Unbalanced voltages in three-phase power systems is a common perturbation propagated along the grid. Distributed Generation plants have gained widespread attention due to their capability to improve power quality in a distributed manner, including voltage unbalance mitigation. A conventional control strategy to command power plants during balanced grid voltages, is the use of power factor to inject/absorb reactive power depending on grid conditions. Advanced control strategies during unbalanced grid voltages can be selected prioritizing positive or negative sequence active and reactive power. This selection determines the voltage support service and therefore can improve the voltage profile, i.e. phase-voltages can be properly supported and voltage imbalance simultaneously corrected. Based on the definition of effective power factor in IEEE 1459 Standard, the reactive power needed for any control strategy is obtained and the resulting effects are described.