LAUSR

In this article, a renewable (solar and wind) energy sources based distributed generation system (DGS) is controlled to operate in the grid-connected (GC) mode and an islanded mode using the robust and fast IAPV (Improved Affine Projection Versoria) and proportional resonant based control strategy. Due to the use of IAPV-based control in the GC mode, the grid current becomes immune to the dc offset and the other nonfundamental harmonics during an unbalanced load, which significantly improves the grid current quality. It also presents the flexible operation of DGS in the GC mode using the variable and constant power injection into the grid, which ensures the grid stability during large and fast wind and solar power variations. Moreover, a modified second-order sequence frequency locked loop is used to improve the synchronization and seamless mode switching (islanded to GC and vice versa) performance by quickly and accurately estimating the phase angle and frequency at distorted and unbalanced grid voltages. Simulation and test results validate the microgrid operation and robustness of the microgrid control.