PLC
(1) The development from switch quantity control to sequential control and transportation processing is a bottom-up process.
(2) Continuous PID control and other functions, with PID in the interrupt station.
(3) One PC can be used as the master station and multiple PLCs of the same type can be used as slave stations.
(4) Alternatively, one PLC can be the master station and multiple PLCs of the same type can be the slave stations to form a PLC network. The advantage of this over using a PC as the master station is that when users are programming, they do not need to know the communication protocol; they only need to write the code according to the instruction manual format.
(5) The PLC grid can be used as an independent DCS/TDCS or as a subsystem of DCS/TDCS.
(6) Large systems are similar to DCS/TDCS, such as TDC3000, CENTUMCS, WDPFI, MOD300.
(7) PLC networks such as Siemens' SINEC-L1, SINEC-H1, S4, S5, S6, S7, etc., GE's GENET, and Mitsubishi's MELSEC-NET and MELSEC-NET/MINI.
(8) It is mainly used for sequential control in industrial processes. New PLCs also have closed-loop control functions.
(9) Manufacturers: GOULD (USA), AB (USA), GE (USA), OMRON (Japan), MITSUBISHI (Japan), Siemens (Germany), etc.
DCS or TDCS
(1) Distributed Control System (DCS) and Distributed Control System (TDCS) are monitoring technologies that integrate 4C (Communication, Computer, Control, CRT) technologies.
(2) A large tree-like topology system from top to bottom, in which communication is the key.
(3) In the interrupt station, the PID is connected to the computer and the field instruments and control devices.
(4) It is a tree topology and a parallel continuous link structure, and there are also a large number of cables running in parallel from the relay station to the field instruments.
(5) Analog signals, A/D-D/A, and microprocessor-based hybrid signals.
(6) One instrument is connected to the I/O with one pair of wires, and then connected to the local area network (LAN) by the control station.
(7) DCS is a three-level structure consisting of control (engineer station), operation (operator station), and field instruments (field measurement and control station).
(8) The disadvantages are high cost, non-interchangeability and non-interoperability of products from different companies, and different large DCS systems from different companies.
(9) Used for large-scale continuous process control, such as petrochemicals.
(10) Manufacturers: Bailey (USA), Westinghous (USA), HITACH (Japan), LEEDS & NORTHRMP (USA), SIEMENS (Germany), Foxboro (USA), ABB (Switzerland), Hartmann & Braun (Germany), Yokogawa (Japan), Honewell (USA), Taylor (USA), etc.
FCS
(1) The basic tasks are: inherent safety, dangerous areas, volatile processes, and difficult-to-handle extraordinary environments.
(2) Fully digital, intelligent, and multifunctional instruments, meters, and control devices replace analog single-function instruments, meters, and control devices.
(3) Use two wires to connect the scattered field instruments, control devices, PID controllers and control center, replacing the two wires for each instrument.
(4) On the bus, PID is equal to instruments, meters and control devices.
(5) Multivariable, multi-node, serial, digital communication systems replace single-variable, single-point, parallel, analog systems.
(6) It is interconnected, two-way, and open, replacing one-way and closed.
(7) Replace centralized control stations with decentralized virtual control stations.
(8) It can be operated by the on-site computer and can also be connected to the host computer and the next level computer on the same bus.
(9) Local area network, which can then be connected to the Internet.
(10) Change the traditional signal standards, communication standards and system standards into the enterprise management network.
(11) Manufacturers: Honeywell, Smar, Fisher-Rosemount, AB/Rockwell, Elsag-Bailey, Foxboro, Yamatake, Yokogawa, Siemens, GEC-Alsthom, Schneider, Proceeds-Data, ABB, etc.
(12) Typical of the three types of FCS
1) In continuous process automation control, such as in petrochemicals, intrinsically safe explosion-proof technology is absolutely crucial. Typical products include FF, WorldFIP, and Profibus-PA.
2) Separate automatic control of process actions, such as automobile manufacturing robots and automobiles, with typical products being Profibus-DP and CANbus;
3) Multi-point control, such as building automation, with typical products being LONWork and Profibus-FMS.
From the above description of the basic points, have we noticed that none of the three major systems used for process control were developed specifically for power plants? In other words, in their initial development stages, power plants were not the primary control target. Furthermore, the user manuals for these systems never explicitly mention power plants as their primary application scope; some don't even mention them at all. What's strange now is that these three major control systems, especially DCS and PLC, are widely used in power plants with excellent results.
