INVESTIGATION OF SRF-PLL SENSITIVITY TO VOLTAGE WAVEFORM DISTORTIONS DUE TO HARMONICS

This paper investigates the impact of voltage waveform distortions, caused by harmonics, on a widely utilized single-phase synchronous reference frame phase-locked loop (SRF-PLL). It defines groups of test waveforms (TWs), based on the harmonic components and magnitudes recommended by the IEC 61000-4-13 standard, with phase angles determined through a genetic algorithm (GA). This method identifies TWs featuring the most significantly shifted zero-crossings (ZCs), the highest/lowest peak values (PVs), various counts of ZCs, and step-change ZC shifts with multiple ZCs (MZCs). Additionally, an analytical method for defining worst-case ZC-shifted TWs is presented. In line with the IEEE C37.118 standard recommendations, several error indices are employed to evaluate the impact of the TWs on the SRF-PLL model. These indices include magnitude error (ME), phase angle error (PE), total vector error (TVE), frequency error (FE), and rate of change of frequency error (RFE). The results presented demonstrate complex sensitivity patterns, which should aid PLL designers in better evaluating the performance of SRF-PLLs under harmonic distortions in supply voltage waveforms, thereby improving their operation and reducing related errors. The analysis also contributes to specifying more comprehensive test methods and TWs for assessing and benchmarking the performance of PLLs and other synchrophasor measurement devices.