Control of SHEPWM for Grid-Connected Inverters in the Context of gRid Harmonics

With the large-scale grid connection of distributed generation systems, the performance of grid-connected inverters is seriously challenged by the non-ideal conditions at the common coupling point. Aiming at the problem that the distribution network connected to distributed generation often contains a large number of low harmonics due to the load influence, this paper analyses the influence of grid voltage on the grid-connected current of the inverter in distributed generation, proposes a selective harmonic elimination control method for the grid-connected inverter under grid harmonic conditions, and establishes a full-period asymmetrical SHEPWM harmonic compensation model based on the Fourier analysis and adopts the stepping Newton iterative method to The online solution of the model is implemented. The suppression of grid background harmonics and the elimination of integer times carrier band harmonics with high interference energy are achieved by precise control of the amplitude and phase of each harmonic in the AC side output voltage of the inverter. A complete simulation model of SHEPWM harmonic compensation is constructed in SIMULINK environment of MATLAB, and the simulation results are analyzed, and it is found that the harmonic content of the grid-connected current can be greatly reduced, so that the harmonics and the total harmonic distortion rate of the gridconnected current can meet the standard requirements (Abstract)