UDE-based controller equipped with a multiple-time-delayed filter to improve the voltage quality of inverters

In this paper, a two-degrees-of-freedom control algorithm based on uncertainty and disturbance estimator (UDE), aimed to minimize the total harmonic distortion of inverter output voltage is proposed, possessing enhanced robustness to base frequency variations. A multiple-time-delay action is combined with a commonly utilized low-pass UDE filter to increase the range of output impedance magnitude minimization around odd multiples of base frequency for enhanced rejection of typical single-phase nonlinear loads harmonics. Marginal robustness improvement achieved by increasing the number of time delays is quantified analytically and revealed to be independent of delay order. The performance of the proposed control approach and its superiority over two recently proposed methods is validated successfully by experimental results

Uncertainty and Disturbance Estimator-Based Controller Equipped With a Time-Delayed Filter to Improve the Voltage Quality of Inverters

In this paper, a two-degrees-of-freedom control structure is proposed to minimize both total harmonic distortion and tracking error of inverter output voltage, adopting a resonant tracking controller and a modified uncertainty and disturbance estimator (UDE). Owing to the two-degree-of-freedom feature of the proposed control strategy, tracking and disturbance rejection tasks are decoupled and treated almost independently. A time-delay action is introduced into a commonly adopted low-pass UDE filter to minimize the output impedance magnitude around the odd harmonics, which is typical to nonlinear loads. Once the disturbance is properly rejected, a tracking resonant controller is designed to force the output of the nominal system to follow a sinusoidal reference with near-zero amplitude and phase error. The performance of the proposed control structure is fully verified by experimental results