Model parameter identification of indoor temperature lag characteristic based on hysteresis relay feedback control in VAV systems

Abstract

The dynamic regulation process of variable air volume (VAV) systems is a typical nonlinear process, which has characteristics of multi-variable, strong coupling, and large lag. Due to the lag response characteristics of indoor temperature versus system regulation variables, it is difficult to accurately describe indoor temperature dynamic regulation characteristics based on a conventional open-loop step response test. Taking indoor temperature lag characteristic of the air conditioning system as the study object, this paper brings hysteresis relay feedback control (HRFC) into the model parameter identification of indoor temperature lag characteristic, and provides a novel method for indoor temperature lag characteristic identification of the air conditioning system. This study provides the detail implementation process of the proposed identification method. Supported by the comparative experimental study, the effectiveness and practicability of the proposed method is validated in an integrated control test rig for a VAV system. Under the condition of no prior knowledge, model parameters of indoor temperature first-order inertia plus lag link transfer function could be identified based on HRFC accurately. Results indicate that inertial time coefficients and pure lag time coefficients are convergent. The key contribution of this paper is to propose an online identification method for indoor temperature lag characteristic in dynamic regulation process of VAV system. It's worth noting that the proposed method may be invalid if the indoor temperature changes greatly due to some uncertainty large disturbances, however it is useful for new-built VAV system during the commissioning process.