model based control of refrigeration containers kresten kjær sørensen lodam electronics a/s and...
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Model Based Control of Refrigeration Containers
Kresten Kjær Sørensen
Lodam electronics a/s and
Aalborg University
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Outline• Developmental, commercial and scientific
objectives
• System overview
• Project status
• Issues that should be addressed
• Research
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Developmental Objectives
“A set of methods that enable optimal, adaptive, constrained control of a refrigeration container that is also applicable to other thermodynamical systems”
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Commercial Objectives
• Better competitiveness through:– Reduced energy consumption– Reduced mechanical wear and tear – Improved adaptiveness of the controller
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Scientific Objectives
• To use MPC for refrigeration by:– Finding a suitable method for modeling
nonlinear dynamics of the refrigeration system that may be used by an MPC.
– Finding a method to cope with changes in system dynamics in the event of failure.
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
System overview
• Known refrigeration system dynamics
• Unknown cargo dynamics
• Known constraints on cargo temperature
• Economizer gives an additional degree of freedom
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Log(p)-h Diagram
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Project Status
• A library of nonlinear refrigeration component models has been developed.
• A composite simulation model has been developed.
• A framework that allows to test a controller, working within Matlab, with real hardware is ready.
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Simulation Model 1/2
• Nonlinear simulation model of the refrigeration system.
• Composed of smaller component models from a library.
• Simulation is done in Matlab by a set of custom functions.
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Simulation Model 2/2
Simulation Model.xml
Component1.xmlComponent1.m
Component4.xmlComponent4.m
Component2.xmlComponent2.m
Component3.xmlComponent3.m
• The simulation model is described by a number of files
• Each component are simulated separately for a short time step
• All outputs at the end of the simulation is propagated to the relevant inputs
• Simulation run again for another time step
• Equivalent of simulating a large, combined function with ZOH’s inserted between components
Lodam electronics a/s · Kærvej 77 · DK-6400 Sønderborg · Tlf. +45 73 42 37 37 · Fax +45 73 42 37 30 · www.lodam.com
Issues that must be addressed• The system is nonlinear and has a large
area of operation for both hot and cold temperatures.
• There are discrete actuators with strong influence on the dynamics that cannot be neglected.
• In case of partial system malfunction it is very important to continue cooling.