Control of Grid-connected Inverters Under Unbalanced Voltage Sag

Grid-connected three-phase inverters using solar energy are commonly used in power systems due to sustainability and environmental friendliness. These inverters usually use the maximum power point tracker (MPPT) to extract the power from the solar modules and generate this power to the grid. If happening a voltage imbalance or voltage sag, these inverters need to support the power grid through generation of reactive power and operate the inverters in non-MPPT mode. This paper proposes a method to protect the inverter over-current and DC voltage in conditions of grid voltage imbalance. In the non-MPPT mode, the DC power controller is removed completely. This method does not require any additional hardware. The simulation results have confirmed the performance of the proposed technique.