A Full-Feedforward Technique to Mitigate the Grid Distortion Effect on Parallel Grid-Tied Inverters

In this article, a novel full-feedforward (FF) technique is introduced to lessen the effect of grid voltage distortion on injected current from the multiparallel grid-tied inverters. In this technique, the feedforward transfer function is applied to only one of the system inverters known as the target inverter. Hence, the investment cost for designing and implementing the FF technique is remarkably reduced. The proposed technique is based on introducing a virtual negative admittance at the target inverter to cancel the total parallel admittance of the system. Moreover, the reasons and conditions of instability, caused by the conventional FF techniques, are fully explored in this article. Then, by modifying the conventional FF techniques, a feedforward transfer function is proposed, which guarantees the strong dynamic performance of the system. Ultimately, an additional solution is devised to ensure a desirable grid voltage harmonic rejection ability of the proposed FF technique. Simulation and experimental results verify the validity of the proposed FF technique for a system consisting of two identical parallel grid-tied inverters.