Optimal control of selective harmonic elimination in a grid-connected single-phase PV inverter

Photovoltaic system is one of the renewable sources of energy utilized with conventional systems to meet the increasing power demand. The topology considered is a single-phase grid-connected photovoltaic (PV) system in which the inverter unit plays an important role. Harmonic currents injected into the grid by a large number of PV inverters will downgrade the power quality of the grid and causes an increase in the total harmonic distortion (THD) at the output of the inverter. This paper focuses on the current control strategy adopted by the inverters for harmonic elimination and hence for the reduction of THD for ensuring high quality of the current injected into the grid. A control strategy based on proportional-resonant-integral (PRI) controller and their suitability for grid-connected inverter current control is presented. For selective elimination of dominant lower order harmonics in the output current an adaptive harmonic compensation technique using adaptive filter is proposed. The interaction between the adaptive filter and the PRI controller in the system is analyzed. To maintain the THD within permissible limits current controller parameters are optimized by using Genetic Algorithm (GA). The proposed system was simulated using MATLAB and the performance is analyzed and compared.