Modified Uncertainty and Disturbance Estimator for Enhanced Periodic Signals Suppression

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

“…Since in practical cases expected frequency deviations are quite small, substantial robustness improvement may be expected. Application of a non-ideal low-pass filter Q(s) with cutoff frequency F influences HfM(s) as follows: for << F, (29) -(32) remain valid while for F performance degradation takes place, as pointed out in [23]. Bode diagram of |HfM(j )| combined with a F = 20 0 first-order Butterworth filter versus normalized frequency is depicted in Fig.…”

“…There, UDE controller equipped with a multi-band-stop-filter (MBS) was utilized to tackle the challenge of inverter output voltage quality enhancement. In [23], UDE controller equipped with a time-delayed-filter (TD) was proposed to improve its ability to approximate and eliminate signals characterized by periodic behavior and applied in [24] to single-phase inverter output voltage quality enhancement. Performance comparison between systems based on the two filters above under similar operating conditions indicated the superiority of TD in terms of both output voltage THD and settling time and the supremacy of MBS in terms of robustness to fundamental frequency variations.…”

“…Therefore, this paper mainly aims to improve the performance of UDE based controller equipped with a time-delayed-filter in terms of robustness to fundamental frequency variations by increasing the number of delays in the time-delayed-filter, i.e. utilizing a multipletime-delayed filter (MTD) rather than single-time-delayed filter, employed in [23] and [24].…”

“…It must be emphasized that utilizing a TD-based UDE yielded results somewhat similar to repetitive-like action [25]. Yet, as indicated in [23], the proposed method possesses significant fundamental difference owing to the two-degreesof-freedom structure. Nevertheless, due to revealed similarities, design rules and underlying constraints of oddharmonic repetitive control [26] - [28] are very helpful in designing TD-based UDE.…”

“…In case the LUD estimator is properly designed, then ucd(t) ≈ ud(t) and ( Apparently, if Gf(s) possesses unity gain and zero phase at odd multiples of 0, then corresponding Hf(s) = 0 and LUD in (6) will is fully attenuated. Since the LUD in (6) contain odd harmonics only, then 0 ( ) 15with ∆T denoting the delay of Q(s) at 0 [23]. The resulting Gf1(s) is referred to as time-delayed filter in [24].…”