Offshore wind power converter

unlike land-based wind converter

belongs to high power medium voltage system. The design difficulty of its grid side LCL filter is reflected mainly in such aspects as limitation of switch frequency of medium voltage converter

strict limit of physical dimension and weight of filter and strict standard of current harmonics. Therefore the design of filter with traditional small power and high switch frequency low voltage converter is not appropriate any more. As for this issue

in this paper

the grid side LCL filter is designed by the method of frequency-domain model analysis with three-level neutral point clamped converter as an example. Firstly

a kind of concept of virtual voltage harmonic spectrum is proposed to provide related constrain of filter design

then the design process is simplified by the use of the concept of the relationship between energy storage and volume and

at the same time

the passive-damping technology is also used so to provide necessary damping of filter and

at the same time

maintain low loss and minimum influence of high frequency decay. Finally the performance of the filter is simulated and tested. It is shown by the test result that in case of rated inductive and capacitive output

the output harmonics complies with standard requirement

the ripple of maximum current at the converter side is less than 20% and the maximum additional loss is less than 0.5% of the p.u. The filter has reasonable design

good filtering result and low additional loss.