Currently, the fifth-generation control system in power applications can be considered very advanced, and the standout among fifth-generation systems is the FCS control system, which evolved from PLC or DCS. Although FCS has countless connections with PLC and DCS, it also has essential differences. This article provides a brief analysis of these three.
PLC stands for Programmable Controller. PLCs can range from small "brick" devices with thousands of I/O points integrated with a processor, to large rack-mounted modular devices with thousands of I/O counts, often networked to other PLCs and SCADA systems.They can be designed for multiple arrangements of digital and analog inputs and outputs (I/O), extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs controlling machine operations are typically stored in battery-backed or non-volatile memory.
A PLC can use a PC as the master station with multiple PLCs of the same type as slaves, or one PLC as the master with multiple PLCs of the same type as slaves, forming a PLC network. The advantage over using a PC as the master is that when programming, users do not need to know the communication protocol; they only need to write according to the manual's format.
Currently, it is mainly used for sequential control in industrial processes, and new PLCs also have closed-loop control functions.
DCS stands for Distributed Control System. Generally, a DCS system receives input signals from other devices, processes and analyzes these signals with the CPU, and based on the results, takes action. Inside, there are various sensors for physical quantities such as pressure and temperature, and transmitters that convert these into electrical signals to represent them in the DCS system.
During operation, when the PLC receives signals from different transmitters, it converts them into digital signals through input modules, then passes the analog signals to the central processor. The CPU compares the process measurement value (PV) with the setpoint (SV). If the two values do not match, the DCS will generate an output called the manipulated value (MV) through the output module to regulate the physical quantity by operating valves.
However, the disadvantages of DCS systems are high cost, products from different companies cannot be interchanged, and they cannot interoperate. Large DCS systems are different among various manufacturers.
FCS stands for Focus Control System. It is currently a very advanced fifth-generation process control system and is the development direction of automation control systems in the 21st century, integrating C technologies (Communication, Computer, Control).
FCS is fully digital, intelligent, and multifunctional, replacing analog single-function instruments, meters, and control devices. It embeds microprocessors into field automation equipment, enabling devices to have digital computation and digital communication capabilities, with high signal transmission accuracy and remote transmission. It achieves fully digital signal transmission, decentralized control functions, and standardized, fully open systems.
In summary, FCS has good openness, interoperability, and interchangeability, along with fully digital communication and intelligence.
