Abstract : This paper introduces the upgrade and transformation of the converter automatic control system in the steelmaking plant of Tianjin Iron & Steel Group. The Siemens S7-400 and WinCE systems were adopted, and the bus-type network was transformed into a high-speed fiber optic redundant ring network. This improved the stability of the converter system, reduced the failure rate, alleviated the labor intensity of on-site personnel, and created significant economic benefits. Keywords : Converter, frequency converter, coaxial cable, high-speed Ethernet, fiber optic redundant ring, automatic control system 1 System Introduction Since its commissioning in 1994, the electrical and computer control systems of the converter system in Tianjin Iron & Steel Group's steelmaking plant have undergone several upgrades. As of July 2005, a comprehensive upgrade and transformation of the converter system was completed, upgrading from the original Siemens S5 automatic control system to the current Siemens S7 automatic control system. At the same time, network construction was strengthened to achieve underlying interconnection of the converter automatic control system, laying a good foundation for the future overall network construction of the steelmaking plant. With the continuous improvement of the system, the degree of automation has increased, while the failure rate has significantly decreased, greatly reducing the labor intensity of on-site operators and maintenance personnel, and making an important contribution to the development of the steelmaking plant. 2. Composition of the Converter Automatic Control System Taking the No. 2 converter automatic control system as an example. 2.1 Power Supply Configuration of the Converter System Power supply is crucial to the system; a clear and correct power supply path is essential for system stability and safety. To reduce mutual interference between different devices, relatively independent power supplies are used for different devices as much as possible. Its configuration is shown in Figure 1. [b][align=center]For details, please click: Application of Siemens PLC in Converter Automatic Control System[/align][/b]