부산대학교 도서관

PV systems are increasingly connected to the power system, applying the increasing impact to the distribution grid, where single-phase sources and loads can lead to significant unbalance and cause significant interference to three-phase inverters. To ensure the proper operation of three-phase inverters, this paper studies the control system for string inverters under the unbalanced voltage and ensures the current quality. To control the positive sequence and negative sequence current simultaneously, a dual vector current controller is applied in this paper. The DC link voltage is controlled in the first stage. Besides, this paper uses a PI+R controller to reduce the second-order harmonic of DC link voltage. To verify the performance of these strategies, simulation results are provided.