Synchronization techniques for grid connected wind turbines

Phase locked loop (PLL) algorithms are very important for grid synchronization in most of the grid-connected power converters applications. Particularly new grid codes for wind parks pose serious challenges to PLL. The performance of the PLL should not be affected under distorted grid conditions such as: transients, short interruptions, sags, swells, voltage unbalance, harmonics, flickers, frequency and phase variations. This paper presents a performance comparison of different phase locked loop techniques: Synchronous Reference Frame-Phase Locked Loop (SRF-PLL), Enhanced Phase-Locked-Loop (EPLL) and Quadrature-Phase Locked Loop (QPLL).