PERFORMANCE COMPARISON OF PI AND FUZZY LOGIC CONTROLLER OF A HEAT RECOVERY STEAM GENERATOR

Recently, energy consumption is getting increased rapidly. However, the
sources of energy nowadays are limited and the demand is getting increased in the
course of time. Heat recovery steam generator or HRSG is one of the big equipment
that is productively being used these days to recover the heat and to produce it into
steam that can be used in many applications. However, it is known that HRSG is a
complex system and using conventional controller to control the system has brought
a lot of drawbacks. Providentially, the requirements for fast and flexible responses
along with the increasing complexities of modern plant process control applications
has motivated new enhancements and works in the invention of various control
techniques in many process plant and Fuzzy logic is known as one of the technique
available. This project aims to develop a control strategy using a fuzzy logic
controller to be used as a pressure controller to control the input of the Heat recovery
steam generator (HRSG) model which is the exhaust gas from a connected gas
turbine as per the steam demand and also as an alternative to the existing
conventional PI controller. The model of the heat recovery steam generator and the
designed Fuzzy logic controller is entirely developed by using the
MATLAB/Simulink software. The PID and Fuzzy Logic toolbox available in the
MATLAB Product Family is used to its full advantage in order to perform the
necessary simulations for the designed controllers. Mamdani approach is chosen in
order to develop the Fuzzy Inference System (FIS). The effectiveness, feasibility and
the performance of the designed fuzzy logic controller is studied through simulation
and the results are compared with the existing conventional PI controller. The
simulation results shows that a fuzzy logic controller developed in this study yields a
better performance compared to a PI controller in terms of settling time, overshoot,
final value, rising time and integral of absolute error.