Optimisation and dynamic effect of slip couplers in geared wind drivetrains

Britz, Joseph Juan (2019-04)

Thesis (MScEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Two electromagnetic (EM) torque couplers, which are referred to as slip couplers, are designed and optimised to be placed in a 2.2 kWwind turbine drivetrain. These slip couplers make the drivetrain more robust, by filtering unwanted torque oscillations. The slip coupler performance is evaluated using EM finite element method (FEM) software, implemented in a Python/Semfem script. The slip coupler is a polyphase electric machine, and a dq inductance estimation method is used to solve for different static rotor steps iteratively. Both slip coupler designs are optimised using genetic and gradient-based algorithms. The NSGA-II and MMFD optimisation algorithms are utilised in the Visualdoc environment, to minimise the total mass of the design. The optimisation constraints and influence of the design variables are evaluated using a colour-graded Pareto and dominated-solution space. One of the slip coupler designs improves upon a similar design found in literature, because the NSGA-II was used together with the MMFD optimisation algorithm. A time-transient analysis of both slip couplers is performed using Ansys Maxwell, and the currents and flux-linkage values compare well with Semfem. The torque ripple values generated by Maxwell casts doubt on some of the results and indicates that another EM-FEM software suite should be used. Finally, the wind turbine is modelled using Matlab Simulink, and the unforced and steady-state response to a wind gust and tower shadow component is determined. A two-mass drivetrain model, with flexible shafts going into and out of the gearbox, is tested. In conclusion, a slip coupler, when placed on the turbine side of the drivetrain, reduces higher-frequency torque vibrations and may be a viable wind turbine component in future designs.

AFRIKAANSE OPSOMMING: Twee elektromagnetiese (EM) draaimoment-koppelaars, oftewel glipkoppelaars, word ontwerp en ge-optimeer vir gebruik in ’n 2.2 kW wind turbine assestelsel. Die glipkoppelaars maak die assestelsel meer robuus, deur ongewensde draaimoment ossilasies te filter. Die glipkoppelaar word ge-evalueer met ’n EM eindige-element metode (EEM) sagteware pakket, wat ge-implementeer word in Python/Semfem. Die glipkoppelaar is ’n multifase elektriese masjien, en word ge-analiseer met ’n dq induktansie estimasie metode. Dié metode los die strome in die masjien iteratief op, vir statiese rotor stappe. Die NSGAII en MMFD optimerings algoritmes word toegepas in Visualdoc en die totale massa van die masjiene word geminimaliseer. Die optimeringsbeperkinge en invloed van ontwerpsveranderlikes word ge-evalueer deur ’n kleur-gradiëring toepassing op die Pareto- en domineerde-oplossings spasies. Een van die glipkoppelaars verbeter ’n soortgelyke ontwerp in die literatuur, omdat die NSGA-II tesame met ’n MMFD algoritme gebruik was. Die tyd oorgangstoestand van beide glipkoppelaars word gesimuleer in Ansys Maxwell, en die stroom- en vloedomsluitingswaardes lyk eenders as dié van Semfem. Weens ’n verskil in Maxwell se draaimoment-riffel waardes, word ’n ander EM-EEM sagteware pakket voorgestel vir verifiering. Laastelik, die wind turbine word gemodelleer in Matlab Simulink en die vry- en bestendige assestelsel reaksie tot rukwind en toringskadu toestande word gesimuleer. ’n Twee-massa model, met buigbare aste wat aan weerskante van die ratkas sit, word getoets. Ten slotte, ’n turbine-kant glipkoppelaar verminder hoër-frekwensie draaimoment vibrasies wat op die aste inwerk, en dié ontwerp kan moontlik ’n aanwins in enige wind turbine stelsel wees.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105953
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