Nonlinear Stability Analysis of the Conventional SRF-PLL and Enhanced SRF-EPLL

Phase-locked loop (PLL) systems play a crucial role in grid synchronization. Since variations on the voltage parameters are general uncertain, dynamics of PLLs by nature nonlinear. This fact imposes relevant challenge to guarantee their stability. Unfortunately, as argued this paper, there is remarkable lack global stability tests even for most common approaches, such synchronous reference frame (SRF). In case, only available small-signal—linearized—model-based approach The main issue resorting local conclusions that synchronization forced operate under conservative conditions, where large-signal forbidden. Needless say, has detrimental impact applications, since performance limited small disturbance assumptions. Motivated problem, present work, we provide asymptotic two fundamental PLL algorithms. Namely, conventional SRF-PLL and enhanced SRF-EPLL. To do so, use Lyapunov acting directly nonlinear trajectories. Consequently, provided proofs not rely any linearization technique, frequency-domain conversion, or small-signal model representation. contribution paper set conditions valid sense. Moreover, it shown these results have direct practical implications form new robust gain tuning guidelines.