I. Overview With the development and application of computer control and management technology, the application of computer control systems for thermal power plants has been extensive, especially large-scale units of 300 MW or more.
From the control part, existing thermal power plants (especially 300 MW or more) are equipped with more advanced and reliable control systems. Usually, the control unit is divided according to the workshop, and the boiler and turbine part adopt the DCS control system (the electrical part has not yet entered the DCS control and is mainly based on conventional control), and some auxiliary workshops such as ash removal, chemical water treatment, condensate polishing, coal transportation These larger control units have begun to monitor the PLC+CRT station as the main control method. There are also some smaller decentralized systems, such as: circulating water, slag removal, soot blowing, and water pump rooms. The situation adopts different control schemes, some use the regular button, switch control, some use small-scale PI ~ control, but the control systems are mutually independent and dispersed.
From the management point of view, thermal power plants have not yet formed internal management and production computer networks. At present, more traditional management methods and methods are still used: Information communication between internal management parts and production parts of power plants depends on statistical reports and manual transmission, and information is lagging behind. The realization of efficient production management leads to the waste of personnel, material resources, and financial resources, which is not conducive to high-efficiency production. Some power plants use computer management MIS systems, but the scope of networking is limited to the internal management departments (finance, personnel, etc.), and the key production departments are not networked, mainly due to the difficulties in technical and engineering implementation of control system networking (DCS and PLC products Too many types, poor network support, etc.)
In general, the current level of computer management in thermal power plants is low and the efficiency is not high; the control level is relatively high, but there are loose control structures, lack of communication links, and low utilization of computer control systems.
With the development of enterprise networked management, it is necessary to implement comprehensive computer management and control of the whole plant production and management departments of thermal power plants to form a thermal power plant enterprise-level network (Intranet) and form a new thermal power plant management and control structure. In order to improve the efficiency of production management, give full play to the advantages of computer control and management, to achieve the purpose of reducing people and increasing efficiency.
The new thermal power plant management and control structure should have the following structure (Figure 1): The whole plant forms a unified network (Intranet), including management departments (factory, chief, personnel, finance, equipment, warehouses, etc.) and production departments ( Production workshops and process units, machines, furnaces, electricity, water, coal, ash, etc.)
Functionally, organic integration of management and production information is achieved, rather than simple computer networking. The process and data of the production process can be viewed in real time from the computers of important managers, and the processed production data can be obtained for decision making. The decision-making information of the management department can be transmitted to the production department at any time, reducing intermediate links and improving management efficiency. The production department can transmit the equipment maintenance, repair, and update information necessary for production to the appropriate management department (depot, equipment, etc.) through the network at any time, and can quickly resolve the problem, which not only improves efficiency, but also reduces waste and saves resources.
To realize the management and control networking of new power plants, the following issues must be resolved:
â—† To achieve the production part of the network, including the auxiliary shop control and DCS control system;
â—† Form a high-level MIS management system for production (production management);
â—† Form the management department's MIS management system;
â—† Unified network, ultimately achieving the whole plant management and control of the Intranet network of thermal power plants.
This program focuses on the comprehensive control and networking of the auxiliary plant of the new type of power plant to solve the current production control problems in the conventional power plant and provide the basic conditions for the formation of a complete plant network.
Second, the status of the auxiliary workshop control system The existing thermal power plant auxiliary workshop control system includes: ash removal, chemical water treatment, condensate polishing, coal handling and other larger control units, and some smaller, such as: Recirculating water treatment, slag removal, pump room, etc.
Various auxiliary workshops control system control forms are various, some systems use the more advanced PLC+CRT station monitoring mode, some adopt PLC+conventional monitoring mode, some smaller workshops such as pump room do not even have a control system, only configure Conventional operating panel (buttons, switches). Moreover, the control systems of the auxiliary workshops are independent of each other, independent of each other, and do not communicate with the DCS system, forming multiple control "islands."
This kind of auxiliary workshop control method has many disadvantages: from the control system configuration, the control forms are various, and the production and maintenance are complex; from the control level, the control level is not high, and the advantage of computer control is not fully utilized; from the production point of view, the workshops are not mutually exclusive. Contact, it is difficult to achieve high-efficiency production scheduling, let alone directly to the power plant senior management directly provide effective production management information; from the management of human and material resources caused by the waste.
In response to the above problems, a power plant auxiliary workshop integrated control system scheme was proposed to form a new and efficient control structure. The new program makes use of well-developed computer control technology (distributed control, field bus technology, information management, etc.) to connect the control systems of the power plant workshops into a tight whole, give full play to their control capabilities, improve the control level, and provide the power plant networking Basic conditions.
III. Assumption of the auxiliary control system for the auxiliary workshop According to the relevant degree of the processing system, the control system of the auxiliary workshop water control workshop can be treated separately according to water, coal, ash and other systems. The water treatment workshop may include make-up water, condensate water, circulating water, wastewater, sewage, chemical dosing, chemical sampling, etc.; the coal part may include the original coal conveying workshop, fuel part, etc.; the ash processing part may include pneumatic ash removal, slag removal, and the like. The monitoring system of each process system (water, coal, ash, etc.) can be realized first, and on this basis, the integrated monitoring and networking of the auxiliary plant of the power plant can be formed. The following control structure is formed:
This auxiliary shop control system solution can be divided into four layers: management layer, monitoring layer, control layer and field layer. As shown.
â—† The management team realizes the information integration of the production workshop (including DCS and auxiliary workshops) and provides the connection with the whole plant network;
â—† The monitoring layer implements auxiliary workshop monitoring separated by water, coal, and ash process systems, including process monitoring, control operations, and system maintenance.
â—† The control layer implements the process control procedures of each workshop to provide workshop auxiliary operation functions;
â—† The field layer includes on-site I/O stations and other control interface devices, which are front-end signal processing.
Each layer is connected through a communications network and becomes a complete control system. Finally, the following monitoring functions are realized: â— Automatic control of the auxiliary workshop is realized, manual operations and manual recording are reduced;
â— Realize centralized monitoring of all auxiliary workshops, including process monitoring and operation, Wangyi parameter monitoring, and alarm processing.
â— Providing management processes with real-time information and production processes, as well as comprehensive management reports, such as cost-accounting energy monitoring.
IV. Feasibility of comprehensive control system program 4.1 Application and development of PLC+CRT station monitoring system PLC control has always occupied the main position in the auxiliary workshop control of power plants. We do not rule out the possibility of using a small DCS system to complete the comprehensive control of the auxiliary workshop. However, PLC control is the preferred method of discussion.
From the computer monitoring (CRT station) in the late 1980s, it began to be used in auxiliary workshop control, completely replacing conventional monitoring methods (analog disks, conventional secondary instrument panels, etc.), and generating PLC+computer CRT station monitoring methods. This control method has been successfully applied in many projects and has become the main control method at present. This kind of control method has obvious superiority in the process control: The configuration is flexible and convenient, the monitoring function is powerful, the system structure is compact and so on.
The monitoring mode of PLC+CRT station is a typical decentralized control system, which is similar to the structure controlled by DCS: PLC controller realizes process control program, CRT station realizes process monitoring, and provides human-machine interface.
With years of application and development, the reliability of computer monitoring has greatly improved both in hardware and software. On the hardware side, both the CPU processing speed and capability, as well as memory, external storage (hard disk), etc., are rapidly developing and constantly upgrading. In short, the hardware is no longer the main contradiction, and the main contradiction is concentrated on the software. The operating platform of the CRT station monitoring system is required to be as stable and reliable as possible. The function of the monitoring configuration software is more practical and comprehensive. In addition to providing regular monitoring functions, it should also provide functions such as operation management and network support. In recent years, the operating system of WINDOWS95/NT has gradually matured and become more and more widely used. The development of industrial control configuration software has also been rapid, from the early preparation of separate C language programs to industrial control configuration software, such as InTouch7.0, IntellutionFIX7.0 , AIMAX, China-made Kingview, etc., supporting the hardware products are more and more common, easy to implement centralized control of integrated control system for auxiliary workshops; and support for network monitoring and browsing functions, providing a means to achieve process monitoring on the entire plant network.
From the above discussion, it can be seen that the development of the monitoring technology of the PLC+CRT station can meet the monitoring requirements of the integrated control system of the auxiliary workshop.
4.2 Development of on-site I/O station application In the new auxiliary workshop comprehensive control, the PLC control unit is further developed from centralized control to decentralized and distributed. The on-site L/O control station (such as remote I) should be used as much as possible. /O) Central control room instead of centralized control.
At present, PLC control is mainly focused on centralized control in domestic power plants. The CPU station and the ldo station are placed in the control room. The control signals of the on-site valves, motors, and meters are introduced into the control room through the cable; if the distributed or decentralized control mode is adopted, the on-site I/O station is placed close to the control object on the spot. Where, the control equipment signal cable is connected to the field I/O station nearby, and the field I/O station and the CPU station are connected through the communication network. The structure of the two is shown in the figure below. Using on-site I/O stations can save a lot of cable usage, reduce on-site construction, and shorten the construction period. And using on-site I/O stations can improve the maintainability of the control system.
With the increasing maturity of fieldbus technologies and standards, digital instrumentation using fieldbus technology has developed rapidly and will replace existing 4-20mA analog instruments in the future. The fieldbus instrument can improve the efficiency of field instrument investment and maintenance, and greatly reduce the amount of field cable laying (less than the existing 1/3). In the domestic petrochemical industry has begun to use. Do not focus on discussion in this program.
4.3 Development and Application of Network Technology In recent years, manufacturers' networking has become more and more important to form a whole plant network. The application of network technology in thermal power plants has also begun to be applied in the industrial control field with the development of a mature network of various commercial applications. , such as Ethernet (Ethemet). Ethernet networking is convenient and flexible; network product types are complete and applications are reliable (supporting many manufacturers, such as HP, IBM, Cisco, 3Com, etc.); Ethernet communication speed is high, from early IOMbps to the present 100Mbps even Gigabit Ethernet; communication media supports twisted pair, coaxial cable and fiber optic cable. Many application examples have also appeared in the industrial process control field.
This type of network is more suitable for networking requirements for integrated control of auxiliary plants in thermal power plants: a flexible network structure can support the gradual expansion of the system; faster speeds can meet the monitoring requirements.
4.4 Support for hardware and software products There are many manufacturers of PLC products. Products that are widely used in the power industry, such as MODICON, SIEMENS, A-B, OMRON, etc., can meet the control requirements of the auxiliary workshop. With the increase of network applications, all hardware manufacturers have launched support products for open standard networks, such as Ethernet; some manufacturers have even launched self-contained plant-wide network solutions, such as SIEMENSHl network, A - B's ControlNet, etc. A variety of hardware products provide a variety of choices for comprehensive control of auxiliary workshops, and also provide feasibility for the gradual transformation of auxiliary workshop control systems.
The support of hardware products to the network has led to the development of software products. Each hardware vendor (PLC or DCS system) adds network hardware driver functions and support for network protocols (such as TCP/IP).
The hardware and software products provide technical support for the integrated control of power plant auxiliary workshops.
The development of the above technologies has made it possible to implement the auxiliary workshop integrated control system and even the entire plant network.
V. Auxiliary Workshop Integrated Control System Scheme 5.1 Water, Coal, and Ash System Configuration Monitoring Plan In accordance with the design of the auxiliary workshop control system, the following comprehensive control system plan is proposed for discussion. In the scheme, the monitoring form adopts "PLC control + CRT station monitoring", and the PLC control part adopts CPU station and on-site I/O method.
The program will be a large number of scattered auxiliary workshop according to the initial preparation of three kinds of process systems, part of the process monitoring to achieve the final realization of auxiliary workshop monitoring network.
The scheme structure is as shown in Figure 3:
The program control structure is divided into four layers:
On-site I/O layer: This part consists of on-site I/O stations and plant-level local control interface devices (solenoid valve box, meter box, etc.). Placed near the local equipment in each auxiliary workshop. The equipment of the on-site I/O layer differs depending on the characteristics of the control equipment of the water, coal, and ash systems. Usually, in addition to the PLCI/0 substation, there are local control device interfaces and protection boxes with higher protection levels.
Control layer: This part consists of PLC CPU station and control cabinet. The PLC CPU station has two configuration methods: (1) Configure a set of CPU units in each larger auxiliary workshop within the water, coal, and ash system; (2) Configure a set of process systems for the same process system (water, coal, and ash) . The two types of concave U stations have their own advantages and disadvantages. The configuration of a set of CPU stations can greatly reduce the cost of the control system, but the auxiliary workshops are handled by the on-site I/O station, which causes the distribution of the on-site I/O stations to be more dispersed and the distance is longer, which may cause difficulties in implementation. In the specific implementation, the CPU configuration scheme may be selected according to the actual situation. The CPU station can use hot standby, even power hot standby.
Monitoring layer: This layer is used to realize real-time monitoring of the process system. Usually configure 2-3 CRT operation/monitoring stations. It is divided into an engineer station and an operator station in terms of function, and it is also possible to combine an operator station and an engineer station, and not only an engineer station. CRT monitoring stations usually include industrial computers, large-screen high-resolution displays, mice, keyboards, and the like.
â—† The operator station is used for the operator to realize the monitoring operation of each auxiliary workshop. The operator station can realize the operation and monitoring of each auxiliary workshop. In the actual operation, a relatively fixed operation station can be set up according to the division of the auxiliary workshop.
â—† Engineer Station is used to program, download, upload, and monitor the control logic of each auxiliary workshop, monitor system configuration and routine maintenance management.
Management: This layer is the highest level of auxiliary workshop monitoring. It mainly implements management, supervision and production scheduling functions. Only the auxiliary shop connection is listed in the above figure. From the perspective of the whole plant, DCS can be integrated into this layer as a whole plant production management. Coordinate the operations between the auxiliary workshops and the control room DCS, and manage daily transactions, such as work ticket management.
The four control layers are connected together via a communication network and there are three communication networks:
(1) Communication network between the field I/O station and the control layer CPU station: This part of the network mainly depends on the selection of the PLC, and varies with the PLC manufacturers. If the PLC is MODICON Quantum, the network may be RIO or MB+; for SIEMENS S7, the network may be SINECL2 or H1. This part of the network can use redundant configurations or ring structures. The part of the communication medium is usually shielded twisted pair or coaxial cable;
(2) Communication network between control layer and monitoring layer: There may be two kinds of network modes. One is the use of PLC communication network to achieve communication with the host station; the other uses a unified network form such as Ethernet or RS485 network to achieve communication with the host station; the first network mode usually can guarantee between the monitoring layer and the control layer Real-time requirements, but when the types of CPU stations vary greatly, the networking is complicated; the second way can support multiple types of CPU stations, but the real-time nature needs to be examined (if the number of CPU stations is small, you can also Meet real-time requirements).
(3) The communication network between the monitoring layer and the management: This part of the network mainly supports the communication between computers. Usually, more popular computer networks such as Ethemet can be used. Due to many support products, higher network speeds such as 100M or higher may be selected. Communication media can also choose UTP, optical fiber and so on.
In summary, the program has the following main features:
(1) According to the water, coal, and ash systems, the auxiliary workshops will be decomposed and concentrated, and the auxiliary workshops will be gradually networked, which has better implementability;
(2) The monitoring layer adopts a PLC control network, which can better guarantee the real-time monitoring; the management adopts a flexible computer network to facilitate network interconnection and system expansion;
(3) Auxiliary workshops collaborate to configure control systems based on water, coal, and ash process system groups, which can provide significant savings in control resources, as well as ease of production maintenance and operation management.
Some points to note about the implementation of this program:
(1) PLC selection: Due to the PLC manufacturers, the selection should be optimized. The selection module supports a wide range of devices that support on-site I/O, CPU hot standby, and network redundancy, such as MODICON, SIEMENS, and A-B.
(2) On-site I/O station: The on-site L/O unit has been mature for many years from a technical point of view and needs to be strengthened. Should fully consider the situation on the scene, configure the equipment with higher protection level (IP56 or NEMA4). In the water treatment workshop, the waterproof of the on-site I/O control box should be guaranteed; the dust-removal workshop should be protected against dust.
(3) Engineering configuration: firstly, we must select a configuration software with strong functions to support more hardware products, such as InTouchFix; secondly, we should design a more uniform screen format based on the actual situation of the auxiliary workshop, so that the human-machine The interaction is more convenient and flexible. (As shown below)
5.2 Auxiliary Workshop Completely Centralized Monitoring Plan This plan adopts centralized control of the whole factory auxiliary workshop. The structure diagram is as follows:
The control structure can also be divided into four layers. The illustration does not include management.
The monitoring layer adopts the centralized monitoring method of the whole factory auxiliary workshop, including the operator station, the engineer station and the dispatcher station, and divides the work to complete different monitoring tasks. Auxiliary workshop centralized control room can be set up to place monitoring equipment, and can also be shared with DCS in the main control room.
The control layer and field I/O layer are the same as the 5.1 scheme.
The focus of this solution is on monitoring-level networks. Considering that there may be a variety of PLC products, Ethernet star topology is adopted. Each computer of the monitoring layer and the auxiliary shop control station (CPU) are connected together via a network hub HUB to form a network. The star structure has the following features:
â—† The network structure is flexible, easy for network expansion and maintenance, and is suitable for auxiliary workshop control applications.
â—† Each communication point in the star network structure is an independent channel. Failure of a certain communication line will not affect the normal operation of other communication nodes, and it is also convenient to check the on-site faults.
Communication network media can be selected according to the actual situation: twisted pair (UTP), coaxial cable, optical fiber. In the thermal plant auxiliary shop control system, we recommend the use of optical fiber. The optical fiber has a long communication distance and is very resistant to electromagnetic interference (EMl).
In summary, the auxiliary workshop integrated control system scheme of this structure has the following characteristics:
â— Auxiliary workshops are monitored centrally, and the configuration of each workshop process is configured uniformly. The monitoring section is both centralized and flexible, facilitating the coordination and management of the production process.
â— The monitoring level network adopts a star structure to facilitate system maintenance and expansion. Suitable for step-by-step networking in auxiliary workshops.
â— The plant-level control layer is designed to control the human-machine interface devices at the CPU station and on-site, and provide monitoring interfaces for on-site inspection personnel; as a backup monitoring method when the network of the monitoring layer is faulty.
When implementing this type of auxiliary shop control system solution, the following issues need to be noted:
â— The scheme is easy to implement step by step, and the networking process can be gradually realized according to the actual situation of the power plant auxiliary workshop;
â— Ethemet network is used as the monitoring level network. The number of nodes must be controlled to ensure the real-time performance of the network.
â— Considering the selection of hub HUB, the reliability and performance of the device are critical to the operation of the network.
â— When designing the system network layout, the wiring requirements of each workshop communication network should be considered;
5.3 Remodeling Scheme The structure of this program is shown in the figure below.
This scheme is more suitable for the transformation of the auxiliary workshop control system of the power plant (the workshop level monitoring method can be firstly modified, and the production part networked). Under the control method of retaining the auxiliary workshop of the existing power plant, the auxiliary workshops are networked.
In this program, centralized management and decentralized monitoring are adopted. The management team only sets the dispatcher station and engineer station; the control level still retains the workshop monitoring mode monitored by the PLC+CRT station. The network part can use either a star topology or a bus architecture.
VI. Selection of integrated control system scheme The following focuses on several major aspects of the integrated control system in the auxiliary workshop and discusses its selection and configuration.
6.1 PLC controller PLC controller optimization selection should fully consider the control capabilities and networking capabilities in two aspects. The control capability is mainly reflected in the CPU, module support and software functions. The networking capabilities are mainly reflected in the support of on-site I/O stations and advanced networks such as Ethernet. The PLC products that are currently widely used in power plants include MODICON984, Quantum m, SIEMENSS5 and S7 series, A-BPLC5 series, OMRONC200-C2000H, GEFanuc 90-30/70.
The following is a list of the main features of these products.
From the above function table, it can be seen that the major PLC product manufacturers provide more comprehensive control functions and network support functions. The control performance can be said to have different advantages. There are differences in product prices and ease of use.
6.2 Network selection Auxiliary workshop monitoring system In addition to the control network determined by PLC selection, the networking between high-level management networks or multiple PLCs is recommended to use Ethenet network, star topology, TCP/IP protocol, and network backbone media. It is recommended to use optical fiber (twisted pair can be used in the control room) and the communication rate is 10M (10/100M self-adaptive). Hub HUB and various network interface devices should use the products of famous network manufacturers. This type of selection considers the following:
â—† The Ethemet network has been developing for many years and is more reliable; it is easy to network and supports many products.
â—† Most PLC and DC5 manufacturers offer products that support the Ethenet network and the TCP/IP protocol; shielded twisted pair, coaxial cable, or fiber optic interfaces are generally provided; typically, 10 Mbit/s communication rates are supported.
â—† The use of optical fiber as a network trunk can ensure a long communication distance and reliable communication, and can meet the requirements for long-distance communication networking of auxiliary plants in power plants.
â—† The well-known industrial control configuration software also provides support for the Ethemet network, which can reduce software development caused by networking.
Management-level networks can use fast Ethemet network (100M or 1000M). The network communication protocol selects TCP/Ip and the operating system selects WINDWOSNT or WINDOWS95(98).
6.3 Monitoring Level Hardware and Software Selection Monitor level hardware is configured as usual with IPC, large-screen color display, keyboard and mouse, and voice alarm system (sound card, anti-magnetic speaker, etc.) can also be configured as required.
The general configuration is as follows:
Host computer Pentium 233MHz, 32M, 3.2G (or higher)
Color Display 21"1024*768*256 Color (or higher)
The software includes three parts: operating system, monitoring configuration software and application software. The operating system can recommend WIN95/98 or WINDWOSNT. The monitoring software selects the more popular configuration software packages: FIX7.0, LnTouch7.0, AIMAX, etc. Application software is implemented by the engineering company that implements the project.
From the control part, existing thermal power plants (especially 300 MW or more) are equipped with more advanced and reliable control systems. Usually, the control unit is divided according to the workshop, and the boiler and turbine part adopt the DCS control system (the electrical part has not yet entered the DCS control and is mainly based on conventional control), and some auxiliary workshops such as ash removal, chemical water treatment, condensate polishing, coal transportation These larger control units have begun to monitor the PLC+CRT station as the main control method. There are also some smaller decentralized systems, such as: circulating water, slag removal, soot blowing, and water pump rooms. The situation adopts different control schemes, some use the regular button, switch control, some use small-scale PI ~ control, but the control systems are mutually independent and dispersed.
From the management point of view, thermal power plants have not yet formed internal management and production computer networks. At present, more traditional management methods and methods are still used: Information communication between internal management parts and production parts of power plants depends on statistical reports and manual transmission, and information is lagging behind. The realization of efficient production management leads to the waste of personnel, material resources, and financial resources, which is not conducive to high-efficiency production. Some power plants use computer management MIS systems, but the scope of networking is limited to the internal management departments (finance, personnel, etc.), and the key production departments are not networked, mainly due to the difficulties in technical and engineering implementation of control system networking (DCS and PLC products Too many types, poor network support, etc.)
In general, the current level of computer management in thermal power plants is low and the efficiency is not high; the control level is relatively high, but there are loose control structures, lack of communication links, and low utilization of computer control systems.
With the development of enterprise networked management, it is necessary to implement comprehensive computer management and control of the whole plant production and management departments of thermal power plants to form a thermal power plant enterprise-level network (Intranet) and form a new thermal power plant management and control structure. In order to improve the efficiency of production management, give full play to the advantages of computer control and management, to achieve the purpose of reducing people and increasing efficiency.
The new thermal power plant management and control structure should have the following structure (Figure 1): The whole plant forms a unified network (Intranet), including management departments (factory, chief, personnel, finance, equipment, warehouses, etc.) and production departments ( Production workshops and process units, machines, furnaces, electricity, water, coal, ash, etc.)
Functionally, organic integration of management and production information is achieved, rather than simple computer networking. The process and data of the production process can be viewed in real time from the computers of important managers, and the processed production data can be obtained for decision making. The decision-making information of the management department can be transmitted to the production department at any time, reducing intermediate links and improving management efficiency. The production department can transmit the equipment maintenance, repair, and update information necessary for production to the appropriate management department (depot, equipment, etc.) through the network at any time, and can quickly resolve the problem, which not only improves efficiency, but also reduces waste and saves resources.
To realize the management and control networking of new power plants, the following issues must be resolved:
â—† To achieve the production part of the network, including the auxiliary shop control and DCS control system;
â—† Form a high-level MIS management system for production (production management);
â—† Form the management department's MIS management system;
â—† Unified network, ultimately achieving the whole plant management and control of the Intranet network of thermal power plants.
This program focuses on the comprehensive control and networking of the auxiliary plant of the new type of power plant to solve the current production control problems in the conventional power plant and provide the basic conditions for the formation of a complete plant network.
Second, the status of the auxiliary workshop control system The existing thermal power plant auxiliary workshop control system includes: ash removal, chemical water treatment, condensate polishing, coal handling and other larger control units, and some smaller, such as: Recirculating water treatment, slag removal, pump room, etc.
Various auxiliary workshops control system control forms are various, some systems use the more advanced PLC+CRT station monitoring mode, some adopt PLC+conventional monitoring mode, some smaller workshops such as pump room do not even have a control system, only configure Conventional operating panel (buttons, switches). Moreover, the control systems of the auxiliary workshops are independent of each other, independent of each other, and do not communicate with the DCS system, forming multiple control "islands."
This kind of auxiliary workshop control method has many disadvantages: from the control system configuration, the control forms are various, and the production and maintenance are complex; from the control level, the control level is not high, and the advantage of computer control is not fully utilized; from the production point of view, the workshops are not mutually exclusive. Contact, it is difficult to achieve high-efficiency production scheduling, let alone directly to the power plant senior management directly provide effective production management information; from the management of human and material resources caused by the waste.
In response to the above problems, a power plant auxiliary workshop integrated control system scheme was proposed to form a new and efficient control structure. The new program makes use of well-developed computer control technology (distributed control, field bus technology, information management, etc.) to connect the control systems of the power plant workshops into a tight whole, give full play to their control capabilities, improve the control level, and provide the power plant networking Basic conditions.
III. Assumption of the auxiliary control system for the auxiliary workshop According to the relevant degree of the processing system, the control system of the auxiliary workshop water control workshop can be treated separately according to water, coal, ash and other systems. The water treatment workshop may include make-up water, condensate water, circulating water, wastewater, sewage, chemical dosing, chemical sampling, etc.; the coal part may include the original coal conveying workshop, fuel part, etc.; the ash processing part may include pneumatic ash removal, slag removal, and the like. The monitoring system of each process system (water, coal, ash, etc.) can be realized first, and on this basis, the integrated monitoring and networking of the auxiliary plant of the power plant can be formed. The following control structure is formed:
This auxiliary shop control system solution can be divided into four layers: management layer, monitoring layer, control layer and field layer. As shown.
â—† The management team realizes the information integration of the production workshop (including DCS and auxiliary workshops) and provides the connection with the whole plant network;
â—† The monitoring layer implements auxiliary workshop monitoring separated by water, coal, and ash process systems, including process monitoring, control operations, and system maintenance.
â—† The control layer implements the process control procedures of each workshop to provide workshop auxiliary operation functions;
â—† The field layer includes on-site I/O stations and other control interface devices, which are front-end signal processing.
Each layer is connected through a communications network and becomes a complete control system. Finally, the following monitoring functions are realized: â— Automatic control of the auxiliary workshop is realized, manual operations and manual recording are reduced;
â— Realize centralized monitoring of all auxiliary workshops, including process monitoring and operation, Wangyi parameter monitoring, and alarm processing.
â— Providing management processes with real-time information and production processes, as well as comprehensive management reports, such as cost-accounting energy monitoring.
IV. Feasibility of comprehensive control system program 4.1 Application and development of PLC+CRT station monitoring system PLC control has always occupied the main position in the auxiliary workshop control of power plants. We do not rule out the possibility of using a small DCS system to complete the comprehensive control of the auxiliary workshop. However, PLC control is the preferred method of discussion.
From the computer monitoring (CRT station) in the late 1980s, it began to be used in auxiliary workshop control, completely replacing conventional monitoring methods (analog disks, conventional secondary instrument panels, etc.), and generating PLC+computer CRT station monitoring methods. This control method has been successfully applied in many projects and has become the main control method at present. This kind of control method has obvious superiority in the process control: The configuration is flexible and convenient, the monitoring function is powerful, the system structure is compact and so on.
The monitoring mode of PLC+CRT station is a typical decentralized control system, which is similar to the structure controlled by DCS: PLC controller realizes process control program, CRT station realizes process monitoring, and provides human-machine interface.
With years of application and development, the reliability of computer monitoring has greatly improved both in hardware and software. On the hardware side, both the CPU processing speed and capability, as well as memory, external storage (hard disk), etc., are rapidly developing and constantly upgrading. In short, the hardware is no longer the main contradiction, and the main contradiction is concentrated on the software. The operating platform of the CRT station monitoring system is required to be as stable and reliable as possible. The function of the monitoring configuration software is more practical and comprehensive. In addition to providing regular monitoring functions, it should also provide functions such as operation management and network support. In recent years, the operating system of WINDOWS95/NT has gradually matured and become more and more widely used. The development of industrial control configuration software has also been rapid, from the early preparation of separate C language programs to industrial control configuration software, such as InTouch7.0, IntellutionFIX7.0 , AIMAX, China-made Kingview, etc., supporting the hardware products are more and more common, easy to implement centralized control of integrated control system for auxiliary workshops; and support for network monitoring and browsing functions, providing a means to achieve process monitoring on the entire plant network.
From the above discussion, it can be seen that the development of the monitoring technology of the PLC+CRT station can meet the monitoring requirements of the integrated control system of the auxiliary workshop.
4.2 Development of on-site I/O station application In the new auxiliary workshop comprehensive control, the PLC control unit is further developed from centralized control to decentralized and distributed. The on-site L/O control station (such as remote I) should be used as much as possible. /O) Central control room instead of centralized control.
At present, PLC control is mainly focused on centralized control in domestic power plants. The CPU station and the ldo station are placed in the control room. The control signals of the on-site valves, motors, and meters are introduced into the control room through the cable; if the distributed or decentralized control mode is adopted, the on-site I/O station is placed close to the control object on the spot. Where, the control equipment signal cable is connected to the field I/O station nearby, and the field I/O station and the CPU station are connected through the communication network. The structure of the two is shown in the figure below. Using on-site I/O stations can save a lot of cable usage, reduce on-site construction, and shorten the construction period. And using on-site I/O stations can improve the maintainability of the control system.
With the increasing maturity of fieldbus technologies and standards, digital instrumentation using fieldbus technology has developed rapidly and will replace existing 4-20mA analog instruments in the future. The fieldbus instrument can improve the efficiency of field instrument investment and maintenance, and greatly reduce the amount of field cable laying (less than the existing 1/3). In the domestic petrochemical industry has begun to use. Do not focus on discussion in this program.
4.3 Development and Application of Network Technology In recent years, manufacturers' networking has become more and more important to form a whole plant network. The application of network technology in thermal power plants has also begun to be applied in the industrial control field with the development of a mature network of various commercial applications. , such as Ethernet (Ethemet). Ethernet networking is convenient and flexible; network product types are complete and applications are reliable (supporting many manufacturers, such as HP, IBM, Cisco, 3Com, etc.); Ethernet communication speed is high, from early IOMbps to the present 100Mbps even Gigabit Ethernet; communication media supports twisted pair, coaxial cable and fiber optic cable. Many application examples have also appeared in the industrial process control field.
This type of network is more suitable for networking requirements for integrated control of auxiliary plants in thermal power plants: a flexible network structure can support the gradual expansion of the system; faster speeds can meet the monitoring requirements.
4.4 Support for hardware and software products There are many manufacturers of PLC products. Products that are widely used in the power industry, such as MODICON, SIEMENS, A-B, OMRON, etc., can meet the control requirements of the auxiliary workshop. With the increase of network applications, all hardware manufacturers have launched support products for open standard networks, such as Ethernet; some manufacturers have even launched self-contained plant-wide network solutions, such as SIEMENSHl network, A - B's ControlNet, etc. A variety of hardware products provide a variety of choices for comprehensive control of auxiliary workshops, and also provide feasibility for the gradual transformation of auxiliary workshop control systems.
The support of hardware products to the network has led to the development of software products. Each hardware vendor (PLC or DCS system) adds network hardware driver functions and support for network protocols (such as TCP/IP).
The hardware and software products provide technical support for the integrated control of power plant auxiliary workshops.
The development of the above technologies has made it possible to implement the auxiliary workshop integrated control system and even the entire plant network.
V. Auxiliary Workshop Integrated Control System Scheme 5.1 Water, Coal, and Ash System Configuration Monitoring Plan In accordance with the design of the auxiliary workshop control system, the following comprehensive control system plan is proposed for discussion. In the scheme, the monitoring form adopts "PLC control + CRT station monitoring", and the PLC control part adopts CPU station and on-site I/O method.
The program will be a large number of scattered auxiliary workshop according to the initial preparation of three kinds of process systems, part of the process monitoring to achieve the final realization of auxiliary workshop monitoring network.
The scheme structure is as shown in Figure 3:
The program control structure is divided into four layers:
On-site I/O layer: This part consists of on-site I/O stations and plant-level local control interface devices (solenoid valve box, meter box, etc.). Placed near the local equipment in each auxiliary workshop. The equipment of the on-site I/O layer differs depending on the characteristics of the control equipment of the water, coal, and ash systems. Usually, in addition to the PLCI/0 substation, there are local control device interfaces and protection boxes with higher protection levels.
Control layer: This part consists of PLC CPU station and control cabinet. The PLC CPU station has two configuration methods: (1) Configure a set of CPU units in each larger auxiliary workshop within the water, coal, and ash system; (2) Configure a set of process systems for the same process system (water, coal, and ash) . The two types of concave U stations have their own advantages and disadvantages. The configuration of a set of CPU stations can greatly reduce the cost of the control system, but the auxiliary workshops are handled by the on-site I/O station, which causes the distribution of the on-site I/O stations to be more dispersed and the distance is longer, which may cause difficulties in implementation. In the specific implementation, the CPU configuration scheme may be selected according to the actual situation. The CPU station can use hot standby, even power hot standby.
Monitoring layer: This layer is used to realize real-time monitoring of the process system. Usually configure 2-3 CRT operation/monitoring stations. It is divided into an engineer station and an operator station in terms of function, and it is also possible to combine an operator station and an engineer station, and not only an engineer station. CRT monitoring stations usually include industrial computers, large-screen high-resolution displays, mice, keyboards, and the like.
â—† The operator station is used for the operator to realize the monitoring operation of each auxiliary workshop. The operator station can realize the operation and monitoring of each auxiliary workshop. In the actual operation, a relatively fixed operation station can be set up according to the division of the auxiliary workshop.
â—† Engineer Station is used to program, download, upload, and monitor the control logic of each auxiliary workshop, monitor system configuration and routine maintenance management.
Management: This layer is the highest level of auxiliary workshop monitoring. It mainly implements management, supervision and production scheduling functions. Only the auxiliary shop connection is listed in the above figure. From the perspective of the whole plant, DCS can be integrated into this layer as a whole plant production management. Coordinate the operations between the auxiliary workshops and the control room DCS, and manage daily transactions, such as work ticket management.
The four control layers are connected together via a communication network and there are three communication networks:
(1) Communication network between the field I/O station and the control layer CPU station: This part of the network mainly depends on the selection of the PLC, and varies with the PLC manufacturers. If the PLC is MODICON Quantum, the network may be RIO or MB+; for SIEMENS S7, the network may be SINECL2 or H1. This part of the network can use redundant configurations or ring structures. The part of the communication medium is usually shielded twisted pair or coaxial cable;
(2) Communication network between control layer and monitoring layer: There may be two kinds of network modes. One is the use of PLC communication network to achieve communication with the host station; the other uses a unified network form such as Ethernet or RS485 network to achieve communication with the host station; the first network mode usually can guarantee between the monitoring layer and the control layer Real-time requirements, but when the types of CPU stations vary greatly, the networking is complicated; the second way can support multiple types of CPU stations, but the real-time nature needs to be examined (if the number of CPU stations is small, you can also Meet real-time requirements).
(3) The communication network between the monitoring layer and the management: This part of the network mainly supports the communication between computers. Usually, more popular computer networks such as Ethemet can be used. Due to many support products, higher network speeds such as 100M or higher may be selected. Communication media can also choose UTP, optical fiber and so on.
In summary, the program has the following main features:
(1) According to the water, coal, and ash systems, the auxiliary workshops will be decomposed and concentrated, and the auxiliary workshops will be gradually networked, which has better implementability;
(2) The monitoring layer adopts a PLC control network, which can better guarantee the real-time monitoring; the management adopts a flexible computer network to facilitate network interconnection and system expansion;
(3) Auxiliary workshops collaborate to configure control systems based on water, coal, and ash process system groups, which can provide significant savings in control resources, as well as ease of production maintenance and operation management.
Some points to note about the implementation of this program:
(1) PLC selection: Due to the PLC manufacturers, the selection should be optimized. The selection module supports a wide range of devices that support on-site I/O, CPU hot standby, and network redundancy, such as MODICON, SIEMENS, and A-B.
(2) On-site I/O station: The on-site L/O unit has been mature for many years from a technical point of view and needs to be strengthened. Should fully consider the situation on the scene, configure the equipment with higher protection level (IP56 or NEMA4). In the water treatment workshop, the waterproof of the on-site I/O control box should be guaranteed; the dust-removal workshop should be protected against dust.
(3) Engineering configuration: firstly, we must select a configuration software with strong functions to support more hardware products, such as InTouchFix; secondly, we should design a more uniform screen format based on the actual situation of the auxiliary workshop, so that the human-machine The interaction is more convenient and flexible. (As shown below)
5.2 Auxiliary Workshop Completely Centralized Monitoring Plan This plan adopts centralized control of the whole factory auxiliary workshop. The structure diagram is as follows:
The control structure can also be divided into four layers. The illustration does not include management.
The monitoring layer adopts the centralized monitoring method of the whole factory auxiliary workshop, including the operator station, the engineer station and the dispatcher station, and divides the work to complete different monitoring tasks. Auxiliary workshop centralized control room can be set up to place monitoring equipment, and can also be shared with DCS in the main control room.
The control layer and field I/O layer are the same as the 5.1 scheme.
The focus of this solution is on monitoring-level networks. Considering that there may be a variety of PLC products, Ethernet star topology is adopted. Each computer of the monitoring layer and the auxiliary shop control station (CPU) are connected together via a network hub HUB to form a network. The star structure has the following features:
â—† The network structure is flexible, easy for network expansion and maintenance, and is suitable for auxiliary workshop control applications.
â—† Each communication point in the star network structure is an independent channel. Failure of a certain communication line will not affect the normal operation of other communication nodes, and it is also convenient to check the on-site faults.
Communication network media can be selected according to the actual situation: twisted pair (UTP), coaxial cable, optical fiber. In the thermal plant auxiliary shop control system, we recommend the use of optical fiber. The optical fiber has a long communication distance and is very resistant to electromagnetic interference (EMl).
In summary, the auxiliary workshop integrated control system scheme of this structure has the following characteristics:
â— Auxiliary workshops are monitored centrally, and the configuration of each workshop process is configured uniformly. The monitoring section is both centralized and flexible, facilitating the coordination and management of the production process.
â— The monitoring level network adopts a star structure to facilitate system maintenance and expansion. Suitable for step-by-step networking in auxiliary workshops.
â— The plant-level control layer is designed to control the human-machine interface devices at the CPU station and on-site, and provide monitoring interfaces for on-site inspection personnel; as a backup monitoring method when the network of the monitoring layer is faulty.
When implementing this type of auxiliary shop control system solution, the following issues need to be noted:
â— The scheme is easy to implement step by step, and the networking process can be gradually realized according to the actual situation of the power plant auxiliary workshop;
â— Ethemet network is used as the monitoring level network. The number of nodes must be controlled to ensure the real-time performance of the network.
â— Considering the selection of hub HUB, the reliability and performance of the device are critical to the operation of the network.
â— When designing the system network layout, the wiring requirements of each workshop communication network should be considered;
5.3 Remodeling Scheme The structure of this program is shown in the figure below.
This scheme is more suitable for the transformation of the auxiliary workshop control system of the power plant (the workshop level monitoring method can be firstly modified, and the production part networked). Under the control method of retaining the auxiliary workshop of the existing power plant, the auxiliary workshops are networked.
In this program, centralized management and decentralized monitoring are adopted. The management team only sets the dispatcher station and engineer station; the control level still retains the workshop monitoring mode monitored by the PLC+CRT station. The network part can use either a star topology or a bus architecture.
VI. Selection of integrated control system scheme The following focuses on several major aspects of the integrated control system in the auxiliary workshop and discusses its selection and configuration.
6.1 PLC controller PLC controller optimization selection should fully consider the control capabilities and networking capabilities in two aspects. The control capability is mainly reflected in the CPU, module support and software functions. The networking capabilities are mainly reflected in the support of on-site I/O stations and advanced networks such as Ethernet. The PLC products that are currently widely used in power plants include MODICON984, Quantum m, SIEMENSS5 and S7 series, A-BPLC5 series, OMRONC200-C2000H, GEFanuc 90-30/70.
The following is a list of the main features of these products.
From the above function table, it can be seen that the major PLC product manufacturers provide more comprehensive control functions and network support functions. The control performance can be said to have different advantages. There are differences in product prices and ease of use.
6.2 Network selection Auxiliary workshop monitoring system In addition to the control network determined by PLC selection, the networking between high-level management networks or multiple PLCs is recommended to use Ethenet network, star topology, TCP/IP protocol, and network backbone media. It is recommended to use optical fiber (twisted pair can be used in the control room) and the communication rate is 10M (10/100M self-adaptive). Hub HUB and various network interface devices should use the products of famous network manufacturers. This type of selection considers the following:
â—† The Ethemet network has been developing for many years and is more reliable; it is easy to network and supports many products.
â—† Most PLC and DC5 manufacturers offer products that support the Ethenet network and the TCP/IP protocol; shielded twisted pair, coaxial cable, or fiber optic interfaces are generally provided; typically, 10 Mbit/s communication rates are supported.
â—† The use of optical fiber as a network trunk can ensure a long communication distance and reliable communication, and can meet the requirements for long-distance communication networking of auxiliary plants in power plants.
â—† The well-known industrial control configuration software also provides support for the Ethemet network, which can reduce software development caused by networking.
Management-level networks can use fast Ethemet network (100M or 1000M). The network communication protocol selects TCP/Ip and the operating system selects WINDWOSNT or WINDOWS95(98).
6.3 Monitoring Level Hardware and Software Selection Monitor level hardware is configured as usual with IPC, large-screen color display, keyboard and mouse, and voice alarm system (sound card, anti-magnetic speaker, etc.) can also be configured as required.
The general configuration is as follows:
Host computer Pentium 233MHz, 32M, 3.2G (or higher)
Color Display 21"1024*768*256 Color (or higher)
The software includes three parts: operating system, monitoring configuration software and application software. The operating system can recommend WIN95/98 or WINDWOSNT. The monitoring software selects the more popular configuration software packages: FIX7.0, LnTouch7.0, AIMAX, etc. Application software is implemented by the engineering company that implements the project.
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