Andrés Feijóo

A third order model for the doubly-fed induction machine

Abstract Induction generators are generally simulated by means of a well-known model described by Brereton et al. [1] , based on the induction motor equations derived by Stanley [2] . In this model the possibility of opening the rotor circuit in order to inject a voltage source is not taken into account, although there are other models where it is dealt with [3] . This paper presents an alternative way of obtaining the mentioned model and introduces the possibility of modeling voltage sources in the rotor circuit, which can be very useful when simulating some generating schemes, such as variable speed asynchronous wind turbines.

Probabilistic Load Flow Including Wind Power Generation

In this paper, a procedure is established for calculating the load flow probability density function in an electrical power network, taking into account the presence of wind power generation. The probability density function of the power injected in the network by a wind turbine is first obtained by utilizing a quadratic approximation of its power curve. With this model, the DC power flow of a network is calculated, considering the probabilistic nature of the power injected or consumed by the generators and the loads.

Power fluctuations in an isolated wind plant

In this paper, a wind energy converter (WEC) model for the analysis of power fluctuations at an isolated wind plant is presented. The model includes the drive train dynamics, a first-order model for the asynchronous generator, and the power controller. The influence of each element is studied, and the conditions that can provoke oscillations in the power delivered by the WEC are considered. A set of measurements carried out during the setting of an isolated wind plant in the Canary Islands (Spain) is the basis for this study. In these measurements, an oscillatory behavior has been observed when wind speed was high.

Simulation of Correlated Wind Speed Data for Economic Dispatch Evaluation

The Economic Dispatch problem consists of minimizing the cost of producing the power demanded by an electrical power system, by means of the suitable dispatching of the power production between the available generators. The difficulty in predicting wind power generation means that penalty and reserve costs must be considered when it is included in the evaluation. Analyzing the output power of each wind turbine individually is not enough when evaluating these costs and the correlation between wind speed values must be considered as another input because it also has an influence. This paper introduces a new method for generating correlated wind power values and explains how to apply the method when evaluating Economic Dispatch. A case study is provided to analyze whether considering correlation in the problem has any influence or not.

A linear dynamic model for asynchronous wind turbines with mechanical fluctuations

A specific linear dynamic model for an asynchronous machine is presented. This model is based on the balanced dynamic model of the asynchronous machine, and it is developed for asynchronous wind turbines when the mechanical power (wind power) has sinusoidal fluctuations. The dynamic and the proposed linear models for real and reactive powers and voltage fluctuations analysis are considered and compared.

Synchronization of asynchronous wind turbines

In this paper, a theoretical analysis and explanation of synchronization phenomena in wind parks with asynchronous generators is presented.

On PQ Models for Asynchronous Wind Turbines

In this letter, some considerations are made regarding the representation of conventional asynchronous wind turbines (WTs) in the load flow analysis. A PQ model is presented based on the machine parameters.

Analysis of mechanical power fluctuations in asynchronous WECs

In recent years, wind energy has become an important part of electrical power generation in some countries. Some problems such as small voltage variations and flicker can be caused by wind turbines and wind farms, when wind speed variations produce mechanical power fluctuations. The consequence is that speed changes in the turbine rotor are produced, which lead to variations in their currents and voltages. The purpose of this paper is to study the relationship between fluctuations of mechanical power, rotor speed and currents as a function of their frequencies, in order to establish the models that should be used to analyse slow voltage variations and flicker problems. Simulations are carried out using a dynamic model of the induction machine and assuming sinusoidal waveforms for the fluctuations of the mechanical power.

A PQ Model for Asynchronous Machines Based on Rotor Voltage Calculation

This letter contributes toward improving the calculation of the power balance of an asynchronous machine in a power system. This is useful in power system steady-state analysis, particularly when there are wind farms in electrical power networks.

Normal-Based Model for True Power Curves of Wind Turbines

Wind turbine power curves do not consider specific weather conditions, wind shear, turbulence effects of the location where the turbine is going to be installed, or its age. A true power curve is obtained by analyzing data from an installed wind turbine over a year. Here, a model for a true power curve is proposed, considering a normal distribution for each range of wind speed data. Furthermore, a Monte Carlo-based simulation technique is proposed to reproduce data following the normal-based model. The main use of the model is to simulate data to complete lacking real data or to perform long-term assessments. The model was checked with data from two wind turbines at the Sotavento experimental wind farm in the northwest of Spain.