A Direct Adaptive Controller With Harmonic Compensation for Grid-Connected Converters

Abstract

Grid-connected converters are uncertain time-varying systems, whose controllers must deal with the relevant inductive content and high harmonic distortion of the sampled voltages. Adaptive controllers are feasible control strategies for these applications, because their gains are continuously adjusted in response to system perturbations, and they are also robust to unmodeled dynamics and exogenous disturbances. However, adaptive controllers are not necessarily capable of rejecting all harmonic components on grids with high harmonic distortion. Therefore, this work presents a Robust Model Reference Adaptive Control-based with an adaptive super-twisting sliding mode, which is improved with a harmonic compensation strategy in which additional control actions to deal with the harmonic contents of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$5^{th}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$7^{th}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$11^{th}$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$13^{th}$</tex-math></inline-formula> of the fundamental component of the electrical grid are incorporated into the control structure. Experimental results are provided of a 7.5 kW converter connected to a distorted and unbalanced grid with an LCL filter, where the developed control structure presents a total harmonic distortion (THD) of 2%, while the controller without harmonic compensation obtains a 2.5% THD.