The Application and Prospect of Fieldbus Control System in thermal Power Plant

In the 1980s, DCS (Digital Decentralized Control System) started to enter the field of power station automation control. Because of its positive effects in terms of safety production and economic efficiency, which cannot be compared with any other control system in the past, DCS is widely used in power stations.

At present, all units above 300MW, whether domestic units or imported units, use DCS without exception, and even 200MW and 100MW units are also using DCS for transformation, and even some thermal power units of 25MW and 12MW in self-provided power plants also use DCS system.  

Then, as the most new control system in the field of automation, fieldbus control system (FCS), which only became practical in the 1990s, can it be accepted and widely used by power stations like DCS system?

1. The most significant features of FCS compared with DCS  

According to the definition of IEC1158, the digital, serial, multi-point communication data bus between the field device installed in the manufacturing or process area and the automatic control device in the control room is called fieldbus.  

A fully digital control system based on fieldbus is called fieldbus control system FCS. fieldbus is an open, fully digital, two-way communication and multi-station communication system between field instruments and control room system.   

The specific comparison of DCS and FCS is as follows.  

(1) DCS system is a large system, its controller function is strong and the role in the system is very important, the data highway is the key to the system, so the overall investment must be in place in one step, after the expansion is more difficult. While FCS function is more thoroughly decentralized, information processing field, the widespread use of digital intelligent field devices make the controller function and the importance of relatively weakened. Therefore, the FCS system investment starting point is low, and can be used, expanded and put into operation at the same time.

(2) DCS system is a closed system, the products of various companies are basically incompatible with each other. FCS system is an open system, users can choose different manufacturers, different brands of various devices connected to the fieldbus, to achieve the best system integration.

(3) The information of DCS system is all formed by binary or analog signals, which must be converted to D/A and A/D. The FCS system is fully digital, eliminating the need for D/A and A/D conversion, with high integration and high performance.