Coordinated Injection of Active and Reactive Currents for Voltage Support in Grid-Connected Inverters

Voltage support strategies in grid-connected inverters have been extensively studied, yet they usually induce frequent mode switching and power imbalance between DC and AC sides under different voltage sag depths. To address those issues, this paper proposes a voltage support strategy based on active and reactive currents coordinated injection. The AC voltage control loop with anti-windup and adjustable reactive current limit is complemented in the current control. Meanwhile the operating conditions are divided according to the maximum available active current reference and the optimal active current reference, which are used to adjust the limits of active and reactive currents. This strategy avoids frequent mode switching and achieves better voltage support under different voltage sag depths. Simulation results verify the effectiveness of the proposed strategy.