Second-order sliding mode control of power converters using different disturbance observers for DC-link voltage regulation

This paper employs second-order sliding mode control (SOSMC) to carry out the current tracking and voltage regulation tasks of a grid-connected three-phase two-level power converter. For dc-link voltage regulation, a disturbance observer is adopted to improve the whole control performance. In this paper, four different types of disturbance observers are proposed for comparison, which are conventional linear observer (LINO), second-order sliding mode observer (SOSMO), linear extended state observer (LESO) and nonlinear extended state observer (NESO). To ensure fair comparison, the parameters of the observers are tuned to make the power converter achieve almost same current total harmonic distortion (THD) and steady error of dc-link voltage. The performances are compared in the term of transient response of the dc-link voltage. The simulation results show: first, the disturbance observers improve the control performance of SOSMC; second, SOSMO outperforms the other three observers.