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Fuzzy logic PI controller with on-line optimum intermediate pressure for double-stage refrigeration system.

Author(s) : ESNOZ A., LÓPEZ GÓMEZ A.

Summary

The traditional control systems of a refrigeration compressor have usually been based on incremental PI controllers. Progress in the electronic implementation of this controller is immense, but the performance can still be improved. It is known that the PI controller is not the most efficient in systems in which the conditions change. On the other hand, in refrigeration systems with double-stage compression it is known that the selected intermediate pressure, usually the square root of the product of the evaporation and condensation pressure, is not the optimum in relation to the energy cost. The paper presents a new control system for these refrigeration systems and the Fuzzy Logic based Controller (FLC) is evaluated. The fuzzy logic has been used in a wide range of applications inside refrigeration systems. A FLC-PI has been used for the compressor control. This type of control has been chosen firstly because it is similar to the traditional PI and secondly since the FLC-PI has a no-linear behaviour. This usually implies a smooth and optimum performance. A new method to calculate the intermediate pressure is also presented. With this method the pressure is changed online, and it allows the energy costs to be minimized. In conclusion, it has been proven that with this new control system FLC-PI with optimum on-line intermediate pressure, and considering the same working conditions and temperature perturbations observed really in a frozen food factory, the energy consumption is reduced by 10% and the FLC-PI build is no more complex than a traditional PI controller.

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Details

  • Original title: Fuzzy logic PI controller with on-line optimum intermediate pressure for double-stage refrigeration system.
  • Record ID : 2005-0144
  • Languages: English
  • Source: 21st IIR International Congress of Refrigeration: Serving the Needs of Mankind.
  • Publication date: 2003/08/17

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