Disturbance Observer-Based Finite-Time Control for Three-Phase AC/DC Converter

For three-phase AC/DC converters, load disturbances and parameter uncertainties cause large fluctuations of the DC-link voltage, even resulting in system instability. In order to cope with this problem, the disturbance observer-based finite-time control (DOFTC) is put forward in this paper, where the finite-time disturbance observer (FTDO) is designed to fast and accurately estimate disturbances. Subsequently, the stability of the AC/DC converter closed-loop system is analyzed and theoretically proved. Finally, experimental results verify the effectiveness of the DOFTC strategy, where good dynamic and steady-state performance is achieved under load disturbance and parameter uncertainties. Compared with the enhanced state observer-based sliding mode control (ESO-SMC) and adaptive control method, the proposed DOFTC method not only reduced the fluctuations of the DC link voltage by at least 55% but also improved the transient response.