Dynamics of a grid-connected small-scale geared wind turbine with slip-yynchronous technology

Ockhuis, Dillan Kyle (2018-03)

Thesis (MScEng)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: In this study, the dynamic behaviour of a 2.2 kW, fixed-speed downwind turbine is investigated. The downwind turbine drivetrain comprises of 1.9 m turbine blades, a gearbox with gear ratio of 1:3.78, a slip permanent magnet coupling and a permanent magnet synchronous generator (PMSG). The downwind turbine has a synchronous speed of 600 rpm (on the high-speed side of the gearbox) and is direct-grid connected by means of a grid connection controller (GCC). Each component of the downwind drivetrain was designed and developed by different persons however, the functionality of the drivetrain as a complete unit remains unknown. The 2.2 kW downwind drivetrain was modelled using mathematical equations which then translated to a simulation model using MATLAB/Simulink. From this simulation model, a transfer function model of the downwind drivetrain was determined by simulating a dynamic step-test. The transfer function of the downwind turbine was then used to design a speed controller using the Internal Model Control (IMC) tuning rules. The speed controller in conjunction with the GCC allows the downwind turbine to synchronize with and connect to the grid without the need for a power converter. The dynamics of connecting the simulated drivetrain to a grid is also evaluated using the developed simulation model. Furthermore, once grid connected, the on-grid dynamic performance of the downwind turbine was simulated and evaluated. Downwind turbines in particular are known to produce significant torque pulsations due to the tower shadow effect. The simulation model developed in this thesis is also used to simulate the effects of tower shadow and evaluates the effect on the resulting grid current. Furthermore, the simulation model also investigates and evaluates the dynamic behaviour of the grid-connected downwind turbine during various grid disturbances. The physical downwind turbine drivetrain was tested and evaluated on a mechanical testbench in the electrical machines laboratory. The laboratory testing included: . the implementation of the dynamic step-test on the physical downwind drivetrain, . testing the speed controller's ability to control and maintain the downwind drivetrain's speed at synchronous speed prior to grid connection, . autonomous grid connection using the grid connection controller, . investigations regarding the downwind drivetrain's sensitivity to torque pulsations at different frequencies and, . the overall functionality of the grid connection controller when the downwind drivetrain is subjected to above-rated conditions. The laboratory test results closely resembled their respective simulated test results which served as validation of the accuracy of the developed simulation model. The 2.2 kW downwind turbine was erected at the Stellenbosch University Mariendahl small wind turbine testing facility. However, due to unforeseen events and circumstances, no data could be collected with respect to the downwind turbine's on-site performance. However, the simulation model and laboratory tests suggests that the downwind turbine is on-grid stable and is unaffected by the torque pulsations caused by the tower shadow effect and could function on-site for future study.

AFRIKAANSE OPSOMMING: In hierdie studie word die dinamiese gedrag van 'n 2.2 kW, vaste-spoed afwind turbine ondersoek. Die afwind turbine aandrywingstelsel bestaan uit 1.9 m turbine lemme, 'n ratkas met ratverhouding van 1:3.78, 'n glip permanente magneet koppeling (S-PMC) en 'n permanente magneet sinchroon generator (PMSG). Die afwind-turbine het 'n sinchroon spoed van 600 rpm (op die hoëspoedkant van die ratkas) en is direk netwerk gekoppel deur 'n netwerkkoppelingsbeheerder (GCC). Elke komponent van die afwind turbine aandrywingstelsel was deur verskillende persone ontwerp en ontwikkel, maar die funksionaliteit van die aandrywingstelsel as 'n volledige eenheid bly onbekend. Die 2.2 kW afwind dryfbaan is gemodelleer deur gebruik te maak van wiskundige vergelykings wat dan na 'n simulasiemodel vertaal is met MATLAB/Simulink. Uit hierdie simulasiemodel is 'n oordragfunksie model van die afwind aandrywingstelsel bepaal deur 'n dinamiese stap-toets te simuleer. Die oordragfunksie van die afwind turbine stelsel is dan gebruik om 'n spoedbeheerder te ontwerp met behulp van die Internal Model Control (IMC) reëls. Die spoedbeheerder in samewerking met die GCC laat die afwind turbine toe om met die kragnetwerk te sinchroniseer en koppel sonder die behoefte aan 'n drywingsomsetter. Die dinamika van die koppeling van die gesimuleerde aandrywingstelsel na 'n kragnetwerk word ook geëvalueer met behulp van die ontwikkelde simulasiemodel. Verder, sodra die aandrywingstelsel gekoppelis, is die dinamika van die gekoppelde aandrywingstelsel getoets en geëvalueer. Afwind turbines is bekend om wringkragpulsasies teweeg te bring as gevolg van die toring skaduwee effek. Die simulasiemodel wat in hierdie tesis ontwikkel is simuleer die effekte van toringskadu en evalueer die effek op die gevolglike aandrywingstelsel. Verder ondersoek die simulasiemodel ook die dinamiese gedrag van die kragnetwerk-gekoppelde turbine tydens verskeie kragnetwerk versteurings. Die fisiese afwind turbine-aandrywingstelsel is getoets en geëvalueer op 'n meganiese toetsbank in die elektriese masjiene laboratorium. Laboratorium toetsing sluit in: . die implementering van die dinamiese stap-toets op die fisiese aandrywingstelsel, .die toets van die spoed beheerder se vermoë om die spoed van die aandrywingstelsel te bestuur en in stand te hou teen sinchroon spoed voor netwerkverbinding, . outonome netwerkverbinding met behulp van die netwerkkoppelingsbeheerder en spoed beheerder, . ondersoeke rakende die afwind aandrywingstelsel se sensitiwiteit vir wringkragpulsasies by verskillende frekwensies en, . die algehele funksionaliteit van die netwerkkoppelingsbeheerder wanneer die afwind aandrywingstelsel onderworpe is aan bogenoemde toestande. Verder het die laboratoriumtoetsresultate ooreengestem met die onderskeie gesimuleerde toetsuitslae wat gedien het as bevestiging van die akkuraatheid van die ontwikkelde simulasiemodel. Die 2.2 kW afwind turbine is opgerig by die Universiteit van Stellenbosch se Mariendahl klein windturbine toets fasiliteit. As gevolg van onvoorsiene gebeure en omstandighede kon egter geen veld-data versamel word met betrekking tot die afwind turbine. Die simulasiemodel en laboratoriumtoetse dui egter daarop dat die afwind turbine stabiel is wanneer dit netwerkgekoppel is en is nie beïnvloed deur die wringkragpulsasies wat veroorsaak word deur die toringskadu-effek nie en kan wel op die toetsveld funksioneer vir toekomstige studie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103413
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