Abstract: Since the 20th century, ship automation has undergone a process from unit automation, unmanned engine room watchkeeping to full ship automation. In order to realize the reliable operation, control and management of ship power stations and improve the automation level of unmanned engine rooms, this paper designs a novel distributed integrated automation control system for ship power stations, which can increase the reliability and economic effect by using advanced industrial control technology , computer technology and network programming technology. Keywords: Ship Power Station; Control System; Distributed 1 Introduction With the rapid development of electronic technology, computer technology and network communication technology, ship automation and management are developing towards full ship automation, ultra-automation and full digitalization. Based on a careful study and reference to current advanced control systems, and considering the characteristics and latest developments of ship power plant control systems, this paper studies a new type of distributed integrated automation control system for ship power plants, using PCs and multiple OMRON PLCs as CPUs. 2 Overall Structure of the Power Plant Automation System 2.1 Composition of the Ship-wide Automation System The ship-wide integrated automation system studied in this paper is a distributed control system based on a microcomputer local area network, which is a specific application of industrial distributed control systems on ships. Figure 1 shows a schematic diagram of the composition of the ship-wide automation system. [align=center] Figure 1 Schematic diagram of the ship-wide distributed control system[/align] In the figure, C is the field (or process) control unit with a microcomputer or PLC as its core. They are geographically distributed in various control fields on the ship, each independently controlling one or more loops, equivalent to a subsystem. It includes the underlying control modules, intelligent terminals, automation instruments, etc. The monitoring and management level computer (operator station) is generally a high-performance industrial PC. Each control unit can work collaboratively with other control units at the same level, while also being monitored and managed by the host computer; multiple host computers can also be networked to form a networked information and management system. As shown in Figure 1, the ship's overall automation system generally consists of two levels of networks: a field control level network and a management level network. Their networking methods can be the same or different. They connect the two layers of the ship's distributed integrated automation control system: the process control level and the monitoring and management level. Each level is interconnected yet independent. Each level can be horizontally decomposed into several subsets, with each subset having similar functions. The amount of information transmitted between the monitoring and process control levels is small, but the real-time requirement is high; while the real-time requirement for data transmission between PCs in the monitoring and management level is lower, but the amount of information transmitted is larger, facilitating comprehensive ship-wide management. 2.2 Composition of the Power Plant Automation System The power plant automation system is part of the ship's overall automation control network. It is based on computer technology, providing centralized monitoring, operation, and comprehensive management of power plant information, while decentralizing the control functions of each generator unit. It fully follows the ship's distributed control model, encompassing the three major components of the control system: distributed control devices, centralized operation and management, and communication systems. Based on the actual configuration of the ship's power system: three generator prime movers, one operating during normal navigation and the other two on standby; two generators operating during port entry/exit and cargo loading/unloading, and one on standby. The distributed control devices of the power station automation system are three PLC systems, belonging to the process control level, serving as control and data acquisition units for the three generator sets respectively, employing Direct Digital Control (DDC), and acting as the interface between the distributed integrated automation control system and the production process. These distributed control devices are referred to as measurement and control units, directly completing functions such as data acquisition, regulation control, and sequential control of the production process. Their process inputs are sensor signals (such as thermocouples and RTDs) and switching signals, and their outputs drive actuators. The centralized operation and management part is handled by a PC, serving as the operating system station, used for monitoring and information management of the lower-level machines in the power station system. The communication part, OMRONPLCC20OH, is equipped with an RS-232C connector, allowing communication with the host computer via a communication program. In fully automatic control mode, through the communication module, the three PLCs are coordinated by the host PC to complete the control tasks of the entire power station. Figure 2 illustrates the relationship between the above three parts. [align=center] Figure 2 System Communication Network Diagram[/align] The power plant automation system uses data communication as a link to complete a series of tasks such as distributed process control, monitoring, and centralized information management, which is the advantage of the system. 3 Measurement and Control Unit Design 3.1 Measurement and Control Unit Hardware Configuration Block Diagram [align=center] Figure 3 Measurement and Control Unit Principle Block Diagram[/align] The measurement and control unit belongs to the process control level of the power plant automation system. It is directly connected to the sensors, transmitters, regulating mechanisms, and electrical switches of the diesel engine, generator, and power grid to complete the control process of the entire power plant. It can also communicate with the host computer, receive parameters and work commands transmitted from the host computer, and report the on-site work information to the host computer after sorting it out, and use it as the data source for display, alarm, and printing. The measurement and control units of the three generator sets are completely identical, including analog input/output, digital input/output, keyboard input, and sound alarm. Figure 3 is the principle diagram of the measurement and control unit. 3.2 Signals between OMRON PLC and Generator Sets Since the signals of each generator set are completely identical, only the input/output signals and power grid signals of one unit are listed here. (1) Signals related to the diesel engine: lubricating oil pressure, cooling water temperature, starting air pressure, and exhaust manifold temperature. (2) Signals related to the generator: generator winding temperature, generator voltage, current, active power, voltage frequency, and phase difference between generator voltage and grid voltage. (3) Signals related to the grid: grid voltage, total grid active power, total grid current, and grid frequency. (4) Control signals (analog and digital) output by the C200H measurement and control unit: diesel generator start-up, diesel generator shutdown, generator grid connection, generator grid disconnection, diesel generator acceleration pulse, and diesel generator deceleration pulse. The signals of the power station system are shown in Figure 4. [align=center] Figure 4 Signals between C200H and the power station [/align] 4 Design of the host computer management unit 4.1 Basic functions of the host computer management unit On the basis of the distributed control of the corresponding units completed by each measurement and control unit, the monitoring and management unit further monitors and manages the entire power station system. It will complete the functions of parameter display, meter reading, alarm, printing, and some process operations. The management of large systems is generally completed by one or more computers. Because the shipboard power plant automation system is a small system, only one PC is used as the monitoring and management computer, referred to here as the host computer. This PC can also be used for centralized monitoring and management of the entire engine room. The host computer centralizes the process parameter information, collects data from the measurement and control units and sampling devices of each unit, and displays process quantities, various control flows, trend curves, and changes some process parameters of the power grid and units (such as voltage and frequency setpoints) through simple operations. These are the display and operation functions of the monitoring and management unit, ensuring the high-efficiency operation of the entire power plant system. 4.2 System Configuration of the Host Computer The hardware and software design of marine microcomputer control systems has higher requirements and more stringent conditions than land-based systems, mainly in the following two aspects: First, ships sailing at sea are affected by wind and waves, and the hardware equipment is subjected to turbulence, vibration, and corrosion from sea wind and seawater; second, ships have strict requirements for course and speed when entering and leaving ports and sailing at sea, and any errors will cause major losses such as collisions and grounding. Therefore, marine microcomputers adopt highly reliable industrial control computers approved by ship inspection, and special measures must be taken to further improve reliability. The industrial control computer includes hardware and software parts. The hardware part includes the host (CPU, RAM, ROM) board, internal bus and external bus, human-machine interface, system support board, disk system, communication interface, input and output channels. The software includes system software and application software. 4.2.1 Hardware configuration of the host computer The host computer has both monitoring and management functions and rich graphic display functions. The detailed configuration is shown in Figure 5. (1) Host board The host, composed of components such as central processing unit (CPU) and internal memory (RAM, ROM), is the core of the industrial control computer. It performs numerical calculations, logical judgments, data processing and other tasks of the control system. (2) Internal bus and external bus The internal bus is the common channel for information transmission between the various components inside the industrial control computer. It is a collection of signal lines. This host computer adopts the IBM PC internal bus. External bus is a common channel for information transmission between industrial control computer and other computers and intelligent devices. Commonly used external buses include RS-232C serial communication bus and RS-485 serial communication bus. The host computer of this system adopts RS-232C serial communication bus communication mode. [align=center] Figure 5 Hardware composition structure of host computer[/align] (3) Human-machine interface The human-machine interface is a standard structure, that is, it consists of a standard keyboard, display and printer. (4) System support functions The system support functions mainly include the following parts: Watch timer: used for system fault self-reset, used to improve the reliability of the system. Power failure detection: when the AC power failure is detected, it can protect the site. (5) Disk system: uses general hard disk. (6) Communication interface: uses RS-232C standard serial communication interface. (7) Input and output channels: this refers to the signal transmission and exchange connection channel set between the host computer and the power station, which is completed by the intelligent interface board. It includes analog input and digital input. Its function is to convert the signals of the power station system into codes that the host can accept and recognize. The automated power station system outputs control and regulation signals to the PLC measurement and control units of each unit through the serial port, so there are no signals output from the interface board. 4.2.2 Software composition of the host computer The software is the program system of the host computer, which is divided into system software and application software. (1) System software: Windows 2000 real-time multitasking operating system is used. (2) Application software: The application software is a monitoring and management program developed for power station automation. These programs are jointly developed using Microsoft's Visual Basic 6.0 and ACCESS. The innovation of the author of this article: This article discusses the design scheme of the distributed integrated automation control system of the ship power station, designs the functions of the automated power station, realizes the multi-machine communication technology between the PC and multiple Omron PLCs, and compiles part of the monitoring and management software of the host computer. References: [1] Wang Weibing, Gao Junshan. Programmable Controller Principles and Applications [M], 1st edition, January 2002, 2000, Machinery Industry Press, 4-6 [2] Shi Yongxin. Distributed Control System GAC-16M for Ship Power Stations [J], Navigation Technology, 1999, 02 [3] Du Jun, Xu Yongfa, Li Gongxuan, Li Shijin. Research on Automation of Ship Power Stations Based on CAN Fieldbus [J]. Navigation Technology, 2003, 05 [4] Wang Jianfei. Ship Propulsion Monitoring System Based on Fuel Cell [J]. Microcomputer Information, 2006, 12-1: 18-19