A VERSATILE HARMONIC CONTROL APPROACH FOR THREE PHASE INVERTER IN GRID CONNECTED PV SYSTEM WITHOUT CRITICAL ISLANDING DETECTION

A versatile harmonic control approach for three phase inverter in DG for PV cell with MPPT based on P&O Technique that enables both islanded and grid-tied modes of operations with no need for switching between two corresponding controllers/critical islanding detection is implemented using MATLAB/Simulink. The demonstrated versatile harmonic control approach composes of an inner inductor current loop and a simple voltage loop in the SRF. The inverter is regulated as a current source just by the inner inductor current loop in grid-tied operation and the voltage controller is automatically activated to regulate the load voltage upon the occurrence of islanding. An inductor current control loop is essential for obtaining high power quality in grid connection of inverters. It provides three-phase balanced current injection to the grid. Another advantage of using current control is that non linearities, such as inverter switching and external disturbances such as changes in the dc-link voltage Vdc and disturbance of the grid voltage Vg , are dealt within that loop. Thus, the control approach does not need a forced switching between two distinct sets of controllers. Moreover, the waveforms of the grid current in the grid-tied mode and the load voltage in the islanding mode are distorted due to the presence of non linear local loads with the conventional control strategies. This issue is addressed by explaining a versatile harmonic load current feed forward control approach.