Distributed Control System (DCS), also known as distributed computer control system, is a new type of control technology that uses computer technology to centrally monitor, operate, manage and decentralize the production process. It is produced by the mutual penetration of computer technology, signal processing technology, measurement control technology, communication network technology, CRT technology, graphic display technology and human-machine interface technology. DCS is different from distributed instrument control and centralized computer control system, but overcomes the shortcomings of both and concentrates the advantages of both. The utility model has the advantages of strong versatility, flexible system configuration, perfect control function, convenient data processing, centralized display operation, friendly human-machine interface, simple and standardized installation, convenient debugging, safe and reliable operation, and can improve production automation level and management level. Reduce energy consumption and raw material consumption, increase labor productivity, ensure production safety, and create optimal economic and social benefits. DcS is the abbreviation of Distributed Control System (Down Contro System), which is commonly used in China as a distributed control system. It is a multi-level computer system composed of a process control level and a process monitoring level, which is a communication network. It integrates 4C technologies such as Computer, CommunicaTIon, Display (CRT) and Control. The basic idea is decentralized control, centralized operation, hierarchical management, and flexible configuration configuration. DCS has the following characteristics: 1 high reliability; 2 openness; 3 flexibility; 4 easy to maintain; 5 coordination; 6 control functions are complete. DCS projects in thermal power plants generally include analog control system (MCS) logic control system (SCS) boiler safety monitoring system (FSSS) unit data monitoring system (DAS) turbine monitoring and protection system (TSI) turbine electro-hydraulic control system (DEH) Wait. Analog Control System (MCS) mainly includes 1. Coordinated control system (main steam pressure control, power control, air supply control, air intake control, fuel control system) 2, water supply control system 3. Main steam temperature control system and reheat steam temperature control system 4. Machine side furnace side control system (condenser, low pressure heater, deaerator, high pressure heater) 5, milling control system 6. Turbine bypass control system (high pressure bypass, low pressure bypass) Logic Control System (SCS) : The logic control system SCS divides part of the operation of the unit into several local control systems according to the thermal system or auxiliary mechanical equipment, and operates according to the pre-specified order to achieve the purpose of sequential control. The range of furnace side sequence control includes: blower, induced draft fan, primary fan, air preheater, furnace soot blowing system, etc. The scope of the machine side sequence control system includes: turbine lubricating oil system, condensate pump, high plus, deaerator, refill, vacuum pump, shaft seal system, circulating water system, closed water system, steam pump, electric pump, internal cold water System, sealing oil system, rubber ball cleaning system, etc. 　　 Start and stop control of equipment 1, the water pump 2, blower, induced draft fan, primary fan, booster fan 3, small steam turbine 4, coal mill 5, stop valve, damper flap, etc. Boiler Safety Monitoring System (FSS) : Boiler safety monitoring FSSS can continuously monitor a large number of parameters and states of the combustion system continuously under various operating modes such as normal operation and start-stop of the boiler, continuously perform logic judgment and calculation, and issue action commands when necessary, through various sequence control. And interlocking devices, so that the relevant equipment in the combustion system (such as coal mill, coal feeder, oil gun, fire detection cooling fan, etc.) operate in strict accordance with a certain logical sequence or deal with the accidents to ensure the safety of the boiler. At the same time, the furnace safety monitoring system also has a combustion management function. It controls the firing of the various layers of the boiler to meet the needs of the unit to start and stop and increase or decrease the load. The boiler's operating parameters and status are continuously monitored and automatically completed. Various operations and protective actions, such as emergency cut-off fuel supply and emergency shutdown, to prevent accidents from expanding. 1. Boiler ignition 2, flame detection 3. Depending on fuel management 4, furnace safety protection Unit Data Monitoring System (DAS) : Data acquisition and monitoring of temperature, pressure, flow, voltage, and current Turbine Monitoring and Protection System (TSI) : vibration, rise, displacement, speed Turbine Electro-hydraulic Control System (DEH) : Turbine Regulating Control Electrical system ( ECS ) : Its main function is the start and stop control and logic of the generator; the control and logic of each switch of the plant power system; the monitoring of various parameters and equipment status of the electrical system; the relay protection action, fault alarm And chronological recording. Steam pump system ( MEH ) : Its main function is to adjust the speed of the steam pump unit, and can complete the following functions: hanging gate, speed increasing, constant speed, CCS control, overspeed protection and other functions. Bypass Control System ( BCS ) : The bypass system is a stand-alone system. The bypass control can fulfill the exact requirements of the bypass operation and can complete the safety function or the quick opening/blocking function. The basic components are divided into high. The side controller and the low side controller mainly realize the pressure control and temperature control at the high and low sides. Main technical overview of the system Desulfurization of power plants is a process to reduce the sulfur compounds in the flue gas of coal-fired units to meet the national emission standards. At present, the wet desulfurization process is widely used. The process mainly includes a process water system, a limestone slurry preparation, a conveying system, an absorption tower system, a gypsum dehydration system, a flue gas system and the like. The main equipments include wet ball mills, slurry transfer pumps, oxidation fans, slurry circulation pumps and booster fans. For its control system, the wet desulfurization process generally has the following characteristics: The control object of flue gas desulfurization is special but the quantity is small, the control object is more dispersed, the PID used for control is less, the control loop is simpler; the closed loop control is less, the open loop control is more, and the real-time requirement is not too high. In addition, there are more sequence controls, focusing on time control and less protection requirements. Therefore, the desulfurization control system is a system with a large amount of switching, supplemented by analog and accompanied by a small number of regulating loops. It is a typical hybrid control system, and its control I/O points are about 3000 points. The system adopts limestone gypsum wet desulfurization process, which is the most widely used and reliable process in the world. The process uses limestone slurry as an absorbent, and the flue gas is washed in the absorption tower through the limestone slurry to react to remove SO2 in the flue gas, and the calcium sulfite produced by the reaction is forcibly oxidized to form sulfuric acid containing two crystal water. Calcium (gypsum). With the continuous development of computer technology, communication technology and control technology, in order to meet the needs of the power grid, thermal power units must have higher adjustment and adaptability, using plant-level monitoring information system (SIS), integrated distributed control system (DCS) and The auxiliary workshop control system constitutes information sharing, and the powerful production automation network solution is advanced in technology, reasonable in plan, practical and feasible. It can further improve the economic efficiency and safety benefits of the unit, and make the operation and management level of the unit to a new level. 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Its main function is to adjust the speed of the steam turbine, and can complete the following functions: hanging brake; automatically determine the hot state; select the starting mode; speed up; 3000rpm fixed speed; generator false synchronous test; grid load; load; valve switching; Single valve / sequence valve switching; regulating stage pressure feedback; load feedback; primary frequency modulation; CCS control; ATR thermal stress control; high load limit; low load limit; valve position limit; main steam pressure limit; fast unloading load; ; meet the imbalance; overspeed protection OSP; fuel injection test; overspeed test; valve activity test; valve online setting; solenoid valve test; control mode switching. 
Thermal power plant dcs control system
What is the dcs control system?