Identification design for dynamic voltage restorer to mitigate voltage sag based on the elliptical transformation

In this paper, a new identification tool for dynamic voltage restorer (DVR) is proposed to achieve flexible active and reactive power dispatch during voltage sags. The presented tool entirely relies on the theoretical analysis of the elliptical transformation, and identification marks are determined for different power injections by using one set of digital codes. Besides, two parameters are presented in the accurate mathematical description of the current references, which guarantee continuous power delivery by selecting the proper values. The chief advantages include the smooth transition state during changes in different power deliveries as well as the elimination of active and reactive power oscillations. Then, the characteristics of the identification tool corresponding to the different power dispatch are analyzed to reveal the feasibility of the given current references. Finally, experimental tests utilizing a laboratory prototype are used to verify the flexibility of the proposed control schemes.