Coordinated LVRT Control with Current-Limited Reactive Priority Support for Three-Phase Distributed Generators Under Grid Voltage Sags

This paper proposes a coordinated low-voltage ride-through (LVRT) control framework for three-phase converter-interfaced distributed generation (DG) systems that integrates autocorrection droop control (AcDC) and Adaptive Current-Limited Reactive Priority Control (ACL-RPC). Key limitations of current LVRT control methods are addressed, such as weak and transient performance and adaptability problems due to the presence of post-saturation clipping, indirect current reference shaping, or discrete switching in LVRT current limiting techniques. The AcDC method alters the voltage reference in line with the severity of the voltage dip, while the ACL-RPC method imposes a rigid current limit and constructs the active and reactive current components in a flexible manner. The coordinated method of both approaches even enables the support of voltage with the network, the suppression of current transients, and the seamless control of current with no need for the estimation of network impedance or fault type resolution. The simulations and tests carried out show that the current limit, transient overshoot, and post-fault performance with respect to LVRT methods showed a marked improvement. The results also support the hypothesis that the three-phase converter-interfaced DG systems with the proposed methods offer improved LVRT performance, protection of the converter systems, and enhanced dynamic stability with respect to disturbances from the grid.