Positive- and negative-sequence control strategy of grid-connected PV systems under balanced and unbalanced voltage sags

摘要

A positive- and negative-sequence control strategy, which is suitable for both balanced and unbalanced voltage sags, is investigated to improve the injection current quality of gird-connected photovoltaic (PV) systems under unbalanced voltage conditions. Under the control strategy, the fault current is limited without negative current injection and it helps enhance the low voltage ride-through (LVRT) ability. Simulations were carried out in the electromagnetic transient simulation platform PSCAD/EMTDC and the simulation results are verified using the field short-circuit test data recorded in a large-scale PV power plant with a total capacity of 850MWp.