一對一與一對多空調系統之鑑別與控制

Identification and Control of Single and Multi-Evaporator Air-Conditioning Systems

林金龍(Jin-Ling Lin)

指導教授 ： 葉廷仁

國立清華大學/工學院/動力機械工程學系/博士(2008年)

https://doi.org/10.6843/NTHU.2008.00279

摘要

In this thesis, feedback controller designs are proposed for modern air-condition -ing systems which contain either single evaporator or multiple evaporators. For the single-evaporator air-conditioner, the feedback controller possesses a cascade structure for dealing with the fast and slow dynamics in the system. To determine appropriate control parameters, conditions that establish performance and stability are given. A dynamic compensator is also incorporated into the controller to reduce the performance degradation caused by the low-speed limit of the compressor. Experiments demonstrate that the proposed control system can simultaneously provide better regulation for the indoor temperature and improve the energy efficiency at steady state. For the multi-evaporator air-conditioner, a control strategy with flow-distribution capability is proposed to accommodate different thermal demands in different rooms. To determine appropriate control parameters, theorems regarding stability of the closed-loop system are also given. Experiments indicate that the proposed strategy can successfully regulate the indoor temperatures regardless that the reference settings for respective rooms are different and the settings are switched in the middle of the control process. Because the multi-evaporator air-conditioning machine can be operated in modes that only selected evaporator(s) is(are) turned on, when mode-switching is demanded, switching directly from one control strategy to another could lead to discomfort to the users. Therefore, the thesis also proposes a framework for the mode switching control of the multi-evaporator air-conditioning system. The framework is an integration of cascading control structure based on the flow distribution and a dynamic compensator. In the framework, only the controller that all the evaporators are on throughout the control process is used to provide the nominal performance, and the dynamic compensator can account for the influence when the mode switching operation occurs. Experiments also indicate that the proposed framework can provide satisfactory mode-switching performance.

關鍵字

空調系統 ； 串聯控制 ； 系統鑑別 ； 多蒸發器系統 ； 動態切換策略 ； 模式切換 ； 分流控制

並列摘要

HASH(0x1a847a10)

並列關鍵字

air-conditioning system ； cascade control ； system identification ； muti-evaporator system ； dynamic switching strategy ； mode switching ； flow distribution control

參考文獻

[3] M. Hattori, et. al., Automotive refrigeration system controller with a simple precompensator, in: Proceedings of the 29th Conference on Decision and Control, USA (1990) 1590-1591.

[4] W. A. Miller, Steady-state refrigerant flow and airflow control Experiments for a continuously variable speed air-to-air heat pump, ASHRAE Transactions 93(2) (1987) 1191-1204.

[5] G. L. Wedekind, B. L. Bhatt and B. T. Beck, A system mean void fraction model for predicting various transient phenomena associated with two phase evaporating and condensing flows, International Journal of Multiphase Flow 4 (1978) 97-114.

[6] E. W. Grald and J. W. MacArthur, A moving-boundary formulation for modeling time-dependent two-phase flows, International Journal of Heat & Fluid Flow 13(3) (1992) 266-272.

[7] B. D. Rasmussen and A. G. Alleyne, Control-orented modeling of transcritial vapor compression systems, Transaction of the ASME: Journal of Dynamic Systems, Measurement, and Control 126 (2004) 54-64.