Korean Journal of Air-Conditioning and Refrigeration Engineering (설비공학논문집)

The Society of Air-Conditioning and Refrigerating Engineers of Korea (대한설비공학회)
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State Equation Modeling and the Optimum Control of a Variable-Speed Refrigeration System

가변속 냉동시스템의 상태방정식 모델링과 최적제어

  • Lee, Dan-Bi (Graduate School of Refrigeration and Air-conditioning Engineering Pukyong National University) ;
  • Jeong, Seok-Kwon (Department of Refrigeration and Air-conditioning Engineering, Pukyong National University) ;
  • Jung, Young-Mi (Department of Refrigeration and Air-conditioning Engineering, Pukyong National University)
  • 이단비 (부경대학교 대학원 냉동공조공학과) ;
  • 정석권 (부경대학교 냉동공조공학과) ;
  • 정영미 (부경대학교 냉동공조공학과)
  • Received : 2013.02.13
  • Accepted : 2014.10.02
  • Published : 2014.12.10
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Abstract

This paper deals with precise analytical state equation modeling of a variable speed refrigeration system (VSRS) for optimum control in state space. The VSRS is described as multi-input and multi-output (MIMO) system, which has two controlled variables and two control inputs. First, the Navier-Stokes equation and mass flow rate were applied to each component of the basic refrigeration cycle to build a dynamic model. The dynamic model, represented by a differential equation, was transformed into the state equation formula. Next, a full-order state observer was built to estimate all of the state variables to compose an optimum control system. Then, an optimum controller was designed to minimize an evaluation function that has input energy and control error. Finally, simulations and experiments were conducted to verify the validity of the proposed modeling and designed optimum controller to regulate target temperature and superheat in a 1RT oil cooler system. The results show that the proposed method, state equation modeling and optimum control, is efficient to ensure optimal control performance of the VSRS.

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References

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