PLL structures for utility connected systems

This paper presents a detailed analysis of PLL structures for utility connected systems. The three-phase PLL (phase-locked loop) structure capable of fast tracking the utility voltage vector is studied. A single-phase PLL structure, derived from the three-phase PLL topology, is discussed and its behavior under distorted utility conditions is analyzed. Additionally, the conventional zero-crossing PLL is studied and an alternative implementation for this PLL is proposed in order to improve its dynamic behavior. Simulation and experimental results from a DSP-based system are included to support the theoretical analysis.