Modeling, Tuning, and Performance Comparison of Second-Order-Generalized-Integrator-Based FLLs

The second-order-generalized-integrator-based freq-uency-locked loop (SOGI-FLL) is a well-known tool for filtering and synchronization purposes in the power and energy applications. The SOGI-FLL, nevertheless, has a limited ability in rejecting the grid voltage disturbances. To deal with this problem, two advanced SOGI-FLLs have been proposed recently. In the first one, a SOGI-based filter is included inside the standard SOGI-FLL control loop, and in the second one, a SOGI-based filter is employed as the prefiltering stage of the SOGI-FLL. The small-signal modeling, tuning procedure, and detailed performance comparison of these advanced SOGI-FLLs have not been carried out yet. The aim of this paper is to cover these issues.