With the rapid development of Communication, Computer, Control, and CRT (4C) technologies, DCS (Distributed Control System) technology has made significant progress. It has moved beyond its ivory tower and is now widely used in new construction, expansion, and technological upgrading projects. For coal-fired power plants and many factories requiring flue gas treatment, electrostatic precipitators (ESPs) are crucial auxiliary equipment. Their self-contained control systems face the requirement of integration into the factory's DCS to control the dust removal equipment through a unified interface. Based on specific user requirements and incorporating current advanced technologies, we have developed and designed various interconnection methods between the ESP control system and the DCS, successfully applying them to specific engineering projects. This has achieved centralized management and distributed control, meeting the user's need for integrated management and control. This paper analyzes various interconnection methods and discusses the interconnection capabilities between the ESP control system and the factory's DCS system. 1. Hardwiring Method: This method directly connects the I/O and A/D points of the electrostatic precipitator control system to the DCS system via hardwiring. It is intuitive and simple, but the DCS system can only monitor the I/O and A/D points connected to it, and cannot penetrate to subsystems. For example, it cannot monitor the operating mode of high-voltage equipment, specific faults, rapping cycle, rapping conduction angle, etc. It uses more cables, making expansion and upgrades difficult, resulting in low efficiency and outdated technology. This mode is only suitable for networks with lower requirements for the DCS system. A high-voltage cabinet I/O and A/D contacts are provided: High-voltage control cabinet and DCS system interface table 2. Modbus_RTU Method This is a mode developed to solve the problem of implementing DCS control at the field control level. This approach uses an industrial PC as the host computer of the Intelligent Precipitator Computer Control System (IPC system) for electrostatic precipitators, with each high- and low-voltage control device acting as a slave device. The IPC system collects operating data and parameters from each slave device via communication and manages and controls their operation. Simultaneously, the IPC system communicates with the DCS host via Modbus_RTU, enabling the DCS host to monitor the high- and low-voltage equipment of the electrostatic precipitator. Through this method, the DCS can fully penetrate each subsystem, such as monitoring the operating mode and specific faults of high-voltage equipment, and monitoring the rapping cycle and rapping conduction angle. Modbus is a widely used communication protocol in industrial fields, employing a master/slave structure. In a control network, the master is generally unique, while there can be up to 255 slave devices, each with a unique address identifier. The DCS acts as the master, and the IPC system as the slave. They are physically connected via an RS485 bus, explicitly using the Modbus communication protocol and RTU transmission mode. The slave addresses and the communication ports and parameter configurations used by the IPC industrial control computer are defined. Detailed specifications for data transmission lists, including addresses, names, parameter ranges, and data widths, are defined according to the specific project. The IPC system returns the content of the corresponding data entry or performs the corresponding operation based on the start address and number of data points in the DCS message. Based on these requirements, a dedicated communication interface program between the IPC system and the DCS was developed to determine the communication port, receive interrupt requests from the DCS, and respond promptly. The DCS can then create an interface consistent with the entire system based on the returned data to monitor the operation of the electrostatic precipitator. During communication, the master sends Modbus messages, and the corresponding slave responds according to the address field in the message. A broadcast is sent to all slaves by setting the address field to zero. The protocol distinguishes different types of messages through command words. Each message has a checksum field for the receiving end to verify the message's correctness and integrity. A standard MODBUS message structure is shown in the example below. In numerous electrostatic precipitator projects, such as the Huangdao and BALCO's self-owned power plant in India, we customized the communication interface between the IPC system and the DCS according to user needs. This not only successfully achieved communication between the two systems but also provided a clear hierarchy and simple structure, meeting the practical needs of the DCS for unified management and control of boiler units and their auxiliary equipment. Furthermore, as long as both systems adhere to the Modbus standard protocol, they do not need to concern themselves with each other's system architecture or operating platform to easily achieve communication, realizing system independence. In practical applications, only one communication cable needs to be laid between the IPC system and the DCS, and a few communication cables between the IPC system and the electrostatic precipitator control system, requiring almost no construction time. During operation, the DCS host typically issues various query commands according to its needs. The IPC system receives and responds to message commands from the DCS through the communication interface program, analyzes the command category, and returns the operating parameters of the electrostatic precipitator to the DCS, thus achieving mutual communication between the two systems. The communication connection diagram is as follows: 3. OPC Interface Method This is a model that emerged based on the development of industrial Ethernet to resolve system integration conflicts between different software developers and hardware manufacturers. Ethernet has the advantages of low cost, high speed, system openness, and strong compatibility. The emergence and development of switching technology has enabled Ethernet to achieve real-time performance, becoming a deterministic network. This broke the traditional 5-4-3 principle, significantly increasing its scale and coverage, thus bringing a revolutionary change to the automation market. Almost all DCS suppliers provide products with industrial Ethernet interfaces, resulting in C/S, B/S, and OPC models. OPC stands for OLE for Process Control. It is based on Microsoft's OLE (now ActiveX), COM (Component Object Model), and DCOM (Distributed COM) technologies, and consists of a series of standard interfaces, attributes, and methods for process control and manufacturing automation applications. It adopts a client/server model, placing the task of developing access interfaces on hardware manufacturers or third-party manufacturers, providing it to users in the form of an OPC server. This resolves the conflicts between software and hardware vendors, completes system integration, and improves system openness and interoperability. OPC provides a common interface for data exchange between a wide variety of industrial process control devices, systems, and human-machine interface software. Its emergence has bridged the gap between Windows-based applications and field process control applications, and it has been established as a de facto global industry standard, serving as the default solution for industrial system interconnection, supported by process control equipment manufacturers and industrial control software developers. OPC can be applied not only to standalone systems but also supports communication between distributed applications on a network, achieving seamless integration and truly open communication between system software and devices. OPC currently has three main specifications: Data Access Interface Standard, OPC Alarms and Events, and Historical Data Access. The Data Access Standard includes two sets of interfaces: a Custom Interface and an Automation Interface. According to the specification, an OPC data access server consists of three layers of objects. At the top layer is the server object, which contains server information and acts as a container for group objects. In the middle layer are group objects, which primarily maintain their own information and provide mechanisms for containing and logically organizing data item objects. At the bottom layer are data item objects, which represent the connection between the server and the data source (hardware device) and have three attributes: value, quality, and time stamp. However, data items cannot be directly accessed by clients; all access to data items is achieved through the group object containing the data item. Furthermore, one OPC server can provide services to multiple OPC clients, and OPC clients can connect to different OPC servers, offering highly flexible connections. Based on the openness, interconnectivity, and other excellent characteristics of OPC, the IPC system adds the functionality of an OPC server. According to the data access interface specification, during the development and design process, the IPC system is treated as the server object, high-voltage control units and low-voltage control units (such as heaters and vibrators) as group objects, and current, voltage, temperature, and vibrating time as data item objects. These are then organically organized, and corresponding interface programs are written and provided to OPC clients. The network structure diagram is as follows: DCS system configuration software generally has OPC functionality. By following the OPC specification and utilizing the program interface provided by the OPC server in the IPC system, an OPC client can be easily designed, quickly connecting to the IPC system and effectively achieving information exchange between the two systems. Simultaneously, users can design display and operation interfaces for electrostatic precipitator equipment that suit their preferences within the OPC client, meeting the need for a unified human-machine interface layout for the entire system. The application of the OPC interface method has been implemented in power plants such as Liyujiang and Yushe, with good operational results. 4. Interface Method Based on Configuration Software This is the model we have developed in response to the increasing maturity of industrial control configuration software technology. Configuration software refers to specialized software for data acquisition and process control. It is a software platform and development environment at the monitoring level of the automatic control system, using flexible configuration methods to provide users with a general-purpose software tool for quickly building industrial automatic control system monitoring functions. It supports various industrial control equipment and common communication protocols, and provides distributed data management and network functions. It is a software platform tool that allows users to operate without changing the original code of the running program. Industrial control configuration software has gained widespread popularity in automation engineering because it eliminates a significant amount of tedious programming work during industrial control implementation. It resolves the long-standing contradiction between the lack of computer expertise among control engineers and the lack of on-site operational skills and experience among computer professionals, greatly improving the efficiency of automation engineering. With its rapid development, real-time databases, real-time control, SCADA, communication and networking, open data interfaces, and extensive support for I/O devices have become its core features, and it continues to be enriched with new content. Consequently, more and more users and design institutes are not only requiring DCS system suppliers to use third-party industrial control configuration software such as InTouch, iFiX, KingSCADA, and ForceControl, but also requiring process control equipment manufacturers, including those producing intelligent control systems for electrostatic precipitators, to use the same configuration software. Industrial control configuration software consists of two main parts: a system development environment and a system operating environment. Its development and design revolve around four main parts: the human-machine interface system, the PC-based control system (also known as a soft PLC or soft logic), the real-time database system, and the communication system. It can realize functions such as dynamic visualization of industrial processes, data acquisition and management, monitoring and alarm, historical data storage, and multiple redundancy. The network topology of the IPC system based on configuration software is as follows: The entire system consists of a DCS system industrial computer, an IPC system industrial computer, a PLC, a network bridge, a DAU, and field high and low voltage equipment. The PLC uses Quantum or Control Logix, S7-400 series, etc. The DAU data acquisition module is responsible for acquiring data from the field electrostatic precipitator high and low voltage equipment and communicates with the network bridge via Modbus. The network bridge is responsible for interpreting and converting Modbus protocol data and PLC data using NetLinx or Profibus. Quantum series PLCs have Modbus interfaces, so no network bridge is needed. The DCS and IPC system industrial computers work together as an OPC client/server through configuration software, thus forming a complete DCS control network system. To ensure system stability, dual-machine redundancy and dual-network redundancy technologies are used, achieving true redundancy. The IPC system uses configuration software, which greatly enhances the graphical function, enables online configuration modification, and provides highly flexible configuration, solving the problems of difficult expansion, upgrade, and maintenance of applications written in programming languages ​​such as Delphi and C++. In summary, while these implementation methods differ, each has its advantages. Hardwiring is intuitive and simple; Modbus_RTU enables communication with the DCS system at the field control level; OPC thoroughly solves the long-standing difficulties in communication and integration between different systems; and the interface method based on configuration software utilizes Modbus, OPC, PLC, and configuration software technologies to address users' configuration needs for different systems. It can be considered that these interconnection methods can basically meet the current needs of industrial automation and integrated management and control. Not only can electrostatic precipitator control systems enter the DCS through these methods, but other control systems can also apply their principles to specific engineering projects according to actual requirements, bridging the digital divide between different systems and enabling data access and monitoring of network systems such as DCS and SIS, thus achieving the requirements of a transparent factory. References: 1. iFiX 3.0 Chinese Manual 2. Xie Jianying et al., Microcomputer Control Technology, National Defense Industry Press, 2001 3. Ma Guohua, Monitoring Configuration Software and Its Application, Tsinghua University Press, 2001 4. Xu Lichen, Industrial Integrated Control Network Platform, Industrial Control Computer, 2003, 10 5. Zeng Yongji, Communication between AB PLC and Modbus Network, Microcomputer Information, 2004, 6