Performance Comparison of Cascade Control with Conventional Controls in Air-Handling Units for Building Pressurization (OR-16-C068)

Buildings are maintained at slightly positive pressure by the air handling units to avoid infiltration of unconditioned air. The conventional AHUs rely either on direct building pressure control or volume tracking control with a single loop proportional integral derivative controller to maintain positive building pressure. Even though this type of control structure is simplistic, the performance is usually not satisfactory. The purpose of this paper is to evaluate the performance of the cascade control on the building static pressure in comparison with the two conventional controls by simulation. An airflow model of an AHU system with PID controllers is developed. Performance of the two conventional controls as well as cascade control is simulated and subjected to wind effect, pressure fluctuations and flow sensor error.  The simulations conclude that the cascade control method stabilizes the control signal and compensates the error in flow measurement.