Optimization of Double-Closed-Loop Control of Variable-Air-Volume Air-Conditioning System Based on Dynamic Response Model

Abstract

Control strategies for variable-air-volume (VAV) air conditioning significantly affect both the air quality within buildings and the consumption of building energy. Current control techniques effectively regulate room temperature using feedback on temperature discrepancies, yet they also elevate the wear on terminal devices and boost the energy usage of the supply fan. In this paper, the hysteresis and inertia parameters of end air valves and supply fans under two seasonal conditions are derived from experimental data. Aiming at the problems of frequent switching of the end air valve, long total switching stroke, and high energy consumption of the air supply fan, a fuzzy PI regulation method is proposed based on the original pressure-independent series PI regulation, which effectively solves the above problems. Initially, data on how room temperature reacts to changes in air supply fan speed and the position of end air valves during winter and summer were gathered. Following model identification, parameters for various seasonal conditions were determined. Secondly, the roles of different components in the variable-air-volume regulation process were investigated. Investigations revealed that within pressure-independent variable-air-volume control, the supply fan and end air valve emerged as the primary subjects of the study. A double-closed-loop control with the speed control of the supply fan as the outer loop and the opening control of the end air valve as the inner loop was adopted. Compared with the traditional serial PI regulation, the room temperature error of this method was increased, but it reduced the total stroke of the valve by more than 43%, which greatly reduced the valve’s loss and noise and saved more than 2.7% of the energy consumption of the air supply fan.