Research on a hierarchical air balancing control method of variable air volume ventilation system

This paper proposes a hierarchical air balancing control method for the ventilation system, which implements a dual loop PID control loop on a layered system structure. A set of fan-duct PID design methods are proposed, which can be programmed to realize automatic design in microcomputer, including determining the transfer function as a first-order plus time delay model, open-loop characteristic test with two points method and self estimation of PI parameter. The negative open proportional characteristic of the damper is discovered. Based on this fact, the first-order plus time delay mode is used to build the damper transfer function too, and the same estimation method of fan-duct is adopted to estimate the PI parameter. A two-step action way of angle adjustment is presented to avoid the mechanical error and achieve better response characteristics while implementing the damper PID control. The experiments demonstrate that the proposed air balancing method is correct and effective and has the ability to achieve control objectives. Moreover, this method has good adaptability and can be applied to different VAV ventilation system to realize variable air volume control.