Wind Turbine Terminals Research Articles

Magnification of Transients at the Voltage Dips Starting and its Impacts on DFIG-based Wind Power Plants

This work shows that transients at voltage dips starting impact fault-ride-through of wind turbines. For fault-ride-through studies and manufacturer tests, it is therefore important to consider these transients and their magnification from the transmission grid through the collection grid to the wind turbines. Fault-ride-through studies in the literature do not consider the transient as a dip characteristic and employ overly-simplified models that do not consider the collection grid. This work studies in detail how the dip-starting transient changes during the propagation from the transmission grid to the wind-turbine terminals. It is also studied how this transient impacts the dynamic behaviour of the wind turbines in terms of the overvoltage on the DC-link of wind turbines based on doubly-fed induction generator (DFIG). The analyses are performed for several realistic configurations of a wind-power plant, all based on an existing installation. The results show that the magnitude of the transient is magnified when the resonant frequency of the collection grid is similar to the oscillation frequency of the transient. Moreover, the higher magnitude of the transient results in a significantly higher overvoltage on the DC-link. This work is the first in power quality literature to cover the collection and internal grid as a factor for the magnification of dip-staring transient. The main finding of this work is that the detailed models of the collection grid and the transients at the voltage dips starting must be not neglected when accessing the LVRT of wind turbines. It is strongly recommended to consider the details of the dip-starting transients and of the collection grid to assess the impact of dips on the wind turbines properly.

CFD Analysis of Auditorium using Ansys Fluent

The documented investigation in this paper examines main power quality for wind turbines and its connection with the public grid. This main goal has been to investigate most popular type of wind turbines which are grid connected using doubly-fed induction generators (DFIG) at normal operation, as well as voltage control of these wind turbines after clearing a lines short circuit in the utility grid. This paper introduces the configuration of main portions of grid connected turbines, which have an importance in the wind power plants operation. It also proposes a new compact modeling of these wind turbines, which has a feature that the expressions of most plant portions are free of any complex or details that described in other past models. Most of last models are spotted on the normal operation of single wind turbines, without consideration of gird interaction faults. The proposed control techniques are new combined and concentrated on the voltage recovery, which plays very important role in the power quality and stability of wind turbines plants which are connected with the grid. Net simulation results show that the combination of pitch control and dynamic slip control could to have power system stability efficiently, and restore the voltage to its normal condition. A simulation of wind turbine using pitch control and dynamic slip control are developed by the simulation program is called power system computer aiding design (PSCAD) and carried out the stability investigations respecting to short circuit in external power lines system. After clearing of the fault, the recovery of voltage at the terminals of wind turbine should to rebuild, then the wind power turbine should going to its normal case. Control of the pitch angle or generator slip can adjusting the aerodynamic torque and the electromagnetic torque at the turbine which can be help to recovery the voltage at the terminals of wind turbine. The results of case study simulation are proved that pitch and dynamic slip controls ar

A proposal for verification tests for the flicker measurement procedure of grid-connected wind turbines

Abstract This paper presents a set of verification tests to assist the accurate implementation of flicker measurement in wind turbines. The flicker measurement procedure is defined in the IEC 61400-21 standard, which includes the estimation of a fictitious grid in order to measure voltage fluctuations generated exclusively by the wind turbine. The large margin in the digital implementation of the fictitious grid can result in large deviations in flicker measurements between different instrument manufacturers. This work shows the need of a verification test protocol to minimize the potential divergences. Furthermore, it suggests a set of five tests aimed at guaranteeing the accurate implementation of two specific components of the fictitious grid, namely the estimation of the electrical angle of the mains frequency and the derivative of the line current measured at the wind turbine terminals. The work has been proposed to the IEC Maintenance Team TC88/MT21 for it to be included in the third edition of the standard.

An Improved Synchronous Reference Frame Controller based Dynamic Voltage Restorer for Grid Connected Wind Energy System

The production of wind generation has expanded considerably today. The main problem with wind generation system is to regulate the voltage at wind turbine terminals even under abnormal grid conditions.This is mainly as a result of consumption of non active power from the grid during grid disturbances. This paper investigates an improved Synchronous Reference Frame control; Dual Decouple Synchronous Reference Frame (DDSRF) based control for Dynamic Voltage Restorer (DVR) to upgrade the dynamic response of wind energy system. The proposed method uses DDSRF PLL for extracting clean grid voltage and phase angle even under adverse grid conditions. The proposed control scheme provides the ability for fixed speed wind generator to ride through under voltage interruptions in the grid to meet the latest grid codes. The proposed control is competent of stabilising the voltage at the wind turbine terminals under symmetrical sag/swell and asymmetrical fault conditions. simulation studies have been peformed in MATLAB/SIMULINK to manifest the effectiveness of proposed control strategy

Novel LVRT Testing Method for Wind Turbines Using Flexible VSC Technology

Wind energy is one of the fastest growing renewable energy sources. For this reason, several countries have included requirements in their grid codes to guarantee proper operation of wind turbines under stable operations of the power systems as well as under grid disturbances. This paper presents a novel methodology for grid code testing of wind turbines based on voltage source converter (VSC) technology. In particular, this paper focuses on a low voltage ride through (LVRT) test of a full size converter-based wind turbine. The investigated testing setup consists of a 4-MW wind turbine and an 8-MW back-to-back VSC system, operated as test equipment. The control algorithm of the testing device is derived in detail and validated through time-domain simulations. The risk of poorly damped resonances and possible interaction between the testing equipment and the tested object is investigated through small signal analysis. The obtained results demonstrate the flexibility of the proposed approach in controlling the voltage at the wind turbine terminals, including the ability in emulating the short-circuit impedance of the grid at the connection point.

Wind turbine converter control interaction with complex wind farm systems

This study presents wind turbine converter stability analysis of wind farms in frequency domain. The interaction between the wind turbine control system and the wind farm structure in wind farms is deeply investigated. Two wind farms (i.e. Horns Rev II and Karnice) are taken into consideration in this study. It is shown that wind farm components, such as long high-voltage alternating current cables and park transformers, can introduce significant low-frequency series resonances seen from the wind turbine terminals that can affect wind turbine control system operation and overall wind farm stability. The same wind turbine converter control strategy is evaluated in two different wind farms. It is emphasised that the grid-side converter controller should be characterised by sufficient harmonic/noise rejection and adjusted depending on wind farms to which it is connected. Various stability indices such as gain margin, vector gain margin and phase margin are used in order to emphasise the differences between the two wind farms.

Application of wavelets and Prony method for disturbance detection in fixed speed wind farms

Voltage dips and transients are the most commonly encountered power quality disturbances in wind farms. Signal parameters estimation is an important prerequisite for power quality enhancement and for improving the fault-ride capability of wind farms and consequently, the voltage stability of the whole network. This paper examines the application of advanced signal processing methodologies such as the Prony method and wavelets for disturbance detection in wind farms. Both methodologies have been effectively tested with different disturbances simulated in a dynamic power network with a large amount of wind energy and with data signals measured at wind turbine terminals.

Fault ride‐through capability test unit for wind turbines

AbstractThe GAMESA voltage ride‐through capability test unit was designed as a tool for voltage dip studies for different wind turbine (WT) configurations and to investigate specific grid code requirements. By generating a voltage dip at the WT terminals, the WT manufacturer is able to check that the equipment works according to the design specifications, fulfils the grid code requirements and can validate the simulation models. This paper presents a description of the unit, the methodology used in the field tests and the results of the study. Copyright © 2007 John Wiley & Sons, Ltd.