英文文献PLC in the ice storage central air-conditioning system of control 1 Introduction In 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 90s, 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 hours of 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 systems 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 PC 2 Control system The 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