Biomass-fired Boiler Control Using Simulated Annealing Optimized Improved Varela Immune Controller

Water temperature control of biomass-fired boilers represents a process with extreme delay which makes it quite difficult to stabilize it using conventional PID controller tuned according to commonly used PID tuning rules. It is proposed here to use a controller based on Varela-Countinho second generation immune network which was shown to have very good anti-delay capabilities. Since there are currently no tuning rules for this type of controller, simulated annealing algorithm is used for optimizing the set of controller parameters to achieve good performance according to IAE criterion. The resulting controller is shown to offer stable performance even for such a long time-delay which is also robust for up to 30% variations in system time constant compared to a nominal case.