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Investigation of Variable DC Link Voltage Operation of a Permanent Magnet SynchronousGenerator (PMSG) based Wind Turbine with Fully Rated Converters at Steady S
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| Author(s) |
Upendra DAYARATNE, Sarath TENNAKOON, Jeremy KNIGHT, Noel SHAMMAS |
| Abstract |
The variable speed wind turbine with a multi-pole Permanent Magnet Synchronous Generator (PMSG)and Fully Rated Converter (FRC) is a popular choice for modern megawatt scale wind turbines. Twoback to back 2-level pulse width modulated (PWM) voltage source converters are typically used for theFRCs. The two converters are interconnected through the dc link capacitors. The power converters arebased on multi-chip IGBT modules. One way of increasing the inherent reliability of the FRC is toreduce the operating electrical and thermal stresses on these IGBT modules. A higher dc link voltageleads to high IGBT stresses. Higher dc link voltage is also a major contributor to cosmic ray inducedfailures. In the existing FRCs in wind turbine systems, the dc link voltage is maintained at a fixed valuewhile the modulation indices of the two converters are varied. The investigation presented in this paperand authors’ previous work shows that this fixed dc link voltage is significantly higher than the minimumdc link voltage required at the majority of the operating conditions in the maximum power point trackingrange. In the case study based on a multi-megawatt wind turbine, for generator speeds up to about 85\%of the rated speed, the dc link voltage can be lowered to match the ac system voltage by setting themodulation index of the network bridge converter to the maximum value while the modulation index ofthe generator bridge is varied to match the generator voltage. Above this speed, the generator bridgeconverter dominates at certain network conditions where its modulation index needs to be at maximumwhile network bridge modulation index is varied to match the network voltage. Simulation results showsuccessful operation of the system with minimum dc link voltages at steady state. A study on cosmicray induced failure rate calculations shows higher reliability may be achieved when the FRC is operatedwith a variable dc link voltage optimised to minimum values. |
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| Filename: | 0631-epe2011-full-01134359.pdf |
| Filesize: | 897.3 KB |
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| Type |
Members Only |
| Date |
Last modified 2012-01-26 by System |
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