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Model-free control and automatic staging of variable refrigerant flow system with multiple outdoor units.

Number: pap. 2600

Author(s) : DONG L., LI Y., SALSBURY T. I., et al.

Summary

This paper describes a model-free control and automatic staging strategy for the operation of a variable refrigerant flow (VRF) system with multiple outdoor units (ODUs). The strategy maximizes energy efficiency in real time and handles ODU operation during load changes. Extremum seeking control (ESC) is used to minimize power consumption in real time while the thermal load is regulated with inner loop controllers. In addition to the compressor pressure setpoints and ODU fan speeds, the manipulated inputs of ESC include the openings of suction-side bypass valves in order to optimize load sharing among multiple ODUs. An integrated ODU staging-off strategy is proposed, for which the compressor shaft power normalized by the rated capacity is adopted as the feedback signal for ESC. Under decreasing load, it is desirable to turn off the least efficient ODU in a model-free fashion. The ODU compressor speed is proposed as the indicator variable for turning off the least efficiency ODU(s). In this study, with online optimization of ODU load sharing based on the normalized compressor power, ESC can drive less efficient compressor(s) to operate at lower speed/capacity.

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Pages: 8

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Details

  • Original title: Model-free control and automatic staging of variable refrigerant flow system with multiple outdoor units.
  • Record ID : 30024665
  • Languages: English
  • Source: 2018 Purdue Conferences. 17th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2018/07/09

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