Fractional-order reduced-order extended state observer-based controller for DC-DC buck converter with time delay estimation

Abstract Aiming to attenuate the total disturbances of a DC-DC buck converter, i.e., the mid-to-low frequency voltage ripple, load fluctuations, and input voltage variations, a novel fractional-order active disturbance rejection controller (FOADRC) is proposed in this paper. First, a novel fractional-order reduced-order extended state observer (FORESO) is developed to estimate and compensate the total disturbances through a feedforward channel. Second, the method of reducing order to achieve phase compensation is proposed to address the phase lag limitation and enhance the estimation accuracy of conventional fraction-order extended state observer (FOESO). Third, a theoretical basis for adjusting fractional order and observer bandwidth is provided by transforming FORESO into an equivalent FOTDE form in the frequency domain. Finally, the comparison of several experimental results demonstrates that the proposed FORESO exhibits better output voltage tracking performances compared to FOESO. The experimental results indicate that FORESO achieves a 16.7% improvement in RMSE, a 15% reduction in overshoot and a 10% enhancement in response speed compared to FOESO.