1 Introduction
With the continuous development of "unmanned" (or minimally staffed) operations in reservoir water conservancy projects, higher demands are being placed on their automation technology. The rapid development of computer technology, information technology, and fieldbus technology has provided a vast space for the development of hydropower plant automation systems, both structurally and functionally. Reservoir water conservancy projects should become integrated systems combining computers, control systems, networks, and multimedia.
2 System Design
This project draws water from the Dahuofang Reservoir, supplying water to six cities—Fushun, Shenyang, Liaoyang, Anshan, Yingkou, and Panjin—through tunnels and pipelines in a closed-loop system. The total length of the water transmission pipeline is 259.13 km, with water intake points, an Anshan booster pumping station (including a distribution station), and five distribution stations in Fushun, Shenyang 1, Shenyang 2, Liaoyang, and Yingpan. Currently, water conservancy project data acquisition and monitoring control systems (SCADA systems) generally adopt an open, fully distributed, and hierarchical structure, with a dispatch center group, sub-center level, and field control unit level (Note: Local Control Unit, referred to as LCU in this article).
Based on the principles of functionality and cost-effectiveness, the project selected Rockwell ControlLogix series PLCs as the LC control core of the water conservancy engineering information automation system . This paper discusses the system composition and characteristics of ControlLogix series PLCs, as well as their system structure, functions, and applications in the water conservancy engineering information automation system. The system structure principle is shown in Figure 1.
2. LCU based on ControlLogix PLC
The Integrated Control Unit (LCU) primarily performs local data acquisition and monitoring functions for the monitored equipment, using a touchscreen as the local human-machine interface. Its design ensures that even when disconnected from the master station system, it can still monitor and control the relevant equipment locally. Once reconnected to the master station, it automatically obeys the master station system's control and management, making it a low-level control component in the water conservancy engineering information automation system. Raw data is acquired here, and all control and adjustment commands are ultimately issued from here; therefore, the LCU is a crucial and highly reliable foundational control device in the entire monitoring system.
This paper describes the implementation of a ControlLogix series PLC in an information automation system for a water conservancy project. The LC mainly performs the following functions: data acquisition (digital switch inputs, analog inputs, temperature inputs, etc.), equipment control (digital outputs, etc.), data communication (serial communication, Ethernet communication), and human-machine interface . The LC system structure is shown in Figure 2.
To improve system reliability and ensure safe operation in harsh environments, the LCU main control unit adopts a ControlLogix hot standby system and a redundant 1756-L63 system. Each remote I/O unit of the LCU is connected to the redundant CPU main controller via a ConnectNet bus. To further enhance reliability, the ConnectNet bus uses redundant media. The main control unit primarily consists of a 1756-L63 CPU, a ConnectNet bus module (CNBR), an Ethernet module (ENBR), and an intelligent communication management device. The remote I/O units primarily consist of a ConnectNet bus module (CNBR), digital input modules, digital output modules, analog input modules, and analog output modules.
In the above configuration, the 1756-L63 is the core of the control system. ControlLogix achieves outstanding performance in a simple and easy-to-use environment, setting an industry standard. ControlLogix controllers have a maximum storage capacity of up to 8 MB, supporting process-intensive applications and fast motion control applications. Controllers with different storage capacities can be selected according to application requirements. CompactFlash cards can be used for mobile program storage. Multiple processors, communication modules, and I/O can be used interchangeably without limitations. No processor is needed for I/O bridging and routing; as the system grows, control can be distributed to other racks via a network.
3. Conclusion
This automated system control scheme has been adopted by several large-scale water conservancy project information automation systems in China. From the system's daily operation, it is stable, accurately and in real-time reflects the operating status and parameters of water conservancy project equipment, and accurately and reliably controls field equipment. All performance aspects meet the requirements of water conservancy project information automation systems. Furthermore, the system is easy to maintain, reducing workload and production costs for the operation and maintenance of water conservancy project information automation systems, thus creating conditions for achieving an "unmanned" (minimum staffing) operation and management mode for water conservancy project information automation systems.
References
[1] Fang Huiqin. Computer monitoring technology and experiment of modern hydropower plants, 2004, 3
[2] Deng Li. ControlLogix System Practical Manual, 2008, 1
[3] Ab ControlLogix Selection Guide [4] ControlLogix User Manual
