Impedance Enhancement Method for Grid-Connected Inverter Using Delay Compensation Algorithm

With the high penetration of distributed energy resources (DERs) integrated into modern power systems, grid voltage distortions have become major problems that have severe impacts on the operation behavior and power quality of grid-connected LCL inverters. In recent literature, many research studies have focused on reshaping the inverter’s output characteristics using virtual impedance-based control methods to suppress the negative effects of grid harmonics and distortions. However, the existence of the discrete-time delay in the inverter’s digital controllers has severely degraded the performance of these virtual impedance-based methods. Therefore, an advanced impedance enhancement method using a modified discrete-time delay compensation algorithm is proposed in this article for grid-connected LCL inverters. In the proposed method, a one-beat lead observer is designed, analyzed, and integrated with the current controller so that the discrete-time delay can be fully compensated, and the impedance characteristics of the inverter can be improved. The effectiveness of the proposed algorithm is verified through numerical analysis, simulation on a MATLAB/Simulink platform, and experiments on an LCL inverter prototype.