Engine & Turbine Technology
Simulation aids design of wind turbine generators
Simulation helps the design of one of the world’s highest-efficiency permanent magnet wind turbine generators. Jon Vaquerizo and Xabier Calvo report.
La simulación contribuye al diseño de uno de los generadores de mediante turbinas eólicas con imanes permanentes de mayor eficiencia energética del mundo. Infaman Jon Vaquerizo y Xabier Calvo.
Die Simulation unterstützt die Entwicklung von einer der weltweit den höchsten Wirkungsgrad aufweisenden Dauermagnet- Windkraftanlage. Jon Vaquerizo und Xabier Calvo berichten.
W
ind power is the world’s fastest-growing energy source, with 37.5 gigawatts of installed capacity added in 2009.
Te global Wind Energy Council expects
this resource to grow by 160 per cent over the five-year period ending 2014. One rising trend is permanent magnet generators (PMGs), as they offer higher efficiency and design flexibility. Indar Electric, SL, set out to develop a 2.5MW PMG for wind power applications with the ambitious target of achieving an unprecedented 97.7 per cent level of efficiency at rated load in converting mechanical to electrical energy using a permanent magnet generator. Another goal was to increase performance and efficiency at partial loads, because wind turbines often run at partial load. Traditional build-and- test methods could not achieve these goals in a reasonable amount of time. Tus, Indar applied electromagnetic field and fluid flow simulation to facilitate the process.
generator concepts, including more-traditional double-fed induction generators (DFLG) and newer PMGs. PMGs generally offer higher efficiency at rated load and even more at partial loads, since the permanent magnets eliminate the need for rotor windings that, in turn, remove rotor ohmic losses. PMGs also eliminate the need for brushes, which reduces possible problems and maintenance needs. Te Indar design team faced several major challenges in developing its newest PMG. Achieving high efficiency was the overarching goal, but there were a number of other targets that had to be simultaneously achieved for reliable operation. Cogging torque, caused by the interaction between the rotor’s permanent magnets and the slots on the stator core, had to be reduced to 0.1 per cent of overall torque. Voltage harmonics (THD) in the output had to be kept below 0.5 per cent. For the cooling system, a demanding goal was set to maintain magnet temperature below 100°C to assure good performance of the magnets over a 20-year lifetime. Indar engineers used Maxwell low-frequency electromagnetic field simulation software from ANSYS to evaluate the effect of different geometries and magnet properties on the electromagnetic performance of the generator. Well-known basic equations were used to develop a preliminary generator design. Engineers first created a 2D and, later, a 3D model of the generator, relying primarily on manufacturing drawings to reproduce the geometry and material properties of rotor and stator laminations and coils. Te time step of the simulation was adjusted to match the rotating speed of the generator and the number of poles in the permanent magnet. Engineers simulated the performance of the proposed design under no-load, full-load and short- circuit conditions. Te results of the simulation included the
Fig. 1. Magnetic flux density level in the stator - left - identifies areas of high losses. The generated voltage - upper right- and fast Fourier transform (FFT) - lower right- results for a no-load condition are shown.
Indar electric was founded in 1940 as a manufacturer of small electric motors. In 1997, it became part of Ingeteam, a Spanish renewable energy company that currently holds about a 15 per cent global market share for wind power components. Indar produces a wide range of
voltage wave form produced by the generator, a measurement that was compared to the design requirement so that harmonic levels could be evaluated. Te voltage fast Fourier transform output capability in Maxwell provides the voltage at different frequencies, making it
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