Robust Current Control of Grid-Tied Inverters for Renewable Energy Integration Under Non-Ideal Grid Conditions

This paper presents the design of a filtered tracking error based robust current controller for three-phase grid-tied inverters interfacing distributed renewable resources into the grid. An uncertainty and disturbance modeling based control law is developed for achieving the robustness against non-ideal grid conditions, including the grid impedance variations, grid voltage harmonics, and fluctuations in grid voltage magnitude (symmetricalasymmetrical), frequency, and phase. The proposed controller is shown to have superior current tracking performance to directly control the current injected into the grid being pure sinusoidal and three-phase balanced. In addition, high dynamic and tracking performance can be further ensured since all the phase-locked loops and multi-loop controllers are eliminated, which also delivers the advantage of a simple implementation. Especially, the system stability is proven by using the Lyapunov function. Both simulation and hardware-in-the-loop experimental results of the proposed robust controller, as well as the proportional-integral controller and the parallel proportional-resonant controller, are given and compared, which validates the performance and effectiveness of the proposed control strategy.