Advanced Grid Synchronization System for Power Converters under Unbalanced and Distorted Operating Conditions

This paper proposes a new technique for grid synchronization under unbalanced and distorted conditions, i.e., the dual second order generalised integrator - frequency-locked loop (DSOGI-FLL). This grid synchronization system results from the application of the instantaneous symmetrical components method on the stationary and orthogonal alphabeta reference frame. The second order generalized integrator concept (SOGI) is exploited to generate in-quadrature signals used on the alphabeta reference frame. The frequency-adaptive characteristic is achieved by a simple control loop, without using either phase-angles or trigonometric functions. In this paper, the development of the DSOGI-FLL is plainly exposed and hypothesis and conclusions are verified by simulation and experimental results