Abstract: This paper introduces a distributed monitoring system based on C200Hα and KingSCADA industrial control configuration software, and its application in the monitoring system of a comprehensive power station—refrigeration station, heat exchange station, and circulating water station. The hardware structure, software composition, and PLC configuration of the system are described in detail. The specific communication methods and programming concepts and flowcharts of the lower-level software are also introduced. This paper further introduces the advanced control technology and requirements of the comprehensive power station, and a simple method for implementing constant pressure water supply. The system has been put into operation and has achieved good application results. Keywords: PLC; Configuration Software; Complex-station; Monitor System Abstract: This paper proposes a distribution monitoring system based on PLC-OMRON C200Hα and configuration software-KingView5.1, and its application in a complex-station, including a refrigeration station, heat-swapping station, and recycling water-supplying station, is demonstrated. The paper details the hardware structure, software configuration, concrete PLC configuration and communication mode, PLC programming method, and diagram flow of the distribution system. It also presents advanced control technologies and a simple and convenient way to achieve constant pressure water supply for complex-station applications. The monitoring system has been running smoothly for a long time. Key words: PLC; Configuration Software; Complex-station; Monitor System In large-scale machinery processing industries, especially the automotive industry, numerous energy stations and other stations are frequently used, such as refrigeration stations, circulating water stations, heat exchange stations, air compressor stations, and sewage treatment stations. Like vital organs such as the heart and kidneys in the human body, these systems play a crucial role in the supply, circulation, and recovery of energy (compressed air, hot water, high-temperature steam, etc.) in factories. Therefore, the monitoring, management, and control of these station systems have become an important component of factory automation (FA). Automatic monitoring and control of these stations can significantly save resources and labor. Consequently, automatic monitoring of these stations will be increasingly widely applied. This article mainly introduces the monitoring systems for refrigeration stations, heat exchange stations, and circulating water stations. 1. Integrated Station Process Flow The integrated station process flow diagram is shown in Figure 1: This station mainly provides users with cold and heat sources, primarily used in central air conditioning systems for theaters, hospitals, large office spaces, and constant-temperature factories. Chilled Water Monitoring System: This system focuses on monitoring the chiller, which is a Dalian Sanyo steam-type bromine chiller. This chiller has a built-in PLC and RC-232 serial port, which, after conversion to RS485, can easily communicate with the host computer, thus conveniently obtaining the chiller's operating parameters. The system assesses the user's cooling load based on the temperature difference between the chilled water supply and return water and the total flow rate, determining the number of chillers to operate and the valve sizes to ensure optimal use of the cooling source and achieve the best energy-saving and operational results. The cooling water monitoring system supplies cooling water to the chillers through cooling towers and pumps, ensuring sufficient cooling water flow. It adjusts the cooling water operation based on climate and cooling load, ensuring optimal system operation while maintaining the required cooling water temperature and flow rate. The heating monitoring system provides hot water to the central air conditioning system through heat exchangers. Its main task is to control the heat exchange process to ensure the required hot water temperature and flow rate. The system assesses the user's heat load based on the temperature difference between the hot water supply and return water and the total flow rate, determining the number of heat exchangers to operate and the valve sizes to ensure optimal use of the heat source and achieve the best energy-saving and operational results. The circulating water supply monitoring system, because heating and cooling cannot be used simultaneously, uses only one water supply system to provide heat and cold sources to users in winter and summer to save costs. Switching between the cold and heat sources is automatic via electric valves. This system is actually a relatively independent constant pressure water supply system. It mainly consists of a frequency converter and a PLC, and its electrical schematic diagram is shown in Figure 2. The frequency converter used is a Fuji G9 suitable for pumps, which controls five circulating water pumps using frequency conversion. Through the logic control function of the PLC, constant pressure and variable flow control of the entire water supply system is achieved. To ensure stable system operation, the entire system is equipped with multiple protection functions such as overcurrent, overvoltage, overload, and self-diagnosis. After receiving a start signal from the host computer or local unit, the system starts pump 1 for frequency conversion operation. The PLC controls the frequency converter to adjust the pump speed based on the received pressure and flow signals, keeping the water pressure in the water supply network constant. When pump 1 reaches the power frequency, if the water pressure in the network still does not meet the requirements, this pump is switched to power frequency operation, and the frequency converter switches to pump 2 for frequency conversion operation. If the water pressure still does not meet the requirements, the switching continues until the requirements are met. Conversely, if the water pressure in the pipeline exceeds the set value, the PLC controls the frequency converter to reduce the pump speed. When the speed drops to the set minimum frequency, the already operational pumps are automatically switched off according to the first-in-first-out principle, ensuring the pipeline water pressure remains constant. In this way, the five pumps operate in rotation, preventing any single pump from running continuously and extending the equipment's lifespan. This system can be satisfied by closed-loop PI control, with the PI algorithm implemented by the PLC: Ui = Ui-1 + ΔU = Ui-1 + K[Ei - Ei-1 + (T/Ti)Ei]. The integrated station monitoring system is composed of a distributed monitoring system using PLCs. The PLC acts as the lower-level computer, handling data acquisition, output control, and status judgment for each subsystem. The upper-level computer, an industrial computer from Advantech, receives the field data collected by the PLC and stores it in a dynamic database. It performs functions such as alarm generation, real-time curve analysis, historical curve analysis, system operation status analysis, printout, and controlling the operation status of each system according to the requirements of the control room personnel. The PLC used is the OMRON SYSMACα series C200HE, a mid-sized PLC with a moderate price and high cost-performance ratio. It features a robust instruction set with many special function instructions, a rich set of special function modules, and powerful communication modules, sufficient to meet the multi-level requirements of modern factory automation. The main system configuration is shown in Table 1: [align=center]Table 1: PLC Hardware Configuration[/align] This system uses a single-level network. Communication primarily employs an RS422 upper-level connection with an adapter structure. The network structure of the monitoring system is shown in Figure 3: Due to the use of a one-to-four communication method, addresses need to be set for the devices. Therefore, the lower-level PLC uses the RS422 standard. Each PLC is equipped with an LK202HOSTLINK module. The PLCs are connected via a three-port RS422 adapter, and then connected to the upper-level PLC's serial port via an RS422 to RS232 adapter. The HOSTLINK module has internal communication software; the communication protocol is fixed, and only a few parameters need to be set by the user according to the field application. The C200H-LK202 host computer connection unit has four parameter setting switches SW1-4 on its panel. SW1 and SW2 are used to set the device number (also called station number) of the host computer connection unit, with a value range of 00-31. SW3 selects the baud rate. SW4 is used to set the command level and parity format. All PLCs in the network transmit data through a shared LR area. In the LR area, each PLC is allocated a write area and several read areas. During data transmission, the PLC writes data to its assigned write area in the shared LR area, while other PLCs read data from the corresponding area in the LR area through the PLC link unit, thus enabling the PLCs in the system to exchange information. 3. System Software Design The host computer monitoring software utilizes KingView 5.1 industrial control configuration software. It can fully utilize the graphical editing functions of Windows to easily construct monitoring screens and display the status of controlled equipment in an animated manner. It has alarm windows, real-time trend curves, etc., and can easily generate various reports. It also has rich device drivers and flexible configuration methods and data link functions. The software treats each lower-level machine as an external device, and the connection function is completed step by step according to the prompts of the "Device Configuration Wizard" during the programming process. During operation, KingSCADA exchanges data with these external devices through drivers, including data acquisition and data/command transmission. Each driver is a COM object, which makes the communication program and KingSCADA software form a complete system, ensuring efficient operation of the running system and also allowing for system scalability. Its communication principle with the lower-level machine is shown in Figure 4. The communication between KingSCADA and the OMRON PLC uses the OMRON HOSTLINK communication protocol. KingSCADA communicates with the PLC through the serial port, accesses the relevant register addresses of the PLC to obtain the status of the devices controlled by the PLC or modify the values ​​of relevant registers. The KingSCADA monitoring software can also display process flow diagrams, real-time measured values ​​of various parameters, real-time modification of various parameter values ​​required by the lower-level machine, communication management between upper and lower-level machines, real-time fault alarm screens, real-time database and historical database management, system log reports, and various production reports. A network database is established on the main monitoring station, and various real-time data, screens, charts and other information from the process monitoring station are stored in the local network server. Dynamic web pages are generated using ASP technology and published in real time, enabling web browsing of on-site data and laying the foundation for comprehensive Intranet management of the factory in the future. The lower-level software design adopts a modular structure, with each module as a subroutine. According to the system function division, the program consists of multiple modules, and the program size of each module is not large, so the compilation, debugging and maintenance of the entire program are relatively convenient. The lower-level software module block diagram of each subsystem is shown in Figure 5: 4. Conclusion After careful design and debugging, the system has achieved good results in the actual operation of a large comprehensive station of Dongfeng Motor Corporation and has won unanimous praise from users. (1) The system has significant energy-saving effect, saving about 30% of electricity per day in winter and summer since it was put into operation. (2) The system has greatly reduced the difficulty of operation for operators, reduced the failure rate and the number of maintenance. (3) It can make reasonable use of equipment, improve the operating efficiency of the entire system and improve the service life of equipment. [References] Jiang Yi. 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