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.

Modular Multilevel Converter Modelling, Control and Analysis under Grid Frequency Deviations

Abstract: A tool for component sizing for MMCs has been developed and tested through simulations in PLECS. The steady-state behaviour under grid frequency deviations - interesting for offshore wind farm connections - has been analysed, providing insights in MMC characteristics and further testing the proposed tool.

The role of atmospheric stability/turbulence on wakes at the Egmond aan Zee offshore wind farm

Abstract: The aim of the paper is to present results from the NREL SOWFA project that compares simulations from models of different fidelity to meteorological and turbine data from the Egmond aan Zee wind farm. Initial results illustrate that wake behavior and impacts are strongly impacted by turbulence intensity [1]. This includes both power losses from wakes and loading illustrated by the out of plane bending moment. Here we focus on understanding the relationship between turbulence and atmospheric stability and whether power losses due to wakes can effectively be characterized by measures of turbulence alone or whether atmospheric stability as a whole plays a fundamental role in wake behavior. The study defines atmospheric stability using the Monin-Obukhov length estimated based on the temperature difference between 116 and 70 m. The data subset selected using this method for the calculation of the Monin-Obukhov length indicate little diurnal or directional dependence of the stability classes but a dominance of stable classes in the spring/unstable classes in fall and of near-neutral classes at high wind speeds (Figure 2). The analysis is complicated by the need to define turbulence intensity. We can select the ratio of the standard deviation of wind speed to mean wind speed in each observation period using data from the meteorological mast, in which case a substantial amount of data must be excluded due to the presence of the wind farm. An alternative is to use data from the wind turbines which could provide a larger data set for analysis. These approaches are examined and compared to illustrate their robustness. Finally, power losses from wakes are categorized according to stability and/or turbulence in order to understand their relative importance in determining the behavior of wind turbine wakes.

Design and coordination of a capacitor and on-load tap changer system for voltage control in a wind power plant of doubly fed induction generator wind turbines

Abstract: In this paper, a novel coordination and control strategy for capacitor banks and on-load tap changer for a wind power plant is introduced. The capacitor banks are controlled in such way that the steady-state usage of the converters for reactive power injection is driven below to a maximum desired value of 0.1 pu. Additionally, the control transients because of the capacitor bank switching are minimized by using a suitable control structure. The tap changer control is coordinated with the plant control to decrease the impact of the capacitors reactive power in the line drop calculation, thus reducing the amount of tap operations and improving the accuracy of the line drop voltage estimation. The coordination of the central controller with the plant components is analysed and tested through electromagnetic transient program simulations.

Fast voltage control in wind power plants

Abstract: Growing percentages of wind power penetration translate to more demanding requirements from grid codes. Recently, voltage support at the point of connection has been introduced by several grid codes from around the world, thus, making it important to analyze this control when applied to wind power plants. Some wind power plants' turbine technologies can and should deliver voltage control with features and performance that are equivalent or improved compared to other bulk power plant technologies. With a large number of distributed controllable sources of active and reactive power, plant level control involves advanced dispatching and fast communication, two areas that have recently progressed in the application of wind plant voltage control. This paper presents a summary and analysis of the voltage control topologies, with a systematic approach to pass from overall plant performance requirements, through a process linearisation, control system design and synthesis of the plant and power system, to reach simulated and measured wind power plant performance, assessed with metrics meaningful to compliance with grid connection codes.

Methods and apparatus for servicing wind turbine components through a lower portion of a tower

Abstract: A wind turbine tower is supported on a transition piece that connects the tower to a foundation and that defines a space beneath the lower end of the tower. Electronic components positioned within a removable module in the lower portion of a wind turbine tower may be removed through a lower end of the tower for service or replacement.