Reactive power injection strategies for three-phase four-wire inverters under symmetrical voltage sags

Current grid requirements tend to change in near future to accommodate more distributed generation units in the distribution power system without impairing its power quality. It is expected that the generators remain connected during voltage sags and provide ancillary services, such as reactive power injection, ensuring the operational stability of the electrical system. This work explores strategies for reactive power injection of three-phase four-wire distributed generation systems using natural (abc) coordinates. Constant current peak control, constant active current control and constant average active power control strategies are addressed in a grid-tied inverter under low-voltage ride through conditions. The design and implementation of the proposed power injection strategies are discussed and their effectiveness and technical viability are analyzed through computational simulations.