Improved control in single phase inverter grid-tied PV system using modified PQ theory

Grid-connected reactive-load compensation and harmonic control are becoming a central topic as photovoltaic (PV) grid-connected systems diversified. This research aims to produce a high-performance inverter with a fast dynamic response for accurate reference tracking and a low total harmonic distortion (THD) even under nonlinear load applications by improving its control scheme. The proposed system is expected to operate in both stand-alone mode and grid-connected mode. In stand-alone mode, the proposed controller supplies power to critical loads, alternatively during grid-connected mode provide excess energy to the utility. A modified variable step incremental conductance (VS-InCond) algorithm is designed to extract maximum power from PV. Whereas the proposed inverter controller is achieved by using a modified PQ theory with double-band hysteresis current controller (PQ-DBHCC) to produce a reference current based on a decomposition of a single-phase load current. The nonlinear rectifier loads often create significant distortion in the output voltage of single-phase inverters, due to excessive current harmonics in the grid. Therefore, the proposed method generates a close-loop reference current for the switching scheme, hence, minimizing the inverter voltage distortion caused by the excessive grid current harmonics. The simulation findings suggest the proposed control technique can effectively yield more than 97% of power conversion efficiency while suppressing the grid current THD by less than 2% and maintaining the unity power factor at the grid side. The efficacy of the proposed controller is simulated using MATLAB/Simulink.