Voltage support control strategy of grid-connected inverter system under unbalanced grid faults to meet fault ride through requirements

摘要: Grid-connected inverter (GCI) has become the main interface for integrating modern power units, such as distributed energy resources, electric vehicles, microgrids and high voltage direct-current transmission systems. To proceed in this direction, study presents a novel support control strategy to enhance reliability stability of GCI during unbalanced grid fault conditions. The proposed simultaneously achieves multiple objectives faults; regulating phase voltages magnitude within pre-defined safety limits, increasing difference between positive sequence (PS) negative (NS) voltages, eliminating both active–reactive oscillations DC-link oscillations. Reducing active ensure an adjustable which result third-order current harmonic component at side. One contributions previous studies, reference reactive is computed online based on resistive–inductive impedance model sequences support. Another important contribution existing studies supply powers utility load. Detailed mathematical analyses are performed theoretically describe behaviour strategy. A comprehensive set results presented confirm theoretical solutions.