PLC in the ice storage central air-conditioning system of control1 IntroductionIn PLC in 30 years which developed, it passes through develops unceasingly, already could unify simulates I/O, the network corresponds as well as uses new programming standard like IEC 61131-3. However, engineers only must use digital I/O and few simulations I/O number as well as simple programming skill on potential 80% industrial application.PLC has been widely used in all industrial sectors. According to "The United States market information" World PLC and software market report, in 1995 the global software PLC and its economies of scale of about 5 billion US dollars [5]. As electronic technology and the development of computer technology,Because uses traditional the tool to be possible to solve 80% industrial application, like this intensely needs to have low cost simple PLC; Thus promoted the low cost miniature PLC growth, it has the useful trapezoidal logical programming digital I/O. However, this has also created the discontinuity in the control technology, on the one hand 80% application need to use the simple low cost controller, but on the other hand other 20% application then have surpassed the function which the tradition control system can provide. Engineer is developing these 20% application to need to have the higher circulation speed, the senior control algorithm, the more simulations function as well as can well and the enterprise network integration.In 80 and the 90's, these must develop "20% application" engineers had considered uses PC in the industry control. PC provides the software function may carry out the senior task, provides the rich programming and the user environment, and the PC COTS part enables control engineer the technology which develops unceasingly to use in other applications. These technologies including floating point processor; High speed I/O main line, like PCI and ethernet; Fixed data memory; software development kit. Moreover PC also can provide the incomparable flexibility, highly effective software as well as senior low cost hardware.Ice thermal storage air conditioning is the central power grid could be redundant-night ice electricity in the form of cold storage, in the daytime peak hoursof electricity to provide air-conditioning services melting ice. As most parts of our country at night than during the day much lower price, using ice cold storage central air-conditioning can greatly reduce user operating costs.Ice storage central air-conditioning system configuration of equipment than conventional air conditioning system to increase some, require a higher degree of automation, but it automatically to meet the requirements of the air-conditioned buildings all day every day under the conditions of the energy he has exhausted all, the biggest limits to save operating costs.the PLC functions are greatly enhanced, with the following characteristics:(1) high reliability. PLC benefited from the high-reliability hardware and software on a series of anti-jamming measures and the cycle of its special scanning methods of work.(2) with rich I / O interface module. PLC for different industrial field signal and the corresponding I / O modules and industrial devices or equipment at the scene of a direct connection. In addition to improving performance, it also has a variety of man-machine dialogue interface modules to the industrial composition of local area networks, it also multiple communications network interface module.(3) modular structure. To meet the needs of various industrial control, in addition to a small PLC unit, the vast majority of PLC are modular structure. PLC various components, including the CPU, power supply, I / O, etc. is modular in design from the rack and cables will connect each module, the system's size and function in accordance with the needs of users of its own portfolio.(4) easy to learn programming. Most of the PLC programming relay control circuit similar to the ladder diagram form, the user, do not have computer expertise, it is easy to general engineering and technical personnel understand and master.(5) Installation is simple and easy maintenance. PLC does not require specialized equipment room in a variety of industrial environments can be directly run. Various modules are run and fault indication devices, user-friendly understanding of the operation and find fault. The modular structure, so any failure of a module, users can replace the module, allowing the system to rapidly resume operation.Second, the characteristics and Application of industrial PC2 control systemThe control system consists of the crew (Floor Control Workstation) and PC (central management workstation), with the crew using programmable logic controller (PLC) with the touch screen, PC using industrial-grade computers and printers, system configuration necessary if the annex communications equipment interfaces, network interface cards, modems and so on, to achieve the parameters of the storage system and intelligent automatic operation.Under the crew at the scene and touch-screen systems can control, parameter settings and data. PC remote management and print, it contains the crew and all of the features touch screen. Following the system as a whole crew of industrial programmable logic controller as the core, to achieve automatic control. Control equipment and devices including: detection sensor components, electric valves, converter, etc..Under the 2.1-Systems (Regional workstations)2.1.1 TP21 touch screenTP27 used as a color touch-screen operator panel, completely replace conventional button, lights device, the control cabinet interviewed more tidy. Moreover, TP27 touch screen at the scene showed that the state can be realized, system settings, mode selection, parameter setting, fault recording, record load, time-of-day, real-time data, load curve and reporting statistics, and other functions, Chinese intuitive and friendly user interface.2.1.2 SIEMENS PLCSIMATIC S7-300 Series PLC applied to all walks of life, all kinds of occasions in the detection, monitoring and control automation, its powerful features to both operate independently, or linked to a network able to achieve complex control functions.The product features photoelectric isolation, and high electromagnetic compatibility; high industrial applicability, allowing the ambient temperature of 60 ℃; has a strong anti-jamming and anti-vibration and impact resistance, in the harsh environment of the work has been widely applications.I also means freedom of communications S7-300 PLC, a very uniquefeatures, it makes S7-300 PLC with any communication protocol can open other equipment, communications controller, or PLC S7-300 can be defined by the users themselves communications protocols (for example ASCII protocol), baud rate of 1.5 Mbit / s (adjustable). Thus the scope of the communications can be greatly increased, the control system configuration more flexible and convenient. Any serial interface with peripherals, such as: printer or bar code readers, the drive, a modem (Modem), the upper PC can be connected to the machine. Users can program to develop communication protocol to exchange data (such as: ASCII character code), RS232 interface with the equipment available PC / PPI free cable linking communications communication.Chip and Chip Holderslntegrated Circuis are usually called Ics or chips. Thay are complex circuits, which have benn etched onto tiny chips of semiconductor(silicon). The chip is packaged in a plastic holder with pins spaced on a 0.1(2.54mm)grid, which will fit the holes on stipboard. Very fine wires inisde the package link the chip to the pins.1)Pin numbersThe pins are numbered anti-clockwise around the IC(chip) starting near the notch or dot. It shows the numbering for 8-pin and 14-pin Ics, but the principle is the same for all sizes.2)Chip holders(DIL sockets)ICs(chip)are easily damageded by heat when soldering and their short pins cannot be protected with a heat sink. Instead we use a chip holder, strictly calleda DIL socket(DIL=Dual In-Line), which can be safely soldered onto the circuitboard. The chip is pushed into the holder when all solding is complete.Chip holders are only nedded when solding so they are not used on breaboards.Commercially produced circuit boards often have chips soldered directly to the board without a chip holder ,usually this is done by a machine which is able to work very quickly .Please donnot attemp to do this yourself because you are likely to destory the chip and it will be different to remove without damage by de-soldering.3)Removing a chip from its holder4)If you need to remove a chip it can be gently prized out of the holderwith a small flat-blade screwdriver. Carefully lever up each end by inserting the screwdriver blade between the chip and its holder and gently twisting the screwdrive. Take care to statre lifting at both ends before you attempt to remove the chip,otherwise you will bend and possibly break the pins.5）Bipolar Integrated Circuits MOS Integrated CircuitsHistorically, bipolar Integrated Circuits used to be much more popular than MOS Integrated Circuits,particularly for small-sace logic Circuits. There were two major reasons for this: first, bipolar-junction transistors originally could be manufactured more reliably than MOS transistors,and second , they were faster, As the reliabitity of MOS transistors improved, and as integrated Circuits became more complex , which made the lower power and small size of MOS logic more important, the popularity of BJT logic decreased, however, BJT technology is still popular for the highest frequency logic circuits.When the PC offline, under the control of the next crew, the entire system can operate normally.PC System 2.2 (central management workstation)PC 2.2.1PC that is by control centre, mainly by the PC and laser printer components, SIMATIC WINCC software platform used by the entire Chinese user interface, friendly man-machine dialogue. Management and operation, can be observed by PC-display all kinds of information to understand the current and previous controlled the entire ice storage system and the operation of all parameters, and equipment through the mouse print management and the implementation of tasks.2.2.2 WINCC software platformWINCC software in the field of automation can be used for all operator control and monitoring tasks. Process control can be in the events clearly show, can show that the current state records in accordance with the order, all the recorded data can be displayed or select summary form, or may be required for editing, and output print statements and trends .WINCC able to control the process of the critical early stages of the report, and the signal can be displayed on the screen, and can also use voice demonstrated. It support the use of on-line help and operational guidelines to eliminate fault. WINCC a specialized workstations can be used to control the process so that the important process information is not shielded. - Aided software strategy assurance process is not illegal access, and provide for the industrial environment no wrong in the operation.WINCC is MICRSOFT WINDOWS98 or WINDOWS NT4.0 operating system, running on a PC object-oriented class 32 applications, through Windows OLE and ODBC standard mechanism, as an ideal communications partners to enter WINDOWS world, and therefore can be easily WINCC to integrate a company-wide data processing system.3 ice storage system control3.1 control objectives, scope and mainly controlled equipmentStorage Control System control purposes: Through the refrigeration host, ice storage devices, plate heat exchanger, the system pumps, cooling towers, piping system regulating valve control, ice storage system adjustment of the status of the operation mode, in the most economical circumstances to the terminal to provide a stable water supply temperature. At the same time, improve the level of automation, improve the management efficiency and reduce labor intensity management.Control of the ice storage system, including the entire state of the parameters, equipment status and control, the main control equipment: duplex status console, electric valves, cooling towers, cooling water pumps, ice storage devices, the primary glycol pump, plate heat exchanger , sub-glycol pumps.3.2 controlControl functions include the ice storage system stability, and economic operation of the required functions.3.2.1 status of the conversion functionDepending on the season and machinery operation, automatic control system with the following conditions conversion functions:A) duplex host ice conditions at the same time cooling mode; b) duplex status of a separate ice-making mainframe model; c) ice-storage devices and host jointcooling mode; d) of ice-melting separate cooling mode; e) for the console alone Cold model.3.2.2 The status of the start-up and shutdown, display and alarm functions FaultControl system according to the chronological layout with load forecasting software, mainframe and external control refrigeration equipment start-up and shutdown of the surveillance equipment and the number of working conditions and operating parameters, such as:-- Commitment refrigeration console, status and fault alarm - refrigeration mainframe operating parameters - the protection of water cooling host - host for refrigeration / return water temperature, pressure telemetry and display; - Commitment chilled water pumps, status and fault alarm -- glycol pump start-up and shutdown, status and fault alarm - start-up and shutdown cooling pumps, status and fault alarm - bypass pipe pressure measurement and display of pressure - the cooling tower fan Commitment, status and fault alarm;-- For the cooling tower / backwater temperature control and display; - for / return water temperature, pressure telemetry control and display - the import and export side of plate heat exchanger temperature control and display; - ice storage devices import and export control and telemetry temperature display; - chilled water backwater flow control and display; - electric valve switch valve position adjustment and control and display; - outdoor temperature and humidity control and telemetry showed - ice storage and display of measurement - the end of cold load control.3.2.3 Data recording and printing functionsControl system for the monitoring of the needs of the trends point to the entire record, the control system can be the load throughout the year (including the maximum daily load and the load throughout the day) and equipment uptime as tables and charts record for users . All monitoring points and the calculated data can be automatically print regularly.3.2.4 manual / automatic conversion functionFlexible control system configuration manual / automatic conversion function.3.2.5 optimized control functionAccording to outdoor temperature, weather, weather trends, the historical record, such as mainframe data automatically select the priority or ice-melting priority. In the end load to meet under the premise of the daily use of the cold storage End, as far as possible to run mainframe. Give full play to ice cold storage system advantages, saving operating costs.3.2.6 automatic functionalityFrom the PC system can work, in accordance with timetable for the automatic ice-making and control system operation, the conversion status of the system for automatic fault diagnosis, and remote alarm. Touch screen display systems operations, processes, each node parameters and operating records, the police records.3.2.7 holidays function setAccording to the timetable system can be run automatically, but also to pre-set holidays, and ice control certificates and certificates of ice time, the system does not require the holidays when the supply of cooling air-conditioned places to stop.3.2.8 operating under the crew functionLower-color touch-screen operator interface Figure 1.Under the crew operating functions are as follows:A) human-computer dialogue. Operation can be carried out through the touch panel interactive, user interface completely in the culture, with tips, help, parameter settings, key settings, fault enquiries, history and so on.B) system settings. Including operation password settings, run setup, operation of the timetable set record overflow processing, automatic / manual / test selection, holiday settings, the system parameter settings (including the junction temperature, pressure, the media flow, reservoir ice, ice rate, the ice-melting rate of valve opening, the terminal load.)C) fault records, running records, historical records.Remote Control 3.3Control system through the telephone line or broadband network, and expert system connectivity, the system operation control, parameter changes, such as dataacquisition, allowing the system to constantly improve and upgrade version of the software, allows users to get a better service. The purpose of the Remote Control users can PSTN (Public Switched Transport Network) on the remote frozen station at the remote monitoring. It may be remote debugging, remote monitoring and timely online maintenance, and so on, thus greatly mitigate the intensity of the work, lower cost of the project.3.4 control system expansionControl System Design friendly interface, PLC and touch screen can be extended, the content can be extended, parameters can be modified through the 485 communication interface or communications protocol BAS cold storage and ice-controlled system integration, savings investments, facilitate management. Centralized control system, reducing the dynamic counter area, and also allows the dynamic counter models reunification, the same style, same size. Extended control system are as follows:A) sewage pump control; b) wind, ventilation control; c) live pump regulator control; d) regular-pump operation, detection, alarm; e) leaching pump regulator control; f) construction of contour night lighting control ; g) measurement with low switching state detection, alarm.4 ConclusionPLC through ice storage air-conditioning systems in the promotion of the use of PLC verify the reliability of the system features to ensure the safe operation of the system and effective energy-saving, but also for building control equipment selection system controller provides a new way of thinking. I believe in the near future, a growing number of PLC systems in the ice storage air-conditioning systems in the use of the increasingly mature, in buildings and plant control systems will also play an active role.PLC在冰蓄冷中央空调系统控制中的应用1 引言在PLC被开发出来的三十年里，它经过不断地发展，已经能结合模拟I/O，网络通信以及采用新的编程标准如IEC 61131-3。
