Current Limiting and Fault Ridethrough Control of Grid-Connected Grid-Forming Inverters I

A grid-forming inverter maintains its internal voltage phasor approximately constant in the sub-transient to transient time frame. However, maintaining the internal voltage phasor approximately constant will result in severe over-currents during short-circuit faults with the possibility of damaging the inverter hardware. Moreover, during a long-term delayed clearing fault that phase angle of a grid forming inverter might lose synchronism to the grid and the dc bus voltage might collapse, too. Therefore, advanced current limiting and fault ride-through controls must be implemented to limit the output current of a grid-forming inverter during faults and maintain its synchronism to the grid post fault. This panel will introduce the challenges faced by a grid-forming inverter during severe faults an discuss the advantages and limitations of different current limiting and fault-ride-through controls recently developed.