Abstract
Permanent magnet Vernier (PM-V) machines, at low power levels (few kWs), have shown a great potential to improve the torque density of existing direct-drive PM machines without much compromising on efficiency or making the machine structure more complicated. An improved torque density is very desirable for offshore wind power applications where the size of the direct-drive machine is an increasing concern. However, the relatively poor power factors of the PM-V machines will increase the power converter rating and hence cost. The objective of this paper is to review the benefits and challenges of PM-V machines for direct-drive offshore wind power applications. The review has been presented considering the system-level (direct-drive generator + converter) performance comparison between the surface-mounted permanent magnet Vernier (SPM-V) machines and the conventional SPM machines. It includes the indepth discussion on the challenges facing the PM-V machines when they are scaled up for multi-MW offshore wind power application. Other PM-V topologies discussed in literature have also been reviewed to asses their suitability for offshore wind power application.
Highlights
The offshore wind market is growing rapidly with almost 24% average year-on-year growth since 2013 [1]
This paper aims to summarize the work published in these papers providing useful insight into the benefits and challenges of Vernier machines for direct-drive multi-MW offshore wind power applications
The scaling study performed over a wide range of power ratings has proven that the Permanent magnet Vernier (PM-V) machines can still achieve a torque density 60-80% higher than that of the conventional surface-mounted PM (SPM) machines
Summary
The offshore wind market is growing rapidly with almost 24% average year-on-year growth since 2013 [1]. Vernier machines, based on the same principle as magnetically geared machines [16], have become very popular mainly due to their high torque density combined with simple machine structure These machines have a relatively low power factor compared to conventional SPM machines. This paper aims to summarize the work published in these papers providing useful insight into the benefits and challenges of Vernier machines for direct-drive multi-MW offshore wind power applications. This involves some indepth discussions about the following points:. Impact of scaling on the system-level (direct drive generator + power converter) performance of Vernier machines in comparison with the conventional SPM machines
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