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.

A detailed comparison of system topologies for dynamic voltage restorers

Abstract: In this paper, four different system topologies for dynamic voltage restorers (DVRs) are analyzed and tested, with particular focus on the methods used to acquire the necessary energy during a voltage sag. Comparisons are made between two topologies that can be realized with a minimum amount of energy storage, with energy taken from the grid during the voltage sag, and two topologies that take energy from stored energy devices during the voltage sag. Experimental tests using a 10-kVA DVR show that the no-energy storage concept is feasible, but an improved performance can be achieved for certain voltage sags using stored energy topologies. The results of this comparison rank the no-storage topology with a passive shunt converter on the load side first, followed by the stored energy topology with a constant dc-link voltage.

Control and testing of a dynamic voltage restorer (DVR) at medium voltage level

Abstract: The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags. Implementations of the DVR have been proposed at both a low voltage (LV) level, as well as a medium voltage (MV) level; and give an opportunity to protect high power sensitive loads from voltage sags. This paper reports practical test results obtained on a medium voltage (10 kV) level using a DVR at a distribution test facility in Kyndby, Denmark. The DVR was designed to protect a 400-kVA load from a 0.5-p.u. maximum voltage sag. The reported DVR verifies the use of a combined feed-forward and feed-back technique of the controller and it obtains both good transient and steady-state responses. The effect of the DVR on the system is experimentally investigated under both faulted and nonfaulted system states, for a variety of linear and nonlinear loads. Variable duration voltage sags were created using a controllable LV breaker fed by a 630 kVA distribution transformer placed upstream of the sensitive load. The fault currents in excess of 12 kA were designed and created to obtain the required voltage sags. It is concluded the DVR works well in all operating conditions.

Overview of recent grid codes for wind power integration

Abstract: The challenge to bring down the cost of produced photovoltaic (PV) power had a major impact on the PV market and in consequence the grid operators experienced higher and higher PV power penetration. The growing share of this decentralized generation plants started to affect the grid stability and Distribution System Operators (DSOs) had to keep the safety and reliability of the network under strict rules and regulations. The aim of the paper is to realize a survey of recent Grid Codes (GC) and regulations for grid connected PV systems. The focus is on grid interface requirements, power quality concerns and Anti-Islanding (AI) issues regarding PV systems connected to low voltage (LV) and medium voltage (MV) levels of the network.

Wind turbine blade

Abstract: The invention relates to a wind turbine blade with at least one control surface and an actuator inside the main body of the wind turbine blade for moving the control surface, wherein the actuator comprises a fluidic muscle, a controller and a pump, and wherein the fluidic muscle is adapted to change in length and width when the pressure of the fluid within the fluidic muscle is varied.

Variable speed wind turbine having a matrix converter

Abstract: A variable speed wind turbine is disclosed comprising a turbine rotor that drives a doubly-fed induction generator, a matrix converter which converts variable frequency output into constant frequency output, and a control unit and a protection circuit for the matrix converter. Power is circulated in the system allowing for sensorless detection of rotor position and better output ratios of power from the system.