Regulacija vrtilne hitrosti elektromotorskega pogona z indukcijskim motorjem

Rebrica, Iztok (author), Nedeljković, David (mentor), Rihar, Andraž (comentor)

Asinhronski motorji dandanes nastopajo v številnih elektromotorskih pogonih tako v industrijskih kot tudi v drugih aplikacijah. Čeprav so robustne zgradbe, pa so njihovi matematični modeli lahko zelo kompleksni, saj vsebujejo težko rešljive diferencialne enačbe. Zato si pri razvoju regulacijskega sistema pomagamo s simulacijskimi programi, ki omogočajo vpogled v razna obratovalna stanja stroja, tudi tista, ki jih fizično ne moremo izmeriti, ter preverjanje ustreznosti regulacijskih algoritmov. V tej nalogi je za simuliranje napetostno vodenega asinhronskega motorja s kratkostično kletko (indukcijskega motorja) bil uporabljen program MATLAB Simulink. Model temelji na dvoosni d-q teoriji, pri kateri trifazni model stroja pretvorimo v dva enosmerna sistema (to velja za ustaljeno obratovanje). To se stori preko dq0 transformacije, ki pretvori trifazne tokove ter napetosti v enosmerne veličine, kar model bistveno poenostavi. Regulacijski sistem temelji na metodi posredne vektorske regulacije (angl. "indirect field oriented control"), realiziran pa je bil s kaskadno regulacijo, ki poteka po dveh glavnih regulacijskih zankah, kjer vsaka vsebuje še eno podrejeno zanko. Ena glavna zanka skrbi za regulacijo magnetilnega toka imR, s podrejeno zanko za regulacijo statorske komponente toka iSd. Druga glavna zanka regulira vrtilno hitrost rotorske gredi. Njej podrejena zanka je namenjena regulaciji statorske komponente toka iSq. V nadrejenih zankah sta bila uporabljena PI regulatorja, v podrejenih pa sta z namenom stabilizacije statorskih tokov bila uporabljena PID regulatorja. Model, ki sem ga zgradil, omogoča tudi analizo vpliva spreminjanja parametrov motorja. Poudarek je bil na spreminjanju statorske ter rotorske upornosti ter njunem vplivu na dinamiko stroja. Sprememba upornosti namreč privede do spremembe časovnih konstant navitij, kar lahko zaradi neskladja med modelsko vrednostjo upornosti in dejansko vrednostjo upornosti privede do nestabilnega delovanja pogona. Kot celota regulacijski sistem omogoča stabilno delovanje stroja v različnih delovnih točkah. Uporaba vektorske regulacije je privedla do visoke dinamike modela; torej so prehodi med obratovalnimi stanji relativno hitri. Povišanje upornosti (segrevanje) je imelo pozitiven učinek na dinamiko, vendar pa je regulacija ustrezno delovala tudi ob nerealnih zvišanjih rotorske in statorske upornosti. Za bolj realen model bi nadaljnje nadgradnje torej lahko vključile neko vrsto termične analize.

• Language: Slovenian
• Keywords: Indukcijski/Asinhronski motor, MATLAB Simulink, dvoosna d-q teorija, dq0 transformacija, posredna vektorska regulacija.
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FE - Faculty of Electrical Engineering
• Year: 2024
• PID: 20.500.12556/RUL-161525
• COBISS.SI-ID: 207230211
• Publication date in RUL: 12.09.2024

Secondary language

• Language: English
• Title: Speed control of an electric drive with an induction motor

Abstract

Asynchronous motors are nowadays used in many electrical drives, both in industrial and other applications. Although robust in design, their mathematical models can be quite complex, due to differential equations that are hard to solve. For this reason, simulation programs are used to develop the control system, as they give us the insight into various operating states of the machine, even those that are not measurable; additionally, they allow the validation of implemented control algorithms. In this thesis MATLAB Simulink was used for simulating a voltage-controlled asynchronous motor with a squirrel cage (induction motor). The model is based on the two-axis d-q theory, which converts a three-phase model of a machine into two DC systems (during steady state operation). This is done by using the dq0 transformation that transforms three-phase currents and voltages into DC quantities which drastically simplifies the model. Motor control is based on the indirect field-oriented control "FOC" method and is realized with cascade control, which is structured in two main control loops, with each having one subordinate loop. The first main loop controls the magnetizing current imR, with its subordinate loop controlling the stator current component iSd. The second main loop controls the speed of the rotor shaft. Its subordinate loop controls the stator current component iSq. Two PI controllers are used in main loops, while two PID controllers are used in subordinate loops to improve the stability of stator currents in the machine. The presented model also allows me to analyse the impact of changing motor parameters. The focus was on the variation of the stator and rotor winding resistance and their effect on the dynamics of the machine. Changing the winding resistance leads to a change in winding time constants, which can lead to unstable operation of the drive due to the difference between the actual resistance from its estimated model value. The control system ensures a stable operation of the machine in various operating points. The use of field-oriented control led to high model dynamics; therefore, the transitions between operating points were relatively quick. The increase of resistance (heating) had a positive effect on dynamics, though the control system worked adequately even with unrealistic increases of rotor and stator resistances. For a more realistic model, further development in the field of thermal analysis should be considered.

• Keywords: Induction/Asynchronous motor, MATLAB Simulink, two axis d-q theory, dq0 transformation, indirect field-oriented control (FOC).