DSOGI based Grid Synchronization under Adverse Grid Conditions

This paper discusses the design together with the application of a Double Second Order Genralized Integrator (DSOGI) for grid integration. A moderately distorted supply (having a THD equal to 8.49%) feeds a non - linear load and a Shunt Active Power Filter (SAPF) is used for as a compensator. In this paper, two different control approaches have been used to derive reference currents for the SAPF. These algorithms are the unit template (UT) based controller and synchronous reference frame (SRF) theory based approach. Both the algorithms fail to achieve less than 5% distortion in supply currents when used under distorted/ polluting grid conditions. Hence a DSOGI based controller has been realized to generate perfectly sinusoidal reference currents even under adverse grid conditions. With the proposed modification in the controller design using the DSOGI block, perfectly sinusoidal grid currents can be generated. System has been simulated in MATLAB environment using SIMULINK and PSB toolboxes. Performance results demonstrate the effectiveness of DSOGI based non - phase locked loop approach for grid synchronization.