-tied inverters and their control techniques have played a vital role in the power injections from the renewables into the grid. Different control techniques exist in the literature on the ability to suppress the resonance peak of an LCL filter using active and passive damping techniques for grid-tied inverter applications. However, the most crucial challenging factor for the various control techniques is the presence of computational delays and dead time involved in real-world systems, which can potentially impact the stability and performance of controllers. This paper presents the formulation of a dual-loop current control strategy in a synchronous reference frame for grid-tied inverters equipped with an LCL filter. It brings out the significance of feedforward and decoupling terms in obtaining proper plant models and the capacitor voltage buildup for smooth synchronization. Finally, the impact of inverter delay and dead time on controller design is validated through MATLAB/Simulink and HIL results.