Stabilization of the KSTAR Power System for the First Plasma Operation

After more than ten years of construction, the Korea Superconducting Tokamak Advanced Research (KSTAR) device finally completed its assembly in June 2007. We conducted the first plasma operation from April 2008 to July 2008 and succeeded in the plasma generation in July 2008. The electric power system for the first plasma operation is made up of various electric devices, including 154-kV circuit-breaker systems, a 154/22.9-kV 50-MVA transformer, 22.9-kV circuit-breaker systems, and reactive power compensator (RPC) and harmonic filter (HF) systems. When the poloidal-field magnet power supplies were operated, the reactive power and harmonic currents (12n ± 1) were generated instantaneously in the KSTAR electric power system for the first plasma generation due to the characteristics of the KSTAR superconducting coils. The measured voltage drop and harmonics seriously affected the other experimental equipment as well. Therefore, it is important to compensate the reactive power and remove the harmonics with the RPC and HF system for the superconducting tokamak device. In this paper, we discuss the stability of the electric power system and the operational results of the RPC and HF systems during the KSTAR first plasma operation. Furthermore, the upgrade plan of the electric power system based on the KSTAR operation plan will be discussed.