Novel flexible algorithm for the operation of renewable source grid interface VSCs under unbalanced voltage sags

This study deals with a newly-conceived control strategy for three-phase grid connected VSIs used for distributed generation (DG) system with renewable energy sources. This strategy has been called SCCA (Symmetrical Component Control Algorithm). The SCCA aims that DG power plants can avoid overcurrent while helping to mitigate the adverse effects of unbalanced voltage sags for continuous operation. For this, it accomplished simultaneously the control of the injected currents and active and reactive power flow. A simulation comparison among five published methods and SCCA is presented in terms of quality of the injected current and ripple of the injected powers. The extensive MATLAB/Simulink simulation studies of SCCA concept demonstrate that the proposed strategy outperforms the majority of already published strategies in terms of the above criteria.