Comparative Analysis of the Fault Ride-Through Capabilities of the VSG Methods of Microgrid Inverter Control under Faults

Abstract

The Distributed Generators (DGs) based on Renewable Energy System (RES) lack the inertia (rotating mass) and damping features of conventional power system, where fossil fuel based synchronous generators are dominant. The consequence of insignificant inertia and damping on grid stability and dynamic performance is further compounded with growing intermittent RES introduction into the grid. The use of RES based converters with appropriate Virtual Synchronous Generator (VSG) control strategy offers the necessary inertia support which culminates exceptional grid stability enhancement. However, the existing VSG studies focused on inverters in steady-state and under balanced grid voltage without emphasis on VSG dynamic performance during fault and other transients. Conversely, under fault conditions, it’s imperative to investigate the dynamic performance of the VSG control strategies while ensuring the protection of inverters owing to their low overvoltage and overcurrent tolerance capacities. Consequently, this study investigated the two methods of Virtual Synchronous Machine (VISMA) and carried out a comparative analysis to observe how the two methods ensure the VSG-inverter’s sustained grid connection under grid fault. Fault-Ride-Through (FRT) is the ability of electrical generating units to remain grid connected in the brief periods of fault and after fault clearance. Conclusions are drawn as to which VISMA strategies provide a better performance in terms of fault ride-through capability, current-limiting and recovery from faults.