A Fault Current Boosting Technique for Grid Connected Inverters

The increasing of inverter-based distributed generations impacts the power grid in many areas. One of the most important impacts is the effect in the protection system. In a conventional grid system, synchronous machines supply fault currents up to 4-10 times p.u. but the inverter fault current is limited by its control system to be only 1-1.2 times rated current. The setting of protective devices in the power system, such as fuses and overcurrent relays, are calculated from the conventional grid fault current thus they cannot accurately detect faults in the power grid. This paper proposes a control algorithm for boosting the fault current injected to the grid during grid fault for an LCL grid-connected inverter. The fault current magnitude will be more than 2 times its rated current while the output voltage is under the rated value. Simulation results will be presented by MATLAB Simulink.