Experimental study on the surge protection of converters in direct-driven permanent-magnetic wind turbines

Wind turbine converters may be damaged by lightning-induced surges. This paper provided an experimental study on the surge protection of converters in direct-driven permanent-magnetic wind turbines. Firstly, this paper describes the design of the experimental study and presents the obtained experimental results. Then, a discussion is presented about different earthing methods of the converter in the off-line state. Finally, the best way of earthing is found and some observations are discussed for the case when the converter is turned on.