Controlling Drum Level of a Boiler Using Fuzzy Logic Controller

Abstract

Presently used modern techniques to control instead of the traditional control techniques for many industrial applications virtually or theoretically. In this paper, a Fuzzy logic has been applied to control the important variable of steam generator i.e., drum level. It was used simulation of Fuzzy system in MATLAB program. The results showed that the adoption of control technique that based on Fuzzy logic have a high response to indicate the control signals and thus can be depended as an active control system for selecting a right decisions compared with traditional systems. A very common control problem, and one used in many examples elsewhere, is that of controlling the level in a boiler drum. Many industrial plants have boilers for generating process steam, and of course boilers are central to thermal power generation. The boiler drum is where water and steam are separated. Controlling its level is critical – if the level becomes too low, the boiler can run dry resulting in mechanical damage of the drum and boiler piping. If the level becomes too high, water can be carried over into the steam pipe work, possibly damaging downstream equipment. Steam boiler provides appropriate quality and quantity of steam to the turbine for power generation. In drum type boiler, water and steam flow in the drum is controlled in such a way that the water level in the drum is maintained fairly at a preset value. While very low water level in the drum may lead to starvation and explosion of boiler, too high level may cause carryover of water particle and damages the superheaters. Therefore Drum level is an important parameter for safe operation of a boiler. Drum level in a drum type boiler is influenced by number of factors, such as sudden change in load demand and changed in heat input to the boiler etc. During Boiler Feed Pump (BFP) runback, the boiler steam generation is reduced through fuel cut off while steam out flow to the turbine is controlled by pressure controller. Under such circumstance, due to mismatch between steam out and feed water in, it becomes difficult in maintaining water level in the drum to its pre set value. This paper has suggested an innovative drum level control by adopting the Fuzzy controller. It module uniquely co- relates two independent time varying parameters namely steam flow and feed water flow in real time and accordingly apply correction of steam flow to match steam and water flow during BFP runback. Simulation result shows real time correction of steam flow maintains drum level within its safe operating limit during BFP runback. The innovative related rate module can be used as a control block in the future boiler controls for coordination between many parameters varying independently with respect to time. The adoption of fuzzy logic in control system gave the ability to take on decision for control signals with a high stability compared with traditional methods. The fuzzy system contributed in giving prophesies for station case to tell the operator what to do therefore enhancement the performance of station through to take a right decision to avoid stopping.