Design and evaluation of medium speed geared direct grid connected wind generator drive train with specific focus on slip permanent magnet coupling

Van Wyk, Petrus Johannes Jacobus (2015-12)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: In this study an alternative drive train topology for the slip-synchronous permanent magnet generator (SS-PMG) is proposed. The SS-PMG was first proposed in 2010 and is a direct drive, direct grid-connected wind generator, consisting of two sections, a slip permanent magnet coupling (S-PMC) and a permanent magnet synchronous generator (PMSG). These two machines are mechanically connected via a common PM rotor. The PMSG section is directly grid-connected, but this is only possible due to the damping effects of the S-PMC on wind transients. Since the SS-PMG is a direct drive generator, it operates at turbine speed. In this thesis it is proposed that the SS-PMG be split into two separate machines: a free standing S-PMC and a free standing PMSG. It is also proposed that a gearbox be introduced, to allow greater flexibility in speed selection, which allows the S-PMC and PMSG to operate in the medium speed range (100 - 600 r/min) or at even higher speeds for small scale turbines. All the components of the drive train are investigated. The turbine blade characteristics are combined with the wind speed data of a proposed wind site to determine the drive train operating speed, as well as the S-PMC and PMSG power ratings. The gearbox is investigated and laboratory tested to determine its operating efficiency. A free standing S-PMC is not widely known in literature, and thus the S-PMC is investigated in great detail. The S-PMC is simulated and design optimised using finite element (FE) modelling, and a 2.2 kW prototype of the S-PMC is built and laboratory tested. The PMSG is also simulated and design optimised using FE modelling, but a prototype was not built. Finally the efficiency of the entire drive train is evaluated, by combining measured, simulated and calculated data of the various drive train components. The gearbox achieves a high efficiency of up to 96% at rated loads. The S-PMC performs better than expected, with the prototype producing 20% more output torque than the S-PMC simulations at rated slip, due to superior thermal characteristics of the open design. The proposed FE analysis method for the S-PMC proves to accurately model the machine. The simulated PMSG achieves a 93% efficiency at rated conditions and appears to be feasible for direct grid-connected use. The entire drive train shows to have a good efficiency of above 80% for most of its operating range.

AFRIKAANSE OPSOMMING: In hierdie studie word ’n alternatiewe aandrywingstelsel topologie vir die glipsinchroon permanente magneet generator (SS-PMG) voorgestel. Die SS-PMG is die eerste keer voorgestel in 2010 en is ’n direk aangedrewe, direk netwerk gekoppelde wind generator, wat bestaan uit twee gedeeltes, ’n glip permanente magneet koppeling (S-PMC) en ’n permanente magneet sinchroon generator (PMSG). Hierdie twee masjiene word meganies verbind deur ’n gemeenskaplike PM rotor. Die PMSG is direk netwerk gekoppel, maar dit is slegs moontlik weens die dempingseffek van die S-PMC op wind oorgangsverskynsels. Aangesien die SS-PMG ’n direk aangedrewe generator is, hardloop dit teen turbine spoed. In hierdie tesis word dit voorgestel dat die SS-PMG verdeel word in twee afsonderlike masjiene: ’n vrystaande S-PMC en ’n vrystaande PMSG. Dit word ook voorgestel dat ’n ratkas bygevoeg word, om meer vryheid te gee met spoed seleksie, wat die S-PMC en PMSG toelaat om te werk in die medium spoed reeks (100-600 r/min), of moontlik teen selfs ho¨er snelhede vir kleinskaalse turbines. Al die komponente van die aandryfstelsel word ondersoek. Die turbine lem eienskappe word gekombineer met wind spoed data van ’n voorgestelde wind plaas om die aandryfstelsel spoed te bepaal, sowel as om die S-PMC en PMSG drywing groottes te bepaal. Die ratkas word ondersoek en in die laboratorium getoets om sy bedryfseffektiwiteit te bepaal. ’n Vrystaande S-PMC is nie wyd bekend in die literatuur nie, en dus word die S-PMC in groot detail ondersoek. Die S-PMC word gesimuleer en ontwerp met behulp van eindige element (FE) modellering, en ’n 2.2 kW prototipe van die S-PMC word gebou en in die laboratorium getoets. Die PMSG word ook gesimuleer en ontwerp met behulp van FE modellering, maar ’n prototipe was nie gebou. Ten slotte word die effektiwiteit van die hele aandryfstelsel ge¨evalueer met ’n kombinasie van gemete, gesimuleerde en berekende data van die verskillende aandryfstelsel komponente. Die ratkas bereik ’n ho¨e effektiwiteit van tot 96% by kenlas. Die S-PMC presteer beter as te verwagte, met die prototipe wat teen kenglip 20% meer wringkrag uitsit as die S-PMC simulasies, te danke aan beter termiese eienskappe weens die oop ontwerp. Dit word bevind dat die voorgestelde FE analise metode vir die S-PMC die masjien akkuraat modelleer. Die gesimuleerde PMSG bereik ’n effektiwiteit van 93% teen kenwaardes en blyk om bruikbaar te wees vir ’n direk netwerk gekoppelde toepassing. Dit word bevind dat die hele aandryfstelsel ’n goeie effektiwiteit van bo 80% het vir die meerderheid van sy reeks bedryfspunte.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/97889
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