Real and reactive power control of solar grid-tie inverter under distorted grid conditions

Due to increasing density of integration of distributed generation systems (DGS) to the utility grid, continuous power supply from DGS is being considered desirable during temporary grid faults, to provide support to the grid under conditions like voltage sags. Researchers have been focusing on improved topologies and control strategies in order to enhance the performance of solar grid-tied inverters, especially during grid faults. This paper presents a simple yet accurate control strategy for three-level four-wire grid-tie inverters for real and reactive power injection which operates satisfactorily under distorted grid conditions. Independent control of the input and output side is obtained by using two-stages, with boost converter obtaining maximum power from the solar panels, and inverter injecting this power into the grid with grid standards being met. A DC link balancing technique using proportional controller is also presented. A three-level neutral point clamped grid-tie inverter with the proposed control is modeled in MATLAB-Simulink platform and its effectiveness, in terms of accuracy of operation under non-ideal grid conditions and reduction in total harmonic distortion, is validated using the simulation results.