A novel control scheme of 230kA DC power source using thyristor, Phase-shifting rectifier transformer and On-load tap changer

This 230 kA DC power source is composed of four set separated DC power in parallel operation. There are +3.75deg, -3.75deg, +11.25deg, -11.25deg phase shifting between each rectifier transformer and original source. Each set device mainly contains on-load tap changer, phase-shifting rectifier transformer and con-phase counter parallel rectifier. In this paper, a current control scheme is realized based on SIEMENS corp. product. According to the required function, the hardware is chose and described, and the software is designed and realized. The design control system is organized by current control level, logic control level and human level. The relation between these levels is determined. The system is validated by electrolytic aluminum plant. From the measured data, the current control precision can reach 0.1% in dynamic process. The rectifier efficiency is more than 97.5%. The whole control device's realized zero current changing on-load tap changer. This developed DC power source can utilize for electrochemical, electro winning, plasma torches etc