Vestas

About: Vestas is a company organization based out in Aarhus, Denmark. It is known for research contribution in the topics: Turbine & Wind power. The organization has 1075 authors who have published 1519 publications receiving 23285 citations. The organization is also known as: Vestas Wind Systems & Vestas Wind Systems A/S.

Method for charging a DC link of a wind turbine power electronic converter

Abstract: The present invention relates to a method for charging a DC link of a power converter included in a wind turbine generator, the wind turbine generator comprising a generator side converter connected to an electrical generator and a grid side converter connectable, or connected, to an electrical grid through a grid circuit breaker, and a converter controller arranged to control at least the DC link, the DC link having a DC voltage level, the wind turbine generator comprising a wind turbine rotor arranged to rotate the electrical generator, wherein the method comprises rotating the wind turbine rotor whereby the electrical generator generates electrical power, rectifying the electrical power through at least one diode of the generator side converter in order to pre-charge the DC link to a DC voltage level, closing the grid circuit breaker when the DC voltage level is greater than a threshold level. The invention also relates to a wind turbine generator with a converter controller for controlling pre-charging of a DC link.

Comparative study of wire bond degradation under power and mechanical accelerated tests

Abstract: Degradation of wire bonds under accelerated power cycling tests is compared to that caused by mechanical high-frequency cycling for commercial power devices. Using micro-sectioning approach and optical microscopy it is found that the bond fracture under the mechanical cycling follows the same tendencies as that found under power cycling. Results of shear tests of the mechanically cycled bonds also agree well with the bond cracking tendencies observed by optical microscopy investigations. It is found that reduction of contact area of the wire at the bond/metallization interface due to the crack development follows the Paris-Erdogan law, which defines the degradation rate leading to wire lift-off. The results obtained on mechanical cycling in the current work also show good agreement with literature data on wire bond fracture under power cycling proving that main mechanism for wire lift-off failure is related to the mechanical stress development at the interface with metallization layer. The carried out study also creates a potential to further develop a high-frequency mechanical cycling into an alternative for reliability analysis of wire bonds. However, more studies have to be performed to compare degradation mechanisms occuring under power and mechanical accelerated tests.

Method for making a mould for a wind turbine rotor blade

Abstract: A method for making a mould for a part of a wind turbine rotor blade to be moulded in the mould, the method comprises determining whether a geometrical property of the mould is within an acceptable limit; and if the determined geometrical property is not within the acceptable limit adjusting the mould so as to bring the geometrical property to be within the acceptable limit. The mould needs not be manufactured to the final and narrow tolerances required for making wind turbine generator rotor blades, but adjustment to desired geometrical properties can be carried out according to determined geometrical properties and desired tolerances. This ensures that rotor blades can be produced with desired geometrical and aerodynamic properties and with narrow tolerances. Also, the mould can be made lighter whereby it will be less costly and easier to move and to manipulate.

Control method and apparatus

Abstract: The present disclosure relates to method and a controller for controlling a wind power generation system. The system is connected to a grid at a point of connection, and is devised to feed reactive power to the grid in order to improve grid stability. A Q-V characteristic is determined for the grid at the point of connection as well as a nose point for the Q-V characteristic. A minimum reactive current, lQmm, which is safe from the nose point, is determined, and the feeding of reactive power is controlled such that the reactive current is kept higher than the minimum reactive current. In this way it is made sure that the reactive current does not make the Q-V characteristic reverse, and thereby the stability of the system is improved.

Safety system for a wind turbine

Abstract: The invention provides a safety system for a wind turbine comprising a tower with a nacelle, and a rotor with blades and a connected drive train. The safety system comprises at least one load sensing system for providing a load signal significant for a load on the tower or rotor, and an electronic system which based on the load signal brings the wind turbine to a safe condition.