Tang Yuejin

Comparison of superconducting fault current limiter in power system

Due to its ideal electrical behavior, the superconducting fault current limiter (SFCL) has become one of the most important development trends of limiters in power systems. This paper summarizes the main electrical behaviors of SFCL, including the relationship between SFCLs working current and the quench current of the superconducting coil (SC), and the relationship between equivalent fundamental frequency impedance of SFCL and normal state resistance of SC. Operation losses and response time of SFCL are also discussed. The paper analyzes different influences of quench type SFCL and nonquench type SFCL on waveforms and total harmonic distortion (THD) of line current and node measurement impedance. Electromagnetic simulation is adopted to analyze the characteristics of the SFCL.

High temperature SMES for improving power system stabilities

Superconducting magnetic energy storage (SMES) system has been proven very effective to improve power system stabilities. It is realized with superconductivity technology, power electronics and control theory. In order to promote the application of such kind control device and to further investigate the properties of the controller, a detail mathematic model of such control device is developed. Based on the developed model, extensive analysis including time domain simulation is carried out to investigate the characteristic of the SMES to compensate the unbalanced dynamic active and reactive power of AC power system. The capability of SMES to increase power system transient and small signal perturbation stabilities are analyzed. A prototype SMES is developed, in which the conduction cooling and the high temperature superconductive techniques are used. The performance of the prototype is experimentally investigated in a laboratory environment. Very encouraging results are obtained. After a brief introduction of the SMES control system and the principle of its capability to improve power system stabilities, the details of the mathematic model, the theoretical analysis, the developed device and the experiment test results are all given in this paper.