Sliding Mode Control for Power Converters Under Unbalanced Grid Conditions

This chapter 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 AO is applied to estimate the positive and negative sequences of the grid voltage. In the current tracking loop, a STA current controller coupled with a STD 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 STO 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.