Evaluating Reactive Power-Based Voltage Support for the Low Voltage Ride Through Capability of the Distributed Energy Resource

Most of the grid codes generally require the Distributed Energy Resources (DERs) in order to remain connected throughout short-circuit grid faults and to provide the grid voltage support through reactive power-based regulation via additional Reactive Current Injection (aRCI) during the Low Voltage Ride Through (LVRT). It has been found out that the X/R ratio of the DER connection affects the effectiveness of the voltage support in improving the voltage sags. In this paper, the theoretical analysis of the system's X/R ratio impact on the effectiveness of the investigated voltage support is given. Furthermore, with the help of a MATLAB Simulink-based simulation study, the theoretical analysis is verified. The research is meant to substantiate a clear understanding of the effect of low X/R ratio to the voltage support in improving voltage sag. Finally, the rising number of the DERs on the distribution grid has been linked to the weakening of the grid strength, which often causes the system instability following the post-LVRT state. From the simulation, it has been found out that on a weak grid, the instability during the post-LVRT period could be prevented through correctly adjusted reactive power-based voltage regulation.