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 (symmetrical/asymmetrical), 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.