A Practical Solution for Control of Fan Drives Load in Thermal Power Plants

摘要

Many technical solutions, implemented in industry, imply dual actuators (fans, mills, pumps, valves, heaters,...). Control of these actuators is challenging, since duality provides possibility to influence the load distribution as well as regulation of specified variable. Industrial practice often defines very strict requirements related to load distribution of dual actuators. These requirements are determined by energy efficiency or process safety criteria. This paper presents an approach to pressure/under-pressure and load distribution control of fresh air supply and exhaust fans at thermal power plants, where dual actuators are used. The proposed concept, relative to standard solutions, offers better performance, simplified tuning and start-up, and safer operation in terms of over-current protection. Pressure/under-pressure and load distribution of the two fans by means of flap position relies on two PI pressure controllers, two PI current controllers (when over-current protection is active), and one PD controller for load distribution control between the two drives. The efficiency of the proposed solution is illustrated by the case of dual fan drives in thermal power plants, but the approach is general and may be applied whenever two actuators are implemented in parallel.