625 research outputs found
Study and evaluation of distributed power electronic converters in photovoltaic generation applications
This research project has proposed a new modulation technique called “Local Carrier Pulse
Width Modulation” (LC-PWM) for MMCs with different cell voltages, taking into account the
measured cell voltages to generate switching sequences with more accurate timing. It also adapts
the modulator sampling period to improve the transitions from level to level, an important issue to
reduce noise at the internal circulating currents. As a result, the new modulation LC-PWM
technique reduces the output distortion in a wider range of voltage situations. Furthermore, it
effectively eliminates unnecessary AC components of circulating currents, resulting in lower
power losses and higher MMC efficiency.Departamento de TecnologĂa ElectrĂłnicaDoctorado en IngenierĂa Industria
CONTROLLERS AND METHODS FOR DIFFERENT ELECTRICAL MEASUREMENTS IN SYNCHRONIZATION OF RENEWABLE ENERGY SOURCES FOR GRID CONNECTIVITY: A REVIEW
In this paper, different controllers used in synchronization of renewable energy sources are studied. A study regarding the use of artificial intelligence in synchronization of grid connected power converters, efficient method for phase angle detection, frequency variation detection and good performance during voltage depression etc  carried out here. Importance of hybrid controllers over conventional controllers is also presented. Possibility of Z source T type inverter as an alternate solution to DC-DC converter is explored based on existing works
Control and grid integration of MW-range wind and solar energy conversion systems
Solar-based energy generation has increased by more than ten times over the same period. In total, worldwide electrical energy consumption increased by approximately 6340 TWh from 2003 to 2013. To meet the challenges created by intermittent energy generation sources, grid operators have increasingly demanded more stringent technical requirements for the connection and operation of grid-connected intermittent energy systems, for instance concerning fault ride through capability, voltage and frequency support, and inertia emulation. Ongoing developments include new or improved high-voltage converters, power converters with higher power density, control systems to provide ride-through capability, implementation of redundancy schemes to provide more reliable generation systems, and the use of high-voltage direct current (HVdc) links for the connection of large off-shore intermittent energy systems
Developing A Medium-Voltage Three-Phase Current Compensator Using Modular Switching Positions
The objective of this thesis is to present the context, application, theory, design, construction, and testing of a proposed solution to unbalanced current loading on three-phase four-wire systems. This solution, known as the Medium-Voltage Unbalanced Current Static Compensator or MV-UCSC, is designed to recirculate currents between the three phases of adistribution system. Through this redistribution of the currents negative- and zero-sequence current components are eliminated and a balanced load is seen upstream from the point of installation. The MV-UCSC as it operates in the distribution system is presented followed by its effect on traditional compensation equipment. The construction of the MV-UCSC as well as 13.8 kV simulations are then shown. Development of the switching positions required by the MVUCSC is then given followed by a variation on this switching position with the intent to reduce part count. Finally, the testing the 13.8 kV three-phase four-wire, neutral-point-clamped, elevenlevel, flying-capacitor-based MV-UCSC connected directly to the grid is presented
Multilevel Converter Topologies for Utility Scale Solar Photovoltaic Power Systems
Renewable energy technologies have been growing in their installed capacity
rapidly over the past few years. This growth in solar, wind and other technologies is
fueled by state incentives, renewable energy mandates, increased fossil fuel prices and
environmental consciousness. Utility scale systems form a substantial portion of
electricity capacity addition in modern times. This sets the stage for research activity to
explore new efficient, compact and alternative power electronic topologies to integrate
sources like photovoltaics (PV) to the utility grid, some of which are multilevel
topologies.
Multilevel topologies allow for use of lower voltage semiconductor devices than
two-level converters. They also produce lower distortion output voltage waveforms. This
dissertation proposes a cascaded multilevel converter with medium frequency AC link
which reduces the size of DC bus capacitor and also eliminates power imbalance
between the three phases. A control strategy which modulates the output voltage
magnitude and phase angle of the inverter cells is proposed. This improves differential
power processing amongst cells while keeping the voltage and current ratings of the
devices low.
A battery energy storage system for the multilevel PV converter has also been
proposed. Renewable technologies such as PV and wind suffer from varying degrees of
intermittency, depending on the geographical location. With increased installation of
these sources, management of intermittency is critical to the stability of the grid. The
proposed battery system is rated at 10% of the plant it is designed to support. Energy is stored and extracted by means of a bidirectional DC-DC converter connected to the PV DC bus. Different battery chemistries available for this application are also discussed.
In this dissertation, the analyses of common mode voltages and currents in various PV topologies are detailed. The grid integration of PV power employs a combination of pulse width modulation (PWM) DC-DC converters and inverters. Due to their fast switching nature a common mode voltage is generated with respect to the ground, inducing a circulating current through the ground capacitance. Common mode voltages lead to increased voltage stress, electromagnetic interference and malfunctioning of ground fault protection systems. Common mode voltages and currents present in high and low power PV systems are analyzed and mitigation strategies such as common mode filter and transformer shielding are proposed to minimize them
Five-Level Flying Capacitor Converter used as a Static Compensator for Current Unbalances in Three-Phase Distribution Systems
This thesis presents and evaluates a solution for unbalanced current loading in three-phase distribution systems. The proposed solution uses the flying capacitor multilevel converter as its main topology for an application known as Unbalanced Current Static Compensator. The fundamental theory, controller design and prototype construction will be presented along with the experimental results. The Unbalanced Current Static Compensator main objective is the balancing of the up-stream currents from the installation point to eliminate the negative- and zero-sequence currents originated by unbalanced single-phase loads.
Three separate single-phase flying capacitor converters are controlled independently using a d-q rotating reference frame algorithm to allow easier compensation of reactive power. Simulations of the system were developed in MATLAB/SIMULINK™ in order to validate the design parameters; then, testing of the UCSC prototype was performed to confirm the control algorithm functionality. Finally, experimental result are presented and analyzed
Ancillary Services in Hybrid AC/DC Low Voltage Distribution Networks
In the last decade, distribution systems are experiencing a drastic transformation
with the advent of new technologies. In fact, distribution networks are no longer passive
systems, considering the current integration rates of new agents such as distributed generation,
electrical vehicles and energy storage, which are greatly influencing the way these systems are
operated. In addition, the intrinsic DC nature of these components, interfaced to the AC system
through power electronics converters, is unlocking the possibility for new distribution topologies
based on AC/DC networks. This paper analyzes the evolution of AC distribution systems,
the advantages of AC/DC hybrid arrangements and the active role that the new distributed agents
may play in the upcoming decarbonized paradigm by providing different ancillary services.Ministerio de EconomĂa y Competitividad ENE2017-84813-RUniĂłn Europea (Programa Horizonte 2020) 76409
ELEVEN LEVEL INVERTER DESIGN WITH DVR FOR DISTRIBUTION ENERGY SYSTEM
 In this paper with flexible AC transmission system capability is implemented. The proposed inverter is placed between the wind turbine and the grid, same as a regular WEI, and is able to regulate active and reactive power transferred to the grid. This inverter is equipped with dynamic voltage restorer option in order to control the power factor of the local feeder lines. The goal of this project is to introduce new ways to increase the penetration of renewable energy systems into the distribution systems. This will encourage the utilities and customers to act not only as a consumer, but also as a supplier of energy.Â
Integration of renewable energy resources into the distribution network : a review on required power quality
Power quality is the critical element of modern power system network where more and more distributed energy resources (DER) can be found. Distributed generation, generates electricity from many small DER particularly from renewable sources. Distributed generator (DG) within the network from renewable energy resources (RER) like solar and wind, bring significant challenges to maintain acceptable power quality (PQ) at the consumer end. This paper investigates PQ issues associated with RER. It reviews existing PQ standards for distribution network (DN) and also summarized the experiences of several Distributed Network Service Provider (DNSP) while integrating DGs into the grid. It was found that few PQ parameter ranges varies in different standards due to lack of harmonization and that may hinder to accept bulk renewable energy into the grid
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