Coordination optimization control of DC component and harmonics for grid-connected PV inverters

Grid-connected inverters (GCIs) have been extensively adopted in distributed renewable energy systems. However, due to the asymmetrical gate-driving signals, imparities of the power semiconductors, and unbalanced grid voltage, etc., the grid current contains DC components which are detrimental to the grid. Furthermore, due to the nonlinear loads in the grid, the grid current may also contain harmonics. As a result, power quality of the grid current is degraded. IEEE 1547-2003 has specified the maximum DC component and harmonics contents of the grid current. In this paper, a repetitive controller (RC) for DC component compensation is put forward at first, then, a Discrete-Fourier-Transformation (DFT)-RC controller is presented for harmonic elimination. Considering DC components and harmonics may coexist in GCIs in utility, a coordination optimization control scheme utilizing Weight Factor Distribution Optimization Method (WFDOM) is introduced. The proposed method is realized by adaptively allocating the weight factors for DC suppression controller and harmonic elimination controller according to their relative deviations. Simulation and experimental results show the feasibility and correctness of the proposed method. The proposed method can applied to high power quality PV power generation system.