Model-based robust temperature control for VAV air-conditioning system

VAV air-conditioning systems are widely used in modern buildings and cascaded PIDcontrollers, including an inner loop and an outer loop, are usually equipped to control zone temperature to track a set point for thermal comfort. Since the outer-loop PID controller with fixed parameters lacks robustness to deal with cooling load variations, this paper proposes a model-based robust temperature control strategy as an alternative and addresses its year-round application. The proposed strategy has three control modes, each of which is used to realize different control objective. The integration of the three modes is developed to deal with directly the bilinear relationship between the zone temperature and the supply air flow rate, the constraint on the operation range of the supply air flow rate and the year-round variations of the zone cooling load. Case studies are performed to show that without online tuning of its control parameters, the triple-mode control can track the set point well and achieve a good robustness under different load conditions. © 2012 2012 ASHRAE.