On-line monitoring of eigen-frequency and stability of power system by use of SMES

It is useful to grasp power system stability margin from on-line data in real time. We have proposed to estimate the system operating conditions from on-line data by use of superconducting magnetic energy storage (SMES) system. In this paper, we developed the proposed method to monitor the eigen-frequency of the power system in real time, which changes with time due to the system operating conditions (such as, generator output change), by use of a SMES and a lock-in amplifier. Basic experiments were carried out on an analogue-type power system simulator and a model SMES for the simulator. By use of the SMES, the eigen-frequency change according to the operating condition change was successfully measured, tracked and monitored on-line. The stability margin can be estimated by the monitored eigen-frequency. The availability of the proposed method is discussed on the experimental results.