Control of three-phase inverter-based DG system during fault condition without changing protection coordination

Growing utilization of distributed generations in the power system may lead to protection problems. Therefore, in the conventional methods, DGs should be disconnected from the grid in the fault condition. In the case of high penetration of DGs, this strategy leads to voltage sag problem. In this paper, the inverter based DGs are properly controlled in the fault condition instead of disconnecting from the grid. This approach is called fault ride through strategy. The simulation results show that the fault current is kept in the desired range by using the proposed algorithm and the protection coordination before connection of DG remains intact even after the connection of DG. In addition, the voltage sag is improved due to DGs reactive power injection during the fault condition. Moreover, this method has not any additional cost because the proposed control strategy is carried out on the interfaced inverter and there is no need to use additional elements.