Observer-Based Sliding-Mode Control for Grid-Connected Power Converters Under Unbalanced Grid Conditions

• Published in: IEEE transactions on industrial electronics (1982) 2022-01, Vol.69 (1), p.517-527
• Main Authors: Yin, Yunfei, Vazquez, Sergio, Marquez, Abraham, Liu, Jianxing, Leon, Jose I., Wu, Ligang, Franquelo, Leopoldo G.
• Format: Article
• Language: English
• Subjects: Adaptive control; Algorithms; Controllers; Electric potential; Frequency control; Observers; Phase current; Phase locked loops; Power converter; Power converters; Reactive power; Resonant frequency; Robust control; Sliding mode control; super-twisting algorithm; super-twisting differentiator; super-twisting observer; Tracking loops; Twisting; Unbalance; unbalanced grid; Voltage; Voltage control
• ISSN: 0278-0046; 1557-9948
• DOI: 10.1109/TIE.2021.3050387

This article proposes a novel robust control strategy for three-phase power converters operated under unbalanced grid conditions. A consolidated control objective is obtained in the stationary \alpha \beta frame, which can be flexibly adjusted according to the degree of oscillation in the active and reactive powers and the balance of the three-phase current. Based on the dynamics of the converter and control objective, a control scheme in a cascaded framework is presented, in which an adaptive observer is applied to estimate the positive and negative sequences of the grid voltage. In the current tracking loop, a super-twisting algorithm current controller coupled with a super-twisting differentiator is implemented to track the current references, featuring rapid dynamics, and improved robustness. Additionally, in the voltage regulation loop, an effective composite controller is developed to regulate the dc-link voltage, where a super-twisting observer is used to estimate the load disturbance, thereby improving the performance of the converter. The experimental results are provided to confirm the effectiveness and superiority of the proposed control strategy.