Symmetrical Components Detection With FFDSOGI-PLL Under Distorted Grid Conditions

Abstract

To synchronize grid-connected voltage source inverters with the grid, the knowledge about the phase angle of the fundamental, positive sequence of the supplying voltage is necessary. For additional compensation tasks, the knowledge about all symmetrical components is needed as well. A DSOGI-PLL (dual second order generalized integrator - phase locked loop) provides a method to determine the phase angle in a notable manner. Because of a co-dependency between the DSOGI and the PLL through its estimated frequency, the speed of the PI controller is limited. A solution is to set a fixed value as tuning frequency with recalculation of the resulting errors. This paper offers a method based on a frequency-fixed DSOGI-PLL to calculate the phase angle and the symmetrical components of the supplying voltage with high damping of harmonics which are inherent in it, in a fast and stable way.