Design of a Coupling Transformer With a Virtual Air Gap for Dynamic Voltage Restorers

Dynamic voltage restorers are devices inserted in transmission and distribution electrical grids to improve efficiently the power quality. The weak point of these series devices is the fault current protection of the voltage source converter (VSC). We propose a new topology of the coupling transformer to protect the VSC, by replacing the usual electromechanical bypass by an embedded magnetic one. In this paper, the design method and the experimental validation of a low-voltage coupling transformer with a magnetic bypass are detailed.