Identification and Control of Multi-Evaporators Air-Conditioning System

J.-L. Lin, T.-J. Yeh, and Y.J.P. Lin (Taiwan)


Multi-evaporator air-conditioning systems (MEAC), Sys tem identification, Cascade control.


Modern multi-evaporator air-conditioners (MEAC) incor porate variable-speed compressors and variable-opening expansion valves as the actuators for improving cooling performance and energy efficiency. These actuators have to be properly feedback-controlled; otherwise the systems may exhibit even poorer performance and efficiency than the conventional machines which use only fixed-speed compressors and capillary-type expansion valves. In this paper, feedback controller design for the MEAC system is first addressed through systematic identification. The identification procedure produces a low-order, linear model suitable for controller design. The feedback controller em ployed is multi-input-multi-output-based and possesses a cascade structure for dealing with the fast and slow dy namics in the system. To determine appropriate control parameters, conditions that establish the stability for the cascade design are given. The control experiments indi cate that the proposed controller can successfully regulate the indoor and superheat temperatures.

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