Combining with the process characteristics of flue gas desulfurization system in thermal power plant, the specific scheme and communication mode of control system using AB_ControlLogix 5000 Series PLC are put forward. The controller of the control system adopts redundant configuration, and the network configuration adopts its typical ControlNet and EtherNet modes. The signal transmission between different controllers is changed from traditional hard wiring to control network transmission, which not only reduces the cost of control system card, but also facilitates the centralized management of equipment. This paper focuses on how to realize communication control among three sets of redundant ControlLogix 5000 controllers in desulfurization system through ControlNet network. With the implementation of the new Environmental Protection Law, the environmental protection requirements are becoming higher and higher. Thermal power enterprises have formulated a series of measures to reduce pollutant emissions.
The desulfurization and denitrification systems are almost as important as the three main engines. The reliability of the system operation is directly related to the environmental protection parameters. The automation level of the control system is an important part to ensure the reliable operation of the system. Part. Although the automation level of DCS is greatly improved, from the point of view of control points and economy, many power plants still use PLC as the main control unit and then bring it into the centralized monitoring of auxiliary control network of the whole plant, which not only ensures reliability, but also greatly reduces the cost of the system.
The desulfurization system in our factory is divided into No. 1, No. 2 and sharing system in terms of process design.
The control system is also divided into three sets of independent redundant control mainframes according to process design. Combining with the actual situation of our plant, the specific design scheme of the hardware configuration and software configuration of the desulfurization control system and the method of realizing the functions of each module are given. The field operation results prove the validity, reliability and economy of the design scheme.
1756-RM. Hot standby redundant module. Realize dual CPU hot standby redundancy.
After the hardware configuration is completed, RSNetWorx software is used to configure the control network, and the hardware system can run. The control system software chooses a series of products developed by Rockwell Company matching hardware: RSNetWorx, RSLink, ControlLogix 5000, etc. RSNetWorx is used to provide design and configuration management services for ControlNet network, and to make network planning, so as to achieve the best application effect. RSLink is a device driver software running on the computer. It can provide perfect communication service and provide the underlying driver connection for a variety of Rockwell software applications.
RSLink is the underlying platform for Rockwell software applications to run normally. ControlLogix 5000 is a program development software. It runs on ControlLogix 5000 controller. It can provide four programming modes: text, ladder diagram, function block diagram and sequential function diagram to realize the requirements of different control modes. ControlNet network adopts the general industrial protocol (CIP) which is widely used in the field of industrial communication.
It adopts the advanced producer/consumer network model, optimizes the utilization of broadband to the maximum extent, and can form a multi-master, master/slave, and peer-to-peer communication structure.
The communication between different redundant controllers introduced in this paper is to use 1756-CN2R special communication module to complete data exchange and transmission. Data Type: TRANSFER#2PLC and public PLC establish labels according to the above methods, but two points need to be noticed: First, when establishing labels in each PLC program, it must be one-to-one correspondence, that is, the PLC has a type of Produced send data label, and the other two PLCs should have a type of Consumed receive data label corresponding to it, and vice versa. 2. The data type and RPI of sender’s data label and receiver’s data label must be consistent in PLC program.
This example includes 40 floating-point numbers, 40 long shaping, and 64-bit arrays. To assign its current value to FGD_10.DIN[0], thermostatic element and reset automatically when it exceeds the set value. Then compared with the values of FGD_20.DIN [0] and FGD_A0.DIN [0], the mismatch is considered abnormal communication. After the above work is completed, the logic is downloaded to the CPU and the controllers are put into normal operation. In the logical configuration, the program can be written according to the communication needs. When programming (taking #1 PLC as an example), the data to be sent is transmitted to the corresponding unit of FGD_10 corresponding array, and the corresponding units of FGD_20 and FGD_A0 can receive the data in time; similarly, the data sent by the corresponding CPU can be read from the corresponding units of FGD_20 and FGD_A0, and the data received will be processed in the next step. So far, the communication function of the control network has been realized.
The long field operation shows that the communication mode is real-time and reliable. Through the above hardware selection, communication network configuration, software settings and the compilation and operation of PLC program, the reliable transmission of information between different controllers of the desulfurization system in our plant is realized, and the performance is superior.
Rockwell ControlLogix 5000 Series PLC has been widely recognized and applied in auxiliary control network of domestic power generation enterprises because of its flexible hardware configuration, comprehensive control function, excellent process control, fast response, perfect instruction system, powerful software development function and friendly man-machine interface. Therefore, the realization method of communication control mode of control network introduced in this paper has important and practical significance, and provides a design idea for the realization of centralized monitoring and management of decentralized control in auxiliary control network of power generation enterprises.