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VODENJE SINHRONSKEGA STROJA S TRAJNIMI MAGNETI Z UPOŠTEVANJEM TEMPERATURE ROTORJA
ID Uršič, Luka (Author), ID Nemec, Mitja (Mentor) More about this mentor... This link opens in a new window

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Abstract
V doktorski disertaciji je predstavljena celostna rešitev vodenja sinhronskega stroja s površinsko nameščenimi trajnimi magneti pri visokih temperaturah in v področju slabljenja polja. Rešitev je zastavljena kot dopolnitev osnovne regulacijske sheme FOC in ne predvideva dodatnih prilagoditev strojne opreme. Prav zaradi tega se smatra kot cenovno ugodna in relativno preprosta nadgradnja obstoječega sistema. Uvodoma se seznanimo s pregledom različnih področij, ki so del raziskave. Od načinov ocenjevanja trenutne vrednosti vrtilnega momenta, preko modeliranja razmagnetenja in ukrepov zaščite pogona sledi opredelitev problema, ki kaže na problematiko vodenja strojev pri povišanih temperaturah in področju slabljenja polja. Z opredelitvijo splošnih enačb sinhronskega stroja s trajnimi magneti in vodenja le-tega po teoriji orientacije polja, predvsem v področju slabljenja polja, se zaradi poenostavitve in zato bolj nazorne obravnave problema, raziskava nasloni na tip stroja z neizraženimi poli. Iskanje vzroka padcu zmogljivosti stroja pri povišani temperaturi in ustrezne ocene trenutne vrednosti vrtilnega momenta so začetne smernice pričujočega dela. Iz tega se tema razvije na področje lastnosti trajnih magnetov in možnosti njihovega razmagnetenja, kar skupaj z izpeljavo modela razmagnetenja predstavlja zajeten del raziskave. Daljše in osrednje poglavje predstavlja obravnavo problema razmagnetenja z metodo končnih elementov, s pomočjo katere je nato osnovana ustrezna magnetna struktura za izpeljavo magnetnega vezja. Rezultati iz metode končnih elementov služijo za preverjanje delovanja magnetnega vezja ter opredelitev njegovih omejitev. Magnetno vezje nato postane osnova za določitev statorskega razmagnetilnega magnetnega polja, ki vpliva na trajne magnete. Z modificiranim opazovalnikom magnetnega pretoka trajnih magnetov je določena njihova temperatura, preko tega pa tudi njihova trenutna delovna točka. Z modelom razmagnetenja je nato opisana razmagnetilna krivulja trajnih magnetov, nanjo pa postavljena ocenjena trenutna delovna točka. Iz tega sledi določitev oddaljenosti delovne točke od kolena krivulje in s tem ustrezna omejitev toka slabljenja polja, da bi delovno točko ohranili v reverzibilnem področju delovanja trajnih magnetov. Poglavje o rezultatih predstavlja delovanje sistema tako v simulacijskem kot tudi v praktičnem laboratorijskem modelu. Rezultati, ki so pridobljeni v dveh režimih, to je pri konstantnem slabljenju polja in naraščajoči temperaturi ter pri konstantni temperaturi in progresivnem slabljenju polja, kažejo na ustreznost ocene trenutne vrednosti vrtilnega momenta na gredi stroja in zaščite pred razmagnetenjem trajnih magnetov. Dodatno je z natančno oceno vrtilnega momenta omogočena tudi njegova kompenzacija v primeru padca lastnosti trajnih magnetov, zaradi naraščajoče temperature. Za nazornejšo ilustracijo premikanja delovne točke trajnih magnetov po B(H) karakteristikah so na koncu prikazani tudi 3D grafi v obeh delovnih režimih, kjer so zbrani rezultati simulacij in meritev. Na njih lahko opazujemo delovanje zaščite pred razmagnetenjem, kjer delovna točka ostaja v področju reverzibilnosti, in kako v primeru odsotnosti zaščite delovna točka trajnih magnetov zaide pod koleno B(H) krivulje v ireverzibilno področje razmagnetenja. Sklepno poglavje kratko povzame potek dela, opredelitev glavnih značilnosti in nakazuje na možnost nadaljnega razvoja predlaganega sistema, predvsem na področje sinhronskih strojev s trajnimi magneti in izraženimi poli.

Language:Slovenian
Keywords:Sinhronski stroji s trajnimi magneti, ocena trenutne vrednosti vrtilnega momenta, lastnosti trajnih magnetov, razmagnetenje, matematični model razmagnetilne krivulje, delovna točka trajnih magnetov, magnetno vezje, ocena temperature trajnih magnetov
Work type:Doctoral dissertation (mb31)
Organization:FE - Faculty of Electrical Engineering
Year:2021
Publication date in RUL:25.02.2021
Views:407
Downloads:126
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Secondary language

Language:English
Title:CONTROL OF PERMANENT MAGNET SYNCHRONOUS MACHINE CONSIDERING ROTOR TEMPERATURE
Abstract:
The thesis presents complete solution for control and management of permanent magnet synchronous machine at elevated operating temperatures with torque estimation and field weakening mode. The solution is made as an expansion of basic FOC scheme and does not need any hardware modifications. As a result it can be considered a cost-effective and relatively simple upgrade to existing control system. Introduction of the thesis provides the overview of different areas considered in this research, from torque estimation, drive protection measures and demagnetization modelling followed by a problem definition of controlling the electric drive at elevated temperatures. After the definition of general model equations of permanent magnet synchronous machine and presentation of field oriented control in field weakening mode, the thesis focuses on non-salient pole type of machine. The main reason for this is the simplification of the problem approach. Decreased performance of machine at elevated temperatures and the corresponding machine torque estimation are the initial guidelines of the present work, following from permanent magnet material properties. Demagnetization mechanism, together with demagnetization modelling represent a great part of the thesis. Central and longest chapter deals with modeling of demagnetization with finite element method, through which an appropriate magnetic structure for simplified magnetic circuit is derived. The results from both the magnetic circuit and finite element method are compared to justify the accuracy of proposed magnetic circuit. The stator reverse field estimation, which directly affects the permanent magnets, is determined using the magnetic circuit approach. The permanent magnet temperature is determined with simple modified flux observer. Using both the permanent magnets temperature and magnetic circuit, the permanent magnets operating point on B(H) curve is obtained. Followed by calculation of safe operating area, which is defined as the distance between current operating point of permanent magnets and the knee point of B(H) curve, the stator field weakening current is limited to prevent their demagnetization. The results chapter presents the operation of proposed system in both simulations and in practical laboratory model. Results are obtained in two regimes, namely at constant field weakening operation and a rising temperature of permanent magnets and at constant temperature and progressive field weakening. The efficiency of proposed torque and temperature estimation method along with the permanent magnet demagnetization protection mechanism are presented. It is also shown that the accuracy of torque estimation enables the compensation of the decreased torque generation due to thermal effects. For a clearer illustration of position of the operating point of permanent magnets according to B(H) characteristics, 3D graphs in both regimes are also shown at the end of the chapter. The results of both the simulation and laboratory model are gathered together on the same graph to better present their correspondence. It can be seen how the operating point stays within reversible demagnetization area in case of active demagnetization protection and how in the absence of protection the operating point shifts below the knee of B(H) characteristics into the irreversible demagnetization. The final chapter briefly summarizes the work and definition of its main features and indicates the possibility of further work development of the proposed system. Particularly, the salient pole permanent magnet synchronous machines are to be considered in the future work in this field.

Keywords:Permanent magnet synchronous machines, load torque estimation, properties of permanent magnets, demagnetization, modelling of demagnetization, permanent magnet operating point, magnetic circuit, permanent magnet temperature estimation

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