A Transformer Inrush Reduction Technique for Low-Voltage Ride-Through Operation of Renewable Converters

The low-voltage ride-through (LVRT) capability is a critical requirement of grid-connected converters of renewable energy resources to uphold the stability of the power system. The step-up transformer that connects the power converter to the grid is exposed to sudden voltage changes throughout the LVRT, and the resulting magnetic flux deviation often leads to severe inrush current when the grid fault clears. The inrush current exerts significant mechanical forces in the transformer and damages its insulation. This paper proposes a control method of the power converter to reduce the risk of inrush current by mitigating the magnetic flux deviation during the LVRT operation. The proposed method also manages the output current of the power converter within the capacity of semiconductor devices to reduce their stress while performing the proposed flux compensation and other LVRT operations. The reliability of the power converter and the transformer can be improved by the proposed control method.