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Author:Oksanen, Janne Matias
Title:Performance assessment of the multivariable MPC controller
Monimuuttujasäädön suorituskyvyn mittaaminen ja monitorointi
Publication type:Master's thesis
Publication year:2012
Pages:xiv + 116 + [15]      Language:   eng
Department/School:Kemian laitos
Main subject:Prosessien ohjaus ja hallinta   (Kem-90)
Supervisor:Jämsä-Jounela, Sirkka-Liisa
Instructor:Yli-Opas, Keijo ; Bergman, Samuli
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  1938   | Archive
Keywords:MPC
peformance assessment
MIMO
suorituskyky
monimuuttujasäätö
Abstract (eng): Recently, there has been an increase in the demand of MPC controllers in the oil refining and petrochemical industry in order to improve process profitability, stability and safety.
The performance assessment of the controller should be carried out to ensure it is operating properly and efficiently.
The aim of this thesis is to develop a reliable and accurate application with the ability to compute the technological and economic performance of the MPC controller.
The purpose is to produce valid information about the state of the process based on the performance of the controller.
Further conclusions and preventive actions can be executed if the performance is poor according to the application.
These preventative control actions are essential in minimizing profit loss.

The literature part of this thesis consists of three main chapters.
In the first chapter, the fundamentals of the MPC controller are introduced.
The second chapter discusses different issues that have an influence on the performance of the MIMO MPC controller.
The third chapter covers the techniques that are used to compute the performance of the MIMO MPC controller.

In the experimental part of this thesis, the focus is on designing and developing economic and technological performance indices to the constrained, multivariable MPC controller.
To achieve this, two methods were chosen from the literature; the first was a method based on analysis of historical process data and the second was the design case approach.
Both methods were further developed to compute performance indices including data from the past, present and future.
The technological performance was deduced by computing two abovementioned indices in parallel and using the average value of them as the technological performance index.
The economic performance was computed by utilizing the historical benchmark method and the short-term profit.
Several applications, proprietary of Neste Jacobs, were used to create and simulate the indices in the testing environment.
Furthermore, the process was simulated as realistically as possible by exploiting the real process data, which was collected from the benzene distillation process in the petrochemical plant of Borealis.

Many different simulation cases were used to examine how the designed application responds to different situations.
In the simulations, the application provided valuable information indicating the current performance of the controller.
The design case index was able to distinguish the presence of abrupt changes in the process which usually decreases the performance.
Also the historical index produced valid information about the state of the controller so that the user can infer if the controller is operating appropriately.
Moreover, the results of the simulations proved that when the technological performance is at the desired level, the economic performance is high as well.
Abstract (fin): Pyrkimys parempaan prosessin kannattavuuteen, stabiilisuuteen sekä turvallisuuteen on kasvattanut malliprediktiivisten säätimien kysyntää viime aikoina huomattavasti öljy- ja petrokemian teollisuudessa.
Mittaamalla säätimen suorituskykyä voidaan varmistaa säätimen tehokas ja oikeanlainen toiminta.
Tämän diplomityön tavoitteena on kehittää luotettava sovellus. joka mittaa monimuuttujasäätimen teknistä ja taloudellista suorituskykyä.
Sovelluksen avulla tuotetaan tietoa prosessin ja säätimen nykytiloista, joiden pohjalta käyttäjä voi päätellä, toimiiko säädin hyvin.
Havaitessaan huonon suorituskyvyn käyttäjä voi ryhtyä ennaltaehkäiseviin toimenpiteisiin. jolloin säätimen heikosta suorituskyvystä johtuvat tappiot saadaan minimoitua.

Tämän työn kirjallisuusosa koostuu kolmesta pääkappaleesta.
Ensimmäinen kappale käsittelee malliprediktiivisen säätimen perusteita.
Tekijät, jotka vaikuttavat monimuuttujasäätimen suorituskykyyn, esitellään toisessa kappaleessa.
Kolmas kappale esittelee erilaisia tekniikoita MIMO-malliprediktiivisen säätimen suorituskyvyn mittaamiseen.

Kokeellinen osa keskittyy säätimen taloudellisen ja teknisen suorituskyky-indeksien suunnitteluun ja niiden kehittämiseen.
Suorituskyky-indeksien laskentaan valittiin kirjallisuudesta kaksi eri menetelmää; design-malliin ja historiaan perustuvat laskentatekniikat.
Menetelmiä jatkokehitettiin kuvaamaan kokonaisvaltaisesti säätimen suorituskykyä.
Teknologinen suorituskyky johdettiin laskemalla kahta edellä mainittua indeksiä rinnakkain ja käyttämällä niiden keskiarvoa suorituskykynä.
Taloudellisen suorituskyvyn laskentaan sovellettiin historiaan perustuvaa menetelmää sekä lyhyen aikavalin taloudellista tuottoa.
Indeksien testaamiseen ja kohdeprosessin simuloimiseen käytettiin Neste Jacobsin kehittämiä sovelluksia.

Työssä suunniteltua sovellusta testattiin monessa erilaisessa simuloinnissa, jotta voitiin tutkia, miten indeksit reagoivat eri tilanteisiin.
Kohdeprosessina oli bentseenin ja tolueenin tislausprosessi, joka pyrittiin simuloimaan mahdollisimman todenmukaisesti.
Simuloinneista saatujen tulosten perusteella voitiin selkeästi havaita säätimen teknisen ja taloudellisen suorituskyvyn muuttuminen sekä rajoitteiden aktivoituminen.
Design-malliin perustuva indeksi reagoi voimakkaasti tilanteisiin. joissa prosessin tila muuttui äkillisesti.
Myös historiaan perustuvan indeksin avulla voitiin erottaa säätimen heikko suorituskyky.
Tulosten pohjalta voitiin myös huomata. että teknisen suorituskyvyn ollessa hyvä myös taloudellinen suorituskyky on korkea.
ED:2012-10-03
INSSI record number: 45334
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