Object oriented simulation of hybrid renewable energy systems focused on supervisor control

EFTA 2009With eyes focused on simulation the authors review some of the main topics of Hybrid Renewable Energy Systems (HRES). Then they describe an Object Oriented model of a simple example of one of such systems, a micro-grid, oriented to designing a decentralized Supervisor Control. The model has been implemented using AnyLogic

Adaptive Sliding Mode Control for a Double Fed Induction Generator Used in an Oscillating Water Column System

Wave power conversion systems are nonlinear dynamical systems that must endure strong uncertainties. Efficiency is a key issue for these systems, and the application of robust control algorithms can improve it considerably. Wave power generation plants are typically built using variable speed generators, such as the doubly fed induction generator (DFIG). These generators, compared with fixed speed generators, are very versatile since the turbine speed may be adjusted to improve the efficiency of the whole system. Nevertheless, a suitable speed controller is required for these systems, which must be able to avoid the stalling phenomenon and track the optimal reference for the turbine. This paper proposes a sliding mode control scheme aimed at oscillating water column (OWC) generation plants using Wells turbines and DFIGs. The contributions of the paper are (1) an adaptive sliding mode control scheme that does not require calculating the bounds of the system uncertainties, (2) a Lyapunov analysis of stability for the control algorithm against system uncertainties and disturbances, and (3) a validation of the proposed control scheme through several simulation examples with the Matlab/Simulink suite. The performance results, obtained by means of simulations, for a wave power generation plant (1) evidence that this control scheme improves the power generation of the system and (2) prove that this control scheme is robust in the presence of disturbances.This research was partially funded by the Basque Government through the project ETORTEK KK-2017/00033 and by the UPV/EHU through the project PPGA18/04

Modeling smart grids as complex systems through the implementation of intelligent hubs

ICINCO 2010The electrical system is undergoing a profound change of state, which will lead to what is being called the smart grid. The necessity of a complex system approach to cope with ongoing changes is presented: combining a systemic approach based on complexity science with the classical views of electrical grids is important for an understanding the behavior of the future grid. Key issues like different layers and inter-layer devices, as well as subsystems are discussed and proposed as a base to create an agent-based system model to run simulations

Variable structure control for maximum wind power extraction

EuroPES 2009The actual wind turbines are provided with adjustable speed generators.Iike the double feed induction generator, that are capable to work in variable speed operations. One of the main advantage of adjustable speed generators is that they improve the system efficiency compared to fixed speed generators because twbine speed is adjusted as a function of wind speed to maximize output power. However this systems requires a suitable speed controller in order to track the optimal wind turbine speed reference. In this work, it is proposed a sliding mode control for variable speed wind turbines. The robustness analysis of the proposed controller under disturbances and pararneter uncertainties is provided using the Lyapunov stability theory and simulated results show that the proposed controller provides a good performance

Towards complex system design and management in the engineering domain – the smart grid challenge

This is an Author's Accepted Manuscript of an article published in “Emergence: Complexity and Organization”, 15 (2), pp. 14-22 (2013), copyright Taylor & Francis.Our world is facing a significant challenge from climate change and global warming, coupled with an increased awareness about the importance of preserving the environment. This challenge calls for us to use our resources more efficiently and develop in a more sustainable way. One important part of this move towards sustainability is a radical change in the energy sector, characterized by the introduction of new technologies providing low carbon electricity generation and the use of dynamic distribution systems such as the smart grid. This shift requires the use of new tools, especially in the modelling and simulation areas. Complexity science can help us deal with the many new challenges arising, which are mainly related to a more distributed system with a large number of dynamic, interconnected resources. New approaches to deal with these issues are presented based on two case studies

A robust position control for induction machines

ICEM 2010A robust position control for induction motors using field oriented control theory is presented. The proposed controller is based on variable structure control and provides global asymptotic position tracking in the presence of unknown parameters and load torque variations. The proposed design incorporates an improved method of flux estimation that operates on the principle of flux and current observer. The proposed observer is basically an estimator that uses a plant model and a feedback loop with measured stator voltages and currents. The stability analysis of the proposed controller under parameter uncertainties and load disturbances is provided using the Lyapunov stability theory. Finally simulated results show that the proposed controller with the proposed observer provides high-performance dynamic characteristics and that this scheme is robust with respect to plant parameter variations and external load disturbance

Using the system dynamics paradigm in teaching and learning technological university subjets

2nd International Conference on Education and New Learning TechnologiesKnowledge of Differential Equations is applied to various scientific fields such as physics, chemistry, biology and engineering and therefore often an important part in the basic subjects of mathematics in the first college courses related to those areas. The logic and common sense seems to indicate teachers use these basic skills acquired by students and employ them to curricula development in the following intensification courses, but unfortunately it is not usually the case. According to the authors, that is because instead of using a generic software to set up and solve the problems of Differential Equations that arise at different areas, what we have is a proliferation of software applied to solve special case problems. Some of these programs offer sophisticated graphical user interfaces to create complex system models, usually by putting together some library components, as if it were a puzzle, but without the need to set up the differential equations. According to the authors, this method, although valuable to solve some specific problems very quickly, is aberrant from the educational point of view, because it allows students to solve problems without knowing what they are doing or how they are doing. Worse, if a complication arises in the problem statement, for which there are no pieces in the puzzle, or execution errors occurs due to an incorrect construction, then they are not able solve the problem. Because of this, software that does not hide the equations and with the user can know at any moment what he/she is doing, from the mathematical point of view, is missing. According to the authors, any simulation program including the System Dynamics paradigm meets this condition because its GUI is very close to differential equations and the Initial Value Problem. The modelling of a system using this paradigm is simply to raise because an initial value problem associated with the system is quickly represented by the graphical user interface of the simulation program. This article presents some learning experiences focused on "problem based learning" using AnyLogic, which provides the System Dynamics paradigm to perform simulations of physical systems. The program provides a graphical environment that allows to perform animations very easily. The first on is to simulate the filling of a tank of water where the model is a first order non-linear differential equation. This case is instructive as it is very easy to raise the initial value problem and may be valid to review some concepts already forgotten by the students such as for example the derivative, integral, differential equation and initial value problem. Other simulation exercises posed to students are the control of a cart by a force, a parabolic shooting, and other mechanical, electrical and thermal examples

A Real-Time Sliding Mode Control for a Wind Energy System Based on a Doubly Fed Induction Generator

In this paper, a real time sliding mode control scheme for a variable speed wind turbine that incorporates a doubly feed induction generator is described. In this design, the so-called vector control theory is applied, in order to simplify the system electrical equations. The proposed control scheme involves a low computational cost and therefore can be implemented in real-time applications using a low cost Digital Signal Processor (DSP). The stability analysis of the proposed sliding mode controller under disturbances and parameter uncertainties is provided using the Lyapunov stability theory. A new experimental platform has been designed and constructed in order to analyze the real-time performance of the proposed controller in a real system. Finally, the experimental validation carried out in the experimental platform shows; on the one hand that the proposed controller provides high-performance dynamic characteristics, and on the other hand that this scheme is robust with respect to the uncertainties that usually appear in the real systems.The authors are very grateful to the Basque Government by the support of this work through the project S-PE12UN015 and S-PE13UN039 and to the UPV/EHU by its support through the projects GIU13/41 and UFI11/07

A real time sliding mode control for a wave energy converter based on a wells turbine

Due to the nonlinear dynamics and uncertainties usually present in wave energy conversion systems, the efficiency of these devices can be enhanced employing a robust control algorithms. Wave energy converters are constructed using electric generators of variable velocity, like double feed induction generator (DFIG) since they may improve the system efficiency to generate power when compared to fixed speed generators. The main reason is that this generators with variable speed may adapt the speed of the turbine in order to maintain the optimal flow coefficient values which improves the efficiency of the Wells turbine. However, a suitable speed controller is required in these systems first in order to avoid the stalling phenomenon and second in order to track the optimal turbine reference velocity that optimizes the power generation. In this paper a real time sliding mode control scheme for wave energy conversion systems that incorporate a Wells turbine and a DFIG is proposed. The Lyapunov stability theory is used to analyse the stability of this control scheme under parameter uncertainties and system disturbances. Next, the proposed control scheme is validated first by means of some simulation examples using the Matlab/Simulink software and second using a real-time experimental platform based on a dSPACE DS1103 control board.The authors are very grateful to the UPV/EHU by its support through the projects PPGA18/04 and UFI11/07 and to the Basque Government by its support through the project ELKARTEK KK-2017/00033. The authors also would like to thank the anonymous reviewers who have helped to improve the initial version of this paper

Adaptive variable structure control law for a variable speed wind turbine

Presentado en el 13th WSEAS International Conference on Automatic Control, Modelling and Simulation, ACMOS'11The efficiency of the wind power conversions systems can be greatly improved using an appropriate control algorithm. In this work, an adaptive robust control for a doubly feed induction generator drive for variable speed wind power generation is described. In the presented design it is applied the so called vector control theory. The control scheme uses stator flux-oriented control for the rotor side converter bridge control and grid voltage vector control for the grid side converter bridge control. The proposed robust control law is based on a sliding mode control theory, that presents a good performance under system uncertainties. The stability analysis of the proposed controller under disturbances and parameter uncertainties is provided using the Lyapunov stability theory. Finally simulated results show, on the one hand that the proposed controller provides high-performance dynamic characteristics, and on the other hand that this scheme is robust with respect to plant parameter variations and external disturbances