34 research outputs found
Dispositif de protection d'un régulateur de tension série mettant en œuvre un transformateur de couplage à entrefer virtuel
International audienceLes régulateurs de tension série, qu'ils soient électromécaniques ou à convertisseurs statiques, constituent une solution pour améliorer la qualité de l'énergie. Cette source d'alimentation variable compense les perturbations de la tension du réseau dans lequel elle est insérée en injectant sa propre tension via un transformateur de couplage. Pour répondre à la problématique de la régulation de tension dans un contexte où l'intensité des courants de défaut peut être élevée, un régulateur de tension à électronique protégée par un entrefer virtuel est proposé. Dans ce cas, l'intégration d'une colonne de retour avec un entrefer virtuel au transformateur de couplage assure la fonction de protection du convertisseur électronique lors de défaut sur le réseau. Le concept d'entrefer virtuel repose sur la saturation locale d'un circuit magnétique dont les effets sont similaires à ceux d'un entrefer mécanique d'épaisseur variable. Cette saturation locale s'apparente donc à un by-pass magnétique qui modifie la circulation du flux dans le transformateur de couplage, selon les modes de fonctionnement
Remote laboratory of power quality
Aquest treball ha estat realitzat perquè els estudiants tinguin una millor comprensió de les pertorbacions causades pels tipus diferents d'aparells de subministrament d'energia. Es basa en l'extensió del projecte, que ja han estat fetes per antics alumnes. En l'actualitat existeixen aquestes pràctiques: un rectificador monofàsic, un rectificador de tres fases, les làmpades de baix consum d'energia, càrregues no lineals, la font d'un PC, i ara no s'ha afegit
aquestes tres plantes de pertorbació: el transformador, l'endoll, freqüència
convertidor. La major avantatge d'aquest projecte és que qualsevol persona en
qualsevol lloc i en qualsevol moment pot entrar al laboratori per Internet i
treballar amb ell. El laboratori és totalment autònom, ja que és controlada pel
PLC i està equipat amb una càmera web, que ens dóna la seva opinió del que
passa al laboratori, ja que les plantes estan equipades amb LEDs per informar
que un està en ús. Atès que el laboratori està equipat amb dispositius de
mesurament que són molt cars i no totes les escoles o institucions poden donarse
el luxe, el laboratori d'Internet és molt bona opció per il lustrar als estudiants
els processos de qualitat de l'energia
Grid Connected Doubly Fed Induction Generator Based Wind Turbine under LVRT
This project concentrates on the Low Voltage Ride Through (LVRT) capability of Doubly Fed Induction Generator (DFIG) wind turbine. The main attention in the project is, therefore, drawn to the control of the DFIG wind turbine and of its power converter and to the ability to protect itself without disconnection during grid faults. It provides also an overview on the interaction between variable speed DFIG wind turbines and the power system subjected to disturbances, such as short circuit faults. The dynamic model of DFIG wind turbine includes models for both mechanical components as well as for all electrical components, controllers and for the protection device of DFIG necessary during grid faults. The viewpoint of this project is to carry out different simulations to provide insight and understanding of the grid fault impact on both DFIG wind turbines and on the power system itself. The dynamic behavior of DFIG wind turbines during grid faults is simulated and assessed by using a transmission power system generic model developed and delivered by Transmission System Operator in the power system simulation toolbox Digsilent, Matlab/Simulink and PLECS
Power Management Strategies for a Wind Energy Source in an Isolated Microgrid and Grid Connected System
This thesis focuses on the development of power management control strategies for a direct drive permanent magnet synchronous generator (PMSG) based variable speed wind turbine (VSWT). Two modes of operation have been considered: (1) isolated/islanded mode, and (2) grid-connected mode.
In the isolated/islanded mode, the system requires additional energy sources and sinks to counterbalance the intermittent nature of the wind. Thus, battery energy storage and photovoltaic (PV) systems have been integrated with the wind turbine to form a microgrid with hybrid energy sources. For the wind/battery hybrid system, several energy management and control issues have been addressed, such as DC link voltage stability, imbalanced power flow, and constraints of the battery state of charge (SOC). To ensure the integrity of the microgrid, and to increase its flexibility, dump loads and an emergency back-up AC source (can be a diesel generator set) have been used to protect the system against the excessive power production from the wind and PV systems, as well as the intermittent nature of wind source. A coordinated control strategy is proposed for the dump loads and back up AC source.
An alternative control strategy is also proposed for a hybrid wind/battery system by eliminating the dedicated battery converter and the dump loads. To protect the battery against overcharging, an integrated control strategy is proposed. In addition, the dual vector voltage control (DVVC) is also developed to tackle the issues associated with unbalanced AC loads.
To improve the performance of a DC microgrid consisting wind, battery, and PV, a distributed control strategy using DC link voltage (DLV) based control law is developed. This strategy provides simpler structure, less frequent mode transitions, and effective coordination among different sources without relying on real-time communication.
In a grid-connected mode, this DC microgrid is connected to the grid through a single inverter at the point of common coupling (PCC). The generated wind power is only treated as a source at the DC side for the study of both unbalanced and balanced voltage sag issues at a distribution grid network.
The proposed strategy consists of: (i) a vector current control with a feed-forward of the negative-sequence voltage (VCCF) to compensate for the negative sequence currents; and (ii) a power compensation factor (PCF) control for the VCCF to maintain the balanced power flow between the system and the grid. A sliding mode control strategy has also been developed to enhance the overall system performance. Appropriate grid code has been considered in this case.
All the developed control strategies have been validated via extensive computer simulation with realistic system parameters. Furthermore, to valid developed control strategies in a realistic environment in real-time, a microgrid has been constructed using physical components: a wind turbine simulator (WTS), power electronic converters, simulated grid, sensors, real-time controllers and protection devices. All the control strategies developed in this system have been validated experimentally on this facility.
In conclusion, several power management strategies and real-time control issues have been investigated for direct drive permanent magnet synchronous generator (PMSG) based variable speed wind turbine system in an islanded and grid-connected mode. For the islanded mode, the focuses have been on microgrid control. While for the grid-connected mode, main consideration has been on the mitigation of voltage sags at the point of common coupling (PCC)
Power quality improvement utilizing photovoltaic generation connected to a weak grid
Microgrid research and development in the past
decades have been one of the most popular topics. Similarly, the
photovoltaic generation has been surging among renewable
generation in the past few years, thanks to the availability,
affordability, technology maturity of the PV panels and the PV
inverter in the general market. Unfortunately, quite often, the PV
installations are connected to weak grids and may have been
considered as the culprit of poor power quality affecting other
loads in particular sensitive loads connected to the same point of
common coupling (PCC). This paper is intended to demystify the
renewable generation, and turns the negative perception into
positive revelation of the superiority of PV generation to the power
quality improvement in a microgrid system. The main objective of
this work is to develop a control method for the PV inverter so that
the power quality at the PCC will be improved under various
disturbances. The method is to control the reactive current based
on utilizing the grid current to counteract the negative impact of
the disturbances. The proposed control method is verified in PSIM
platform. Promising results have been obtaine
Emerging Power Electronics Technologies for Sustainable Energy Conversion
This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches
Emerging Power Electronics Technologies for Sustainable Energy Conversion
This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches
Power Quality
Electrical power is becoming one of the most dominant factors in our society. Power
generation, transmission, distribution and usage are undergoing signifi cant changes
that will aff ect the electrical quality and performance needs of our 21st century industry.
One major aspect of electrical power is its quality and stability – or so called Power
Quality.
The view on Power Quality did change over the past few years. It seems that Power
Quality is becoming a more important term in the academic world dealing with electrical
power, and it is becoming more visible in all areas of commerce and industry, because
of the ever increasing industry automation using sensitive electrical equipment
on one hand and due to the dramatic change of our global electrical infrastructure on
the other.
For the past century, grid stability was maintained with a limited amount of major
generators that have a large amount of rotational inertia. And the rate of change of
phase angle is slow. Unfortunately, this does not work anymore with renewable energy
sources adding their share to the grid like wind turbines or PV modules. Although the
basic idea to use renewable energies is great and will be our path into the next century,
it comes with a curse for the power grid as power fl ow stability will suff er.
It is not only the source side that is about to change. We have also seen signifi cant
changes on the load side as well. Industry is using machines and electrical products
such as AC drives or PLCs that are sensitive to the slightest change of power quality,
and we at home use more and more electrical products with switching power supplies
or starting to plug in our electric cars to charge batt eries. In addition, many of us
have begun installing our own distributed generation systems on our rooft ops using
the latest solar panels. So we did look for a way to address this severe impact on our
distribution network. To match supply and demand, we are about to create a new, intelligent
and self-healing electric power infrastructure. The Smart Grid. The basic idea
is to maintain the necessary balance between generators and loads on a grid. In other
words, to make sure we have a good grid balance at all times. But the key question that
you should ask yourself is: Does it also improve Power Quality? Probably not!
Further on, the way how Power Quality is measured is going to be changed. Traditionally,
each country had its own Power Quality standards and defi ned its own power
quality instrument requirements. But more and more international harmonization efforts
can be seen. Such as IEC 61000-4-30, which is an excellent standard that ensures
that all compliant power quality instruments, regardless of manufacturer, will produce of measurement instruments so that they can also be used in volume applications and
even directly embedded into sensitive loads. But work still has to be done. We still use
Power Quality standards that have been writt en decades ago and don’t match today’s
technology any more, such as fl icker standards that use parameters that have been defi
ned by the behavior of 60-watt incandescent light bulbs, which are becoming extinct.
Almost all experts are in agreement - although we will see an improvement in metering
and control of the power fl ow, Power Quality will suff er. This book will give an
overview of how power quality might impact our lives today and tomorrow, introduce
new ways to monitor power quality and inform us about interesting possibilities to
mitigate power quality problems.
Regardless of any enhancements of the power grid, “Power Quality is just compatibility”
like my good old friend and teacher Alex McEachern used to say.
Power Quality will always remain an economic compromise between supply and load.
The power available on the grid must be suffi ciently clean for the loads to operate correctly,
and the loads must be suffi ciently strong to tolerate normal disturbances on the
grid
Electric Power Conversion and Micro-Grids
This edited volume is a collection of reviewed and relevant research chapters offering a comprehensive overview of recent achievements in the field of micro-grids and electric power conversion. The book comprises single chapters authored by various researchers and is edited by a group of experts in such research areas. All chapters are complete in themselves but united under a common research study topic. This publication aims at providing a thorough overview of the latest research efforts by international authors on electric power conversion, micro-grids, and their up-to-the-minute technological advances and opens new possible research paths for further novel developments