Voltage Support Control Method Based on Grid Code under Unbalanced Voltage Conditions

Nowadays power generation is transitioning from conventional synchronous generators (SG) to inverter-based resources (IBR) based on renewable energy sources. These power plants are mainly connected to the power system through voltage source converters. Compared to synchronous generators, IBRs lack inertia during disturbances. Therefore, appropriate control measures must be implemented to prevent large-scale chain trips during fault conditions such as voltage sags. The traditional approach to raising voltage involves injecting reactive current proportional to the voltage sag. Current grid codes simply set the linear relationship between the voltage droop and the reactive current, consequently not providing the optimized voltage support in unbalanced voltage. Therefore, in order to utilize the grid code in unbalanced voltage conditions, the three-phase voltage must be included as a whole in the measured voltage fluctuation conditions. In this paper, propose a control algorithm for compensating PCC voltage under unbalanced voltage conditions.