A second-order sliding mode control with active disturbance rejection for dynamic voltage restorers

This paper proposes an extended state observer (ESO)-based second-order sliding mode control (SMC) for dynamic voltage restorers (DVRs). Unlike the conventional first-order SMC and some second-order SMC (SOSMC) methods that suffer from chattering, the proposed control method can alleviate chattering and achieve finite-time convergence. Chattering suppression (i.e. eliminating discontinuities) is achieved via continuous control input which is also used to generate the pulse width modulation signals. However, while removing the discontinuities in the control input, the performance of the control method is degraded when it is subjected to disturbances. Therefore, an active disturbance rejection (ADR) based on an ESO is proposed to enhance the performance. In addition, an advanced single-phase phase-locked loop (PLL) using linear observer and quasi-type-1 PLL is also proposed. The effectiveness of the proposed method is verified through simulation and experimental results which are compared with the results of the existing SMC methods applied to DVR.