1. Introduction With social progress and economic development, the steel industry has experienced rapid growth. However, competition within the steel industry has also become increasingly fierce. How to remain competitive, reduce costs, and minimize pollution has become a primary concern for the steel industry. The Jinan Iron & Steel Group's gas-steam combined cycle power generation project emerged under these circumstances. Gas-steam power generation uses blast furnace gas and coke oven gas from Lichuan as energy sources, not only solving pollution problems but also increasing revenue, thereby reducing production costs. The Jinan Iron & Steel Co., Ltd.'s "Gas-Steam Combined Cycle Power Generation Project" is another large-scale energy-saving and environmentally friendly project undertaken by Jinan Iron & Steel in accordance with national industrial policies to accelerate its own development. Its main components include two combined cycle generator sets, each consisting of one PG6561B-L type gas turbine generator set (48 MW) matched with one mixed gas compressor, one waste heat boiler, and one steam turbine generator set (18MW), forming a "1+1+1+1" configuration. The ETS (Emergency Shutdown System) is crucial for the normal operation of the steam turbine. 2. Working Principle of the ETS System The combined cycle gas-steam power generation system purifies and mixes blast furnace gas and coke oven gas at a mixing station, then pressurizes them into high-temperature, high-pressure gas at a coal press before sending them to the gas turbine. There, the gas mixes and burns with blast furnace gas in the combustion chamber. This drives the gas turbine, which operates at 10 kV. The voltage is then stepped up to 110 kV via an 80 MVA main transformer and connected to the 110 kV Jinan power grid via a GIS switchgear. The total installed capacity of the generators is 2x66 MW, with a plant power consumption rate of 25% and a grid-connected power output of approximately 100 MW. The overall efficiency is close to 50%, resulting in significant economic benefits. The ETS system, working in conjunction with the TSI (Total Gas Separation System), monitors important turbine signals and ensures turbine safety. When parameters entering the ETS exceed their limits, the turbine inlet valves are closed, triggering an emergency shutdown. Figure 1 shows the flowchart of the combined cycle gas-steam power generation system. 3. System Hardware Composition 3.1 System Network Composition According to the overall power generation design requirements, the ETS system adopts a 100 MB fiber optic Ethernet (dual-network) architecture. Both networks operate simultaneously with seamless switching, and each node's function is relatively independent. It primarily completes real-time data acquisition and processing of the steam turbine, as well as fault alarm processing, and makes judgments based on standard values ​​to protect the steam turbine. The ETS system plays a crucial role in the normal operation of the steam turbine; therefore, a three-out-of-two voting method is used for logic determination, and reliable redundancy and hot standby are implemented for the controlled PLC equipment and network, giving the entire system high safety and reliability. The lower-level control system consists of four PLCs: the ETS system PLC, the SOE system PLC, and the communication system PLC. The upper-level monitoring system is connected to the engineering station through this network. [ALIGN=CENTER] Figure 1 Flowchart of Gas-Steam Combined Cycle Power Generation [/ALIGN] 1) Operator Workstation The operator workstation, also known as the HMI (Hardware Management Unit), mainly performs data display, equipment operation, fault information monitoring, and equipment management for various process equipment or processes. It collects and organizes real-time data on process and equipment status, then transmits it to the process automation level to complete fault alarms, processing, and display for each process and equipment. 2) Engineer Maintenance Workstation Equipped with one engineer maintenance workstation, it provides maintenance technicians with functions such as database, interface, and report modification and maintenance, as well as network monitoring and maintenance. The engineer maintenance workstation can also serve as a training workstation for operational process rehearsals and real-time training simulations for operators. 3.2 System PLC Control The entire system adopts CIMPLICITY PLC controllers from GE (USA), combining the advantages of advanced PLC and DCS hardware and software. CIMPLICITY PLC controllers have rich tools for process control system design, implementation, documentation, and maintenance, enabling integrated automatic control of the entire process and establishing an economical, enterprise-level system integration. According to design requirements, the ETS PLC system uses the S90-30 controller, as do the SOE system and PLC communication system. The ETS PLC system controller employs a redundant hot-standby structure, using the GENIUS bus to monitor field input/output devices. The system consists of field control stations, operator stations, and engineer stations, and contains a three-layer network structure (as shown in Figure 2). The bottom layer is a bus structure, called the RIO bus, connecting remote input/output devices; the second layer is a control bus, called the GENIUS bus, using a GE proprietary protocol for transmitting process data, information exchange, and control signals; the third layer is an Ethernet network, called the Elhelm network, using the general TCP/IP protocol for system management function exchange between engineer and operator stations, and data communication between the system and branch plant-level management. [ALIGN=CENTER] Figure 2 ETS System PLC Network Layer Diagram [/ALIGN] 4. Software System Composition 4.1 PLC Program Development Software The system's PLC program development software is CIMPLICITYME. This software is built on a Windows platform and developed using CIMPLICITYME configuration software. It utilizes the ladder diagram RLD programming language to complete various detection signal, GPS clock synchronization, and other logic control functions, as well as data communication functions between PLCs. 4.2 HMI Monitoring Development Software Traditionally, SCADA solutions involve a single host computer handling information exchange with one or more PLCs. This system's HMI uses GE's CIMPLICITY Workbench development system, which is based on a hybrid SCADA and C/S architecture. The ETS system consists of two operator stations, one for each of the two turbines. The operator stations primarily handle data read/write functions with the PLCs. The system consists of a database server, a web server, operator workstations, maintenance engineer workstations, printers, and network equipment. The operating system is Windows 2000 (Western language). The monitoring interface performs data acquisition, calculation, judgment, alarm and protection for analog, digital, pulse, and temperature signals, as well as protection information from the public system. It also performs sequence of events (SOE), report statistics, curve analysis, and issues commands to the field protection and control unit layer as needed to control and regulate electrical equipment. The system features a user-friendly, convenient, and aesthetically pleasing human-machine interface, and a secure, accurate, and reliable database, making it an ideal system for automating the electrical operation, monitoring, and management of power plants. 5. System Communication 5.1 TCP/IP Ethernet Communication The system uses fiber optic redundant Ethernet. The server, engineer workstation, operator workstation, programmable logic controller (PLC), and supervisory control system (SCADA) are assigned unique IP addresses. The CPU of the PLC control system uses the CMM Ethernet communication template of this station and the EGD broadcast method to send and receive information with other PLCs on the Ethernet via a switch. The supervisory control system (SCADA) sends and receives information with the engineering workstation and PLC system via Ethernet cards and a switch over Ethernet. 5.2 Modbus Plus Communication: Modbus Plus is a peer-to-peer communication network with functions such as I/O data communication, interlocking, data acquisition, program upload/download, and online debugging and monitoring. Its use greatly facilitates solving the problem of long-distance signal transmission from the field control station to the central control station. In this system's PLC configuration, a dedicated PLC device uses the Modbus Plus communication network to communicate with the gas turbine MARKV, realizing full-process monitoring of the entire generator set. 6. Key Technologies Based on the reliability, efficiency, and ease of use of the software, the public works intelligent control system adopts many new technologies: ① The supervisory control system adopts the currently popular Server/Client architecture, supporting the development of three-tier C/S applications for enterprises. ② Excellent data access technology, using Microsoft SQL Server to create the database and its front-end application. ③ OPC (OLE for Process Control) technology. Data is obtained from the RTDB by connecting to the OPC Server through the OPC communication manager. ④ Online diagnostics and alarm technology for field equipment. ⑤ Authorized access control technology. ⑥ GPS global satellite positioning control technology. ⑦ SOE sequential event recording control technology. 6.1 GPS Time Synchronization Function For power generation systems, time is a very critical display and control parameter. To ensure strict time synchronization, a GPS (Global Positioning System) clock synchronization device is used to synchronize the clocks of all PLCs and HMIs in the network. The clock is output to the units via serial communication or a pulse-per-second (IPPM) signal. [ALIGN=CENTER] Figure 3 GPS Clock Synchronization Implementation Mechanism Diagram [/ALIGN] Figure 3 shows the GPS clock synchronization implementation mechanism, which is divided into two synchronization methods. For the HMI, the GPS clock signal is acquired through RS232 serial port using C language programming to synchronize the clock with one host computer. The clocks of other host computers are synchronized with HMI-1 via Ethernet. The PLC uses pulse switching signals to acquire SOE event recording PLC (PLC-1). The PLC-1 implements the read and write functions of pulse switching signals through an application program to achieve clock synchronization within the PLC. For other PLCs, clock synchronization is achieved by receiving the clock signal from PLC-1 via Ethernet broadcast using EGD (PLC Data Communication). 6.2 Event Alarm Recording Control To ensure normal power generation, it is necessary to accurately record the operating status of the main equipment of the generator set at any time. Therefore, the system uses a dedicated PLC to record the operating status of the equipment, providing a basis for production and maintenance engineers. For this purpose, an automatic event recording program was developed. The control flowchart is shown in Figure 4. 7. Conclusion The ETS control system fully meets the requirements of the entire gas-steam combined cycle power generation project. Since its commissioning, the system has operated reliably, significantly reducing equipment maintenance, minimizing potential failure points, and improving work efficiency. Furthermore, due to the adoption of some advanced domestic and international technologies, the system is easily expandable and upgraded. As an important component of the entire gas-steam combined cycle power generation project, optimizing the control, equipment management, remote operation management, and setpoint management of the power plant has significant economic and social implications for reducing losses and ensuring the reliable, safe, and stable operation of the power plant. [ALIGN=CENTER] Figure 4 Event Alarm Record Control Program Flowchart [/ALIGN] This article is from "Energy Saving Innovation 2006 - Proceedings of the First National Electrical Energy Saving Competition"