Internal model control used for feed water valve located at waste incinerator
Author
Olsen, Camilla Vind Malcho
Term
7. term
Education
Publication year
2023
Abstract
This project addresses control of a feed water valve in the steam cycle of the Esbjerg waste incinerator, where the condensate level in the separator tank must remain within specified alarm limits. The existing controller tightly tracks the level setpoint, causing frequent valve movements and increased wear, even though exact setpoint tracking is unnecessary as long as the level stays within an acceptable range. The objective is to design a control strategy that reduces valve sensitivity and motion while maintaining level within bounds. The approach includes a system analysis of the pump, control valve, three-way valve, economizers, separator tank, and level measurement; use of plant data; mathematical modeling of the separator and flow including valve characteristics; linearization and derivation of transfer functions; and Laplace-domain analysis. Based on this model, an internal model control (IMC) controller is designed and tested in simulations with step and disturbance inputs. The IMC-based controller is compared against the plant’s original PI control to assess smoother valve actuation and adequate level regulation aligned with operator requirements.
Dette projekt undersøger reguleringen af en fødevandsventil i dampkredsløbet på affaldsforbrændingen i Esbjerg, hvor kondensatniveauet i separatortanken skal holdes inden for fastsatte alarmgrænser. Den eksisterende regulering sporer setpunktet aggressivt og medfører hyppige ventilbevægelser og øget slitage, selv om et præcist setpunkt ikke er nødvendigt, så længe niveauet ligger inden for et acceptabelt interval. Formålet er at udforme en styring, der reducerer ventilens følsomhed og bevægelser, samtidig med at niveaugrænser overholdes. Tilgangen omfatter systemanalyse af pumpe, reguleringsventil, trevejsventil, economizere, separatortank og niveaumåling, anvendelse af anlægsdata, matematisk modellering af separatortank og strømningsforhold inkl. ventilkarakteristik, linearisering og afledning af overføringsfunktioner samt analyse i Laplace-domænet. Med udgangspunkt i modellen designes en internal model control (IMC) baseret regulator og afprøves i simulationer med trin og forstyrrelser. Den IMC-baserede regulator sammenlignes med den oprindelige PI-styring for at vurdere jævnere ventilbetjening og tilstrækkelig niveauregulering i forhold til operatørens krav.
[This apstract has been generated with the help of AI directly from the project full text]