Performance improvement of a three-phase phase-locked-loop algorithm under utility voltage disturbances using non-autonomous adaptive filters

This study proposes phase-locked-loop (PLL) algorithms, which are employed to improve the performance related to the estimation of the phase angle, as well as the frequency, in three-phase systems under utility voltage disturbances. The proposed PLL schemes are based on the three-phase instantaneous active power (3pPLL), which is composed of non-autonomous adaptive filters (AFs) operating in conjunction with a positive-sequence detectors (PSDs), yielding the AF-PSD-3pPLL algorithms operating in both three-phase (abc-axis) and two-phase (-axis) stationary reference frames. The AFs are used to extract the fundamental components of the utility voltages, allowing an adequate rejection of harmonic disturbances, whereas the PSDs at fundamental utility frequency are employed for rejecting the power quality problem related to the utility unbalances. A complete stability analysis of the PLL systems is carried out. In addition, to validate the theoretical development, the dynamic response and the robustness of the proposed AF-PSD-3pPLL schemes are evaluated by means of simulation and experimental tests, taking into account utility disturbances, such as voltage harmonics and unbalances, voltage sags, phase-angle jumps and frequency variations. The effectiveness of the proposed PLL schemes are emphasised by means of a comparative analysis with the conventional 3pPLL algorithm.