Superconducting magnetic energy storage based dynamic voltage restoration strategy for unbalanced voltage sags

A dynamic voltage restorer (DVR) with superconducting magnetic energy storage (SMES) is presented in this paper, which protects sensitive loads from unbalanced grid voltage sags. Firstly, the schematic representation and general principles of the DVR are described. Then based on the load voltage oriented vector analysis, the voltage injection magnitude, load power swing and phase shift are discussed. In addition, a new concept of restoration techniques is put forward to inject minimum energy for DVR during compensation. Simulation analysis and experiment results of the DVR system, show that the proposed method could minimize the injection real power of DVR with given apparent power and the customer side voltage is restored effectively. ©, 2015, Editorial Board of Jilin University. All right reserved.