Dynamic modelling of wind turbine and power system for fault ride-through analysis

This paper presents a Simulink model of a wind power system for the holistic analysis of wind turbine and power grid during grid faults, aiming to investigate wind turbine Fault Ride-Through performance. The model comprises a highly detailed dynamic model of a 2MW wind turbine and a generic electrical network model. The simulation result shows the behaviour of both wind turbine and power grid when grid faults occurs. The impact that a grid fault has on wind turbine components and grid transients is illustrated and discussed

Control based power smoothing for aggregated vertical axis wind turbines

Recently there has been renewed interest in the potential of vertical axis wind turbines (VAWTs), particularly, at very large scale of 10 MW or above owing to their structural simplicity. A significant disadvantage for many types of VAWTs is that the generated power is inherently periodic in nature. This power quality issue is exacerbated as the turbines increase in size and are aggregated requiring the transmission system to withstand large transients. These periodic perturbations in power can be smoothed out by permitting the rotor speed to vary; however, operation in this manner results in a poor capacity factor. A new approach to smoothing the power fluctuations from aggregated VAWTs is proposed, whereby a controller for a small group of turbines is used to adjust the relative phase of the periodic power output from individual machines while maintaining the overall performance of the turbines in a group. Simulation of this control scheme demonstrates that the fluctuations in the aggregated power can be significantly reduced without affecting the mean aggregated power output. The control strategy has been tested by simulation for a range of farm configurations at various wind speeds. The results indicate that the proposed control scheme becomes more effective for increased number of turbines

Model predictive control of a variable-speed pitch-regulated wind turbine

The Model Predictive Controller is designed for a 5MW variable-speed pitch-regulated wind turbine for three operating points – below rated wind speed, just above rated wind speed, and above rated wind speed. At each operating point, the controllers are designed based on two different linear models of the same wind turbine to investigate the impact of using different control design models (i.e. the model used for designing a model-based controller) on the control performance

An investigation of control strategies on gearbox damage

The impact of control on structural elements such as tower and blades have been thoroughly researched and the validity of analysis methods based on aeroelastic simulations is widely accepted. The implications on gearbox wear for various control strategies is less studied. Using RomaxDesigner for gearbox analysis, MLS and Romax have carried out an investigation where the impact of different control strategies on wear is assessed. The best measures accounting for gearbox damage are described and the different control strategies and their impact on the gearbox are detailed

Issues in the design of switched linear systems : a benchmark study

In this paper we present a tutorial overview of some of the issues that arise in the design of switched linear control systems. Particular emphasis is given to issues relating to stability and control system realisation. A benchmark regulation problem is then presented. This problem is most naturally solved by means of a switched control design. The challenge to the community is to design a control system that meets the required performance specifications and permits the application of rigorous analysis techniques. A simple design solution is presented and the limitations of currently available analysis techniques are illustrated with reference to this example

Influence of lift to drag ratio on optimal aerodynamic performance of straight blade vertical axis wind turbines

This paper defines an effective lift to drag for a vertical axis wind turbine design based on averaged torque per cycle. This metric is used to characterise the relationship between overall optimum aerodynamic performance and design parameters. A double multiple streamtube aerodynamic prediction model is employed to demonstrate the effect of lift to drag ratio on optimal power performance for the H-rotor and the V-rotor concept VAWT. A further study looks at the effect of coning angle for the V-rotor

Enhanced power system stability by coordinated PSS design [Correction]

A step-by-step coordinated design procedure for PSSs and AVRs in a strongly-coupled system is described. It is shown that it is possible to separate the design of individual PSSs and to separate the design of individual AVRs. Thereby, the designs of AVR and PSS devices at a given machine can be coordinated to achieve near optimal overall power system stability performance, including oscillation stability performance and transient stability performance. The proposed coordinated PSS/AVR design procedure is established within a frequency domain framework and serves as a most useful small-signal complement to established large-signal transient simulation studies

Derivative observations in Gaussian Process models of dynamic systems

Gaussian processes provide an approach to nonparametric modelling which allows a straightforward combination of function and derivative observations in an empirical model. This is of particular importance in identification of nonlinear dynamic systems from experimental data. 1)It allows us to combine derivative information, and associated uncertainty with normal function observations into the learning and inference process. This derivative information can be in the form of priors specified by an expert or identified from perturbation data close to equilibrium. 2) It allows a seamless fusion of multiple local linear models in a consistent manner, inferring consistent models and ensuring that integrability constraints are met. 3) It improves dramatically the computational efficiency of Gaussian process models for dynamic system identification, by summarising large quantities of near-equilibrium data by a handful of linearisations, reducing the training size - traditionally a problem for Gaussian process models

Control of DFIG wind turbines in offshore networks during large transients

Control flexibility and fault ride-through capability of offshore wind farms and their electrical collectors array have been studied in this paper. The research is focused on the implementation of different control techniques for large offshore wind farms and also for variable wind turbines. The third harmonic injection technique is added to improve the modulation signal, which is fitted into the PWM system. Improvements in the acquisition and process of the reference signal for the inner and outer current controllers have shown significantly power peaks’ reduction during large transients. Also, fault current reduction and reduction of the recovery time have been observed. The control system also improves considerably dc voltage performance in the HVDC link. Overall, results have shown significant improvements in the active and reactive power transmission for the ac star layout in the collector