Application of DCS Control System in Thermal Power Station

DCS is the abbreviation of Distributed Control System (DistributedControl System), which is also called distributed control system in the domestic self-control industry. It is a new type of computer control system compared to the centralized control system. It is developed and evolved based on the centralized control system.

It is a multi-level computer system consisting of a process control level and a process monitoring level, which is a communication network. It integrates computer, communication, display and control 4C technologies. The basic idea is decentralized control, centralized operation, hierarchical management, Flexible configuration and easy configuration.

In special control areas, such as nuclear power plant control systems, the meaning of DCS is incorrectly called the digital control system (Digital control system), which is still a distributed operating system.

The Jintai Thermal Power Station is a 3xl30t/h+Zx25MW thermal power unit, and its thermal control system uses DCS as the main monitoring and control method. The DCS system was selected as the I/Ase-ires decentralized control system of Foxboro. It is a DCS system that combines Uinx and Window, NT operating systems; and uses the company's widnows Jun Yu shoots the mouth by the N7T0 series of processing machines, and its engineering station is the AW70DsC control system medicine and processing machine, and the operator station is the WP7O processor. This is a reliable logic. The first test of Shanghai-Fox Polo Co., Ltd.·WindowsNT70 series I/ASeries system is used in the production of Haichai and thermal power plants. After more than a year of operation and practice, it has achieved “dangerous dispersion, control dispersion, and centralized monitoring”, which played a significant role in production.

Overview DCS control systems include data acquisition and processing (DAS), analog control (MCS), JI sequence control (SCS), turbine accident trip (ETS), furnace safety monitoring (FSS) S, and electrical monitoring systems (EC) S six major systems. At the same time, it has the functions of communication with other suppliers' control systems and equipment (electro-hydraulic speed control system DEH, program-controlled soot-blowing PLC system, electrical integrated automation, chemical water treatment PLC control system, etc.), and is responsible for related interface work. In order to transmit the necessary information and data through the same bus, accept the unified scheduling and command of the control system to form a complete control system. In addition, ensure that the necessary hard operation control is set.

Because the protection principle of the electrical relay protection system is complex and professional, it has a very important position in the power plant, so the reliability, sensitivity, quickness and selectivity between various protections are very good. The high requirements are not suitable for DCS to realize the protection function. Therefore, the monitoring of the 110kV, 35kV power distribution device, 10kV bus, and generator is completed by the DCS system; its electrical protection is realized by the microcomputer protection device.

Main features of the system

(l) The system is a microprocessor-based intelligent decentralized structure. The close combination of software and hardware enables the system to fully play its role; and the traditional one-on-one monitoring of strong electric power becomes centralized monitoring of the computer screen.

(2) The system provides Windows Chinese operation interface, which is convenient for the operation and monitoring of the operating personnel. The configuration environment is the same as the 50 series I/ASeries running uinx operating system, and the configuration is programmed with r0RTR^N and C language, which enhances the system. reliability.

(3) The controller adopts redundant configuration to provide self-diagnosis function in the system management software to the module level, so that the system has high reliability. Failure of any component in the system will not affect the operation of the entire system.

(4) Networking of the underlying connection, full intelligence of the 1/0 module, redundant technology of hot backup, and reliable technical features of live plugging.

(5) The system network is 10M redundant fast Ethernet, which greatly accelerates the network speed and leaves sufficient room for future expansion and transformation.

(6) Configuration software function has a variety of standard configuration tools, CAD-style drawing tools and a rich graphics library, which can quickly draw a flow chart that meets user requirements.

(7) With open and flexible communication interface support, the electrical integrated automation, chemical water treatment control system, etc. will be integrated into the DCS system by standard communication RS232 and Ethernet methods, which maximizes the sharing of information and resources, and is beneficial to the microcomputer. Centralized monitoring saves investment.

System division

The entire DCS system is divided into seven functional areas according to the main object of the whole power plant. They are: 1# boiler, 2# boiler, 3# boiler, 1# steam turbine, 2# steam turbine, utility system, and electrical. Each functional area is divided into several functional groups according to the process system, which is used to complete each group of equipment control and operation. Each function group is divided into several sub-function groups for completing the control and operation of each device.

(l) Each boiler functional area is divided into five functional groups: boiler steam water function group, air supply function group, flue gas system function group, fuel system function group, and powder system function group.

(2) Each steam turbine functional area is divided into three functional groups: they are: soda water, heat recovery system function group; circulating water and extraction system function group; security oil system function group.

(3) The deaeration and decompression and decompression functional zones are divided into three functional groups: deaerator, feedwater pump functional group; desuperheating and decompression functional group; hydrophobic, backwater, industrial water functional group.

(4) The electrical monitoring function area is divided into five functional groups: generator function group, factory 10kV function group, factory 380V/220V function group, transformer function group, and boost station function group (110kV, 35kV, 10kV).

System hardware configuration and network

Three boilers, two steam turbines, electrical and utility systems use a DCS decentralized control system, consisting mainly of engineering stations, operator stations, and on-site control stations (1/0 stations), each boiler, each turbine, and utility system. And electrical control is implemented in different control stations. The control system power supply is powered by uPSAc220v and redundant power distribution is considered. The entire DCS system consists of 7 control units (concentrated in one control cabinet), 13 1/0 cabinets, 6 relay cabinets, 1 power distribution cabinet, 1 engineering station, and 8 operator stations.

1 engineer station

The engineer station is AW7001, which centrally controls and manages the whole system. It is mainly used for program development, system diagnosis, control system configuration, database and screen editing and modification of steam turbine and boiler DCS system. The configuration of the electrical DCS is on the Aw7002 (Electrical Engineering Station and Operator Station). The engineer station sets the software protection password to prevent the general personnel from changing the control strategy, the usage program and the system database. The basic configuration is as follows:

(l) Host: PENTIUMW/2. SGH: 512MB RAM, soG hard drive, 3.5-inch floppy drive, node bus interface card, 101 standard keyboard, mouse, readable and writable optical drive.

(2) Display: 21-inch CRT, 256 colors, l600x1280 pixels, dot distance detection 0. 26; refresh frequency) 85H:; with anti-glare, anti-static, low-radiation function.

(3) System software: WindowsXP operating system.

(4) 4 alarm recording printers, color laser printer 1

Operator station

There are 8 operator stations, including 3 boilers (W7P001, WA7002, WP7007), 2 steam turbines (WP7004, WP7005), 1 common WP7O03, and 2 electric (W7P06, AW7002). Its task is to collect and display relevant operational information on the standard screen and the user configuration screen, so that the operating personnel can monitor and control the operating conditions of the unit accordingly. In order to prevent the operator station from modifying the control program, the system has a protection password for entering the engineer environment. The basic configuration is as follows:

(l) Operator host: PENTIUMW/2. SGHz, 256MB memory, SOG hard disk, node bus interface card, dedicated keyboard or 101 standard keyboard, ball standard.

(2) Display: 21-inch CRT, 256 colors, l600x1280 pixels, dot pitch falling off 0. 26; refresh rate) 85H:; with anti-glare, anti-static, low-radiation function.

(3) System software: Window, XP operating system platform and operator software.

Field control station (1/0 station)

The field control station is composed of the main control unit, intelligent 1/0 unit, power supply unit, field bus and dedicated cabinet. It adopts distributed structure and has strong expandability. The main control unit runs the control program downloaded by the engineering station, performs engineering unit transformation and control calculation, and communicates with the engineering station and the operator station through the node bus to complete data exchange. The fieldbus provides a communication link for data exchange between the main control unit and the 1/0 unit.

The on-site control station is set separately for single furnace and single unit, that is, 3 boilers are divided into 3 field control stations (3 pairs of redundant controllers C6P0), which are CP6001, CP6002, CP6003 respectively; 2 steam turbines have 2 field control stations (2 For the redundant controller CP60), respectively, Cp60o4, cp6005; for the public system, one field control station is CP6006 (l pair redundant controller CP60); and one field control station is set to CP6007 (l pair redundant controller) CP60).

Communications network

The DCS system has a set of redundant communication networks, which consist of two network layers: the monitoring network and the control network. The monitoring network adopts the node bus, which is mainly used for the communication connection between the engineering station, the operator station and the field control station; the control network exists inside each field control station, and the field bus is used, mainly for the main control unit equipment and the 1/0 unit. The communication connection of the device.

Both the node bus and the fieldbus are redundantly designed, and the redundant data communication bus operates at the same time at a communication speed of 10oMhit/s. The failure of any system or device connected to the data communication system does not cause the communication system to paralyze or affect the operation of other networked systems and devices. The interface between any station and the data communication network is passive. A failure of the communication bus does not cause the unit to trip or disable the decentralized controller.

Number of on-site FO signals

The total number of 1/0 signals of 3 sets of 130t/h boilers, 2 25MW steam turbines, public systems and electrical control systems is 4256 points, including Al point 1484, AO point 176, Dl point l348, DO point 924, Pl point 76. , SOE point 238, after adding 15% margin, the actual configuration is 5120 points.

Data Acquisition System (DAS)

Continuously collect and process all important measuring points and equipment status signals related to the unit, so as to provide relevant operational information to the operators in time to achieve safe and economic operation of the unit. When any abnormal working condition occurs in the unit, an alarm will be issued in time to improve the availability of the unit. The included functions are: process data acquisition and display; process flow chart, bar graph, trend graph display; process alarm display; CRT soft light card and voice alarm; historical data recording and display; SOE record.

Analog t control system (MCS)

The MCS system automatically completes the loop regulated by the control variable through control variables. The main functions are as follows:

(1) The main steam pipe pressure automatic adjustment system is established between the boiler and the steam turbine and the heating system to maintain a constant relationship between the main pipe pressure and the main steam pipe pressure. It utilizes the change of the amount of coal powder in the parallel operation of the boiler as a means of adjustment to adapt to the heat load and the electric load, that is, the change of the gas consumption, to achieve the purpose of maintaining the pressure of the main steam main pipe.

(2) Turbine control Turbine control is mainly realized by the DEH system provided by the steam turbine plant.

(3) The boiler control consists of several subsystems, which should be operated in coordination; and with feedforward characteristics, so that the boiler can operate sensitively, safely, quickly and stably, and ensure that the unit load command requirements are met under any working condition. . Including coal mill control, secondary air volume control, bellows baffle control, primary air duct pressure control, furnace pressure control, main steam temperature control, feed water control, fuel pressure control, deaerator water level and pressure control, high and low water level control.

Sequential control system (S piece)

For the auxiliary and auxiliary systems of the thermal power unit, the automatic control system for starting or stopping the process is realized in the order specified by the operating procedures (input signal condition sequence, action sequence or time sequence). The SCS system controls all auxiliary machines, valves and baffles and control equipment of the unit to protect and interlock. The main objects controlled are: boiler steam water system, boiler combustion system, boiler air system, boiler flue gas system, boiler ignition fuel system, steam turbine. Steam system, turbine lubricating oil system and coiling vehicle, condenser vacuum, circulating water system, desuperheating and decompressing system, deaerator water supply system.

Furnace Safety Monitoring System (SFS)

The boiler ignition and oil gun are automatically controlled by the program, and the monitoring and automatic control measures are taken to prevent the furnace furnace from exploding (implosing or exploding) due to combustion, flameout, overpressure and the like. It includes the burner control system BCS and the furnace safety system FSS. The functions are: furnace purge, fuel system OFT, igniter and gun cutting control, flame monitoring and furnace fire protection, main fuel trip MFT.

Turbine Trip Protection System (EST)

Ensure that all steam inlet valves, extraction check valves, etc. of the turbine can be shut down in the following accident conditions to safely stop the turbine. Steam turbine main engine protection: low oil pressure (0. 02MaP) low vacuum (60kaP) trip, manual head stop, main control stop button stop, DEH stop, axial displacement large trip (+l.4mm), power generation Machine trip stop, electric overspeed protection, thrust bearing return oil high temperature trip (75 ° C), support bearing metal temperature high (95 ° C).

The DCS system was installed on July 5, 2005, and was commissioned on July 20, 2005. The 1# unit was first reversed for various tests on August 29, 2005. On September 2, the 1# unit was turned on again and connected to the grid. On September 24, it passed the 72h full load trial operation. The 2# unit was first turned on for various tests on January 1st, and the 2# unit was turned on again on December 13th and passed the 72h full load trial on December 16th.

Debugging step

On July 20, 2005, the system was commissioned after power-on, and the DCS system was debugged as follows:

(1) DCS system wiring and grounding inspection.

(2) DCS cabinets and cards are powered on.

(3) nCS system nl, no card inspection, RTn, rC, Al, AO card accuracy verification.

(4) Thermal protection signal, auxiliary machine, electric door status, and switching signal check.

(5) RTD, TC temperature signal, analog input, output signal check.

(6) Check and adjust the actuator opening and closing action and valve position signal.

(7) Check and adjust the opening and closing action and direction of the electric door.

(8) All test runs of boilers and steam turbines.

(9) Static interlocking and protection test of boiler and steam turbine.

Major technical issues that arise during commissioning

(l) In the static test, the opening and closing travel time of the electric door is recorded and modified to ensure that the electric door is opened and closed in time to protect the electric door in the case of jamming.

(2) The auxiliary test of the auxiliary machine is mainly to record and modify the start and stop pulse width of the auxiliary machine and determine the length of time for the auxiliary machine to operate normally. In the static test of auxiliary machinery and electric door, some auxiliary machinery and electric door interlocking conditions were discovered and modified in time to meet the actual operation requirements.

(3) In the static debugging of the actuator, it was found that the actuators such as the secondary damper and the milling system oscillate. Further inspection found that the open-loop local control actuator brakes were poor. According to the actual operation of the actuator, the dead zone of the switch was corrected one by one to ensure that the actuator did not oscillate. After modifying the deviation of the actuator valve position command and the actual valve position alarm and the deviation is greater than the allowable deviation for a certain time, the actuator valve position command will track the actual valve position.

(4) In the static test of the MCS closed-loop control system, all off-line simulation tests were carried out, the operation direction and operation accuracy of the IPD module were checked, and the large bypass control of the boiler water supply and the control scheme of the blower population baffle were adjusted.

(5) Since the water level compensation value of the steam drum of the 3# furnace Dcs is large, the deviation between the electric contact point and the local water level is large. For this reason, the configuration logic is modified, and the automatic design value of the 3# furnace feed water is set, from the original upper and lower limits (+10, -100) changed to (+100, one 200).

(6) In the DCS automatic cascade control loop, automatic tracking is not designed, and the configuration loop is modified to realize hand/automatic bumpless switching.

(7) When multiple signals are selected, a logic error is configured. For example, one of the two signals is a bad value, and should be selected after the logic is judged; if two of the three signals are good or bad, the average of the two good values ​​should be selected. However, due to a configuration error, the average value of the bad value or the bad value is selected. In addition, when the air volume signal signal is selected, a small value should be selected; and the temperature should be selected as a large value. The configuration loop has been modified.

(8) The temperature protection of lubricating oil and coal mill has caused the equipment to trip multiple times due to the instantaneous high value of the measuring point. For this reason, 105 delay is added in the original design, and the instantaneous interference signal is filtered to ensure the stable operation of the equipment.

(9) Due to design reasons, the power switch of the oil station cannot be automatically switched. It is necessary for the operating personnel to manually close the standby switch, but when the main power is lost, the oil pump has stopped and the grinding has been tripped. For this reason, in the configuration of “frequent shutdown of the grinding station” and “low oil pressure of the population”, a delay of 1805 was added, allowing the operator to resume the operation of the grinding station.

The use of DCS system in power plants has improved the level of automation control in power plant operation, greatly facilitating the daily operation of operators, and at the same time achieving the goal of energy saving, consumption reduction and efficiency increase. After the accident, it can provide a variety of effective means to carry out accident investigation and analysis, which plays a very good role in timely and accurately identifying the cause of the accident.

Reduce unplanned downtime

Through the monitoring of the key parameters affecting the operation of the unit, the operating state of the equipment is kept stable. When the operating conditions of the unit change, it can be reflected in time to avoid or reduce unnecessary losses caused by the outage of the equipment and equipment.

software programming

In software programming, because the PLC used is the PLC of the previous drafting machine, the hardware configuration work is not required; according to the already allocated 1/0 point, according to the principle of the control system, the PLC program is divided into 12 networks. Complete their respective control tasks.

The notebook computer using iSemens is connected through the DP interface of the PLC, and the communication mode is PROIFBuS communication; it can also be connected through the MIP interface of the PLC, and the communication mode is MIP communication. The pLC program of the downloading system uses the online monitoring function of the SiemensManager software to monitor the running status of the PLC program online and complete the system debugging.

Our company has two short fiber production lines. The two production lines used steam drawing and drafting heating control. Considering steam fluctuation and unstable heating, one of the production lines was transformed into a water bath draft heating control. The main product indicators that have been improved are: the elongation mean (elongation Cv). The statistical average before the transformation is å·§.67%, and the statistical average after transformation is 7.72%. The statistical average of the intensity variation (intensity Cv) before transformation is 8.12%, the statistical average after the transformation is 4.03%; at the same time, the product's heat shrinkage rate and defects (straight / parallel, C, D insect) also greatly improved. After the main technical indicators of the product were improved, the A-grade yield of the product increased by nearly 4.5 percentage points.

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