A method for online steady state energy minimization, with application to refrigeration systems

Larsen, Lars Finn Sloth; Thybo, Claus; Stoustrup, Jakob; Rasmussen, Henrik

doi:10.1109/cdc.2004.1429534

Cited by 16 publications

(11 citation statements)

References 4 publications

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“…[9], [10], [11]. Superheating the refrigerant beyond the evaporation temperature is important, since no superheat means that two-phase refrigerant will enter the compressor and increase the power consumption and wear.…”

Section: System Nonlinearitymentioning

confidence: 99%

Utilization of excitation signal harmonics for control of nonlinear systems

Vinther

Rasmussen

Izadi‐Zamanabadi³

et al. 2012

2012 IEEE International Conference on Control Applications

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Abstract-Many model based control methods exist in the literature. Producing a sufficient system model can be cumbersome and a new non-model based method for control of nonlinear systems with input/output maps exhibiting sigmoid function properties is therefore proposed. The method utilizes an excitation signal together with Fourier analysis to generate a feedback signal and simulations have shown that different system gains and time constants does not change the global equilibrium/operating point. An evaporator in a refrigeration system was used as example in the simulations, however, it is anticipated that the method is applicable in a wide variety of systems satisfying the sigmoid function properties.

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Section: System Nonlinearitymentioning

confidence: 99%

Utilization of excitation signal harmonics for control of nonlinear systems

Vinther

Rasmussen

Izadi‐Zamanabadi³

et al. 2012

2012 IEEE International Conference on Control Applications

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“…The steady state value of the pressure given by the model c 2 f min f compṖ e = −P e +ṁ e α c f comp (15) is proportional toṁ e /α c . In the model verification section the uncertainty of α c was shown.…”

Section: New Control Methodsmentioning

confidence: 99%

“…Optimizing the set-points of these systems has been proved to enable a substantial reduction in the power consumption as shown in [1]. In [2] a method for on-line optimization of the set-points to minimize power consumption is presented. In a refrigeration system one of the key variables to control, which greatly affects the efficiency of the system, is the superheat.…”

Section: Introductionmentioning

confidence: 99%

Non-linear and adaptive control of a refrigeration system

Rasmussen

Larsen

2011

IET Control Theory Appl.

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In a refrigeration process heat is absorbed in an evaporator by evaporating a flow of liquid refrigerant at low pressure and temperature. Controlling the evaporator inlet valve and the compressor in such a way that a high degree of liquid filling in the evaporator is obtained at all compressor capacities ensures a high energy efficiency. The level of liquid filling is indirectly measured by the superheat. Introduction of variable speed compressors and electronic expansion valves enables the use of more sophisticated control algorithms, giving a higher degree of performance and just as important are capable of adapting to variety of systems. This paper proposes a novel method for superheat and capacity control of refrigeration systems; namely by controlling the superheat by the compressor speed and capacity by the refrigerant flow. A new low order nonlinear model of the evaporator is developed and used in a backstepping design of a nonlinear adaptive controller. The stability of the proposed method is validated theoretically by Lyapunov analysis and experimental results show the performance of the system for a wide range of operating points. The method is compared to a conventional method based on a thermostatic superheat controller.

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“…It should be noted that this work focuses on the control of the vapor compression cycle (VCC) itself; that is, the working of the refrigerant about some cycle such as shown in Figure 1 This cycle forms the basis for energy transfer and, in effect, becomes a critical inner loop to other higher level planning algorithms focused on overall outer loop control and optimization for enclosed environments such as [2]. In general, VCC systems are controlled to maximize the energy efficiency of the system while ensuring the fluid entering the compressor is in the vapor phase [3].…”

Section: Introductionmentioning

confidence: 99%

Feedback Structures for Vapor Compression Cycle Systems

Keir

Alleyne

2007

2007 American Control Conference

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This paper explores the controllability and interconnectedness of input-output relationships in vapor compression cycles. The magnitude of physical coupling between different outputs used in the feedback loop are examined. It is shown that an alternative to the conventional feedback configuration found in the literature has distinct benefits that allow for improved system regulation using simple classical control techniques. A relative gain array analysis technique is shown to be an effective method for identifying proper feedback configurations that maximize the controllability of vapor compression systems.

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A method for online steady state energy minimization, with application to refrigeration systems

Cited by 16 publications

References 4 publications

Utilization of excitation signal harmonics for control of nonlinear systems

Utilization of excitation signal harmonics for control of nonlinear systems

Non-linear and adaptive control of a refrigeration system

Feedback Structures for Vapor Compression Cycle Systems

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