A Low Voltage Ride Through Control Method Based on a Virtual Impedance for a Grid Forming Inverter

Abstract

Grid forming inverters are expected to be installed in the utility grid in the near future, because they can provide inertia and short circuit capacity that are likely to decrease due to abolishment of thermal power plants. Also, these inverters have the advantage of enabling stand-alone operation for microgrid or business continuity plan. Since a conventional grid following inverter controls its output current directly, it is easy to prevent overcurrent in an event of a grid fault. On the other hand, a grid forming inverter works as a voltage source, therefore it is a challenge to limit its output current. This paper provides a low voltage ride through control method for a grid forming inverter, which is based on a virtual impedance. It realizes reliable current limitation and stable operation. The effectiveness of the proposed control method is verified by EMT simulation.