1,720,952 research outputs found
Transient Analysis in DC Distribution Grids
No full textThe latest developments in power electronics along with the increased generation from Renewable Energy Sources (RES), the new prosumers who both generate and consume electricity and the rapid adoption of DC loads in the household are forcing us to rethink the manner with which power is distributed and consumed. The proposal to make DC technology an integral part of the distribution network seems to have more merit. This change would lead to energy savings in power conversion and enable the creation of meshed DC grids, highly controllable and flexible networks which will be able to facilitate the more sustainable energy future towards which we strive. To build such a system, however, a different approach than the one used in AC systems is needed, due to the peculiarities of DC technology. In our research for the best possible way to protect these systems, it is imperative to constantly test the protection circuit not only as a standalone, but also incorporate it in the systems that will be built and test them together. In other words, transient analysis of the systems with the proposed protection included is an integral part in gauging the impact of the latter on the former during operation, and therefore in assessing and improving the protection for this specific application. This thesis presents such a transient analysis of various configurations of DC distribution systems. A combination of theoretical and practical methods were used to investigate the behavior of the systems' variables after the occurrence of faults and current interruption. A number of networks of varying complexity were built with detailed cable models using the EMTP/ATP software package in order to simulate a multitude of faults and assess each network's response at various positions and most crucially, the effectiveness of the protection scheme in reducing the impact of the transients after the fault. The travel speed of the transients was also investigated. At the same time, a set of measurements was conducted on a DC street lighting network to study the transient behavior of a real system. A separate model was built to resemble the measured system, in order to compare between the simulations and the measurements. The evaluation of the measurement and simulation results led to conclusions that will contribute to the creation of better, safer and more versatile DC distribution grids. The comparison showed that the models used can approach the behavior of the real system to a reasonable degree. The other simulations indicated that the transient impact is significantly smaller in locations far from the fault, but continued operation of the healthy pole cannot be guaranteed, especially after earth faults.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable Energy (ESE
Seamless Operation of a Microgrid Using BESS
No full textElectrical Engineering, Mathematics and Computer ScienceElectrical Sustainable EnergyDC systems, Energy conversion & Storag
Optimal Power Flow and Pricing Mechanism for Bipolar DC Distribution Grids
No full textElectrical Engineering, Mathematics and Computer ScienceElectrical Sustainable EnergyDC Systems, Energy Conversion & Storag
Load Side Detection of Series Arcs in DC Microgrids by Simulation and Experimental Validation
No full textWith increasing scale of usage for renewable energy resource, DC micro-grids system becomes more and more popular for the application of different kinds of power electronics in DC. However DC arc fault introduces major safety concerns due to the randomness and instability, especially absence of zero current crossing, which makes it is hard to be detected and eliminated. In this thesis, a novel proposed series dc arc detection methods were validated both in theoretical simulation by MATLAB and in real-time experiments by creating real arcing in the constructed equivalent DC system. By changing the parameters and type of both the circuit and the setting of detection method, the arc detection performs with sensitivity, selectivity, speed and reliability harvested. Additionally, the research and practical tests have also been conducted to study the characteristics of series dc arc, which contributes to the determination of the appropriate setting value for the arc detection algorithm.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable Energy (ESE
Data Communications in an In-Home Smart Grid: Communicating with the Tesla Powerwall
No full textMore insight and control is warranted over an in-home energy management system, consisting in our case mainly of a Tesla Powerwall and a SolarEdge Inverter, in order to allow for further research and development on the possibilities within the field. Not much is known yet on the Tesla Powerwall and its communication, as they aren’t widely available yet and documentation is lacking. In order to achieve this insight, the communicated signals within the system have to read, analysed and used for possible charging commands. Software has been written on a single board computer, which establishes a connection, logs the messages send, displays the retrieved information on a locally hosted webpage and computes a charging command based on the retrieved information and entered user preferences. Even though the analysis of the logged communication signals was lacking due to the Powerwall not initializing, the achieved results should offer a good foundation for further research on the Tesla Powerwall and in-home energy management systems.Electrical Engineering, Mathematics and Computer ScienceDC systems, Energy conversion & Storag
Seamless transitions of multiple micro-grids between the backbone interconnected and the islanded operational modes
No full textThe traditional power system has been undergoing fundamental changes during the latest years. The developments in the field of renewable energy sources, as well as in the power electronics industry, acted as drivers aiding the establishment of micro-grids. Nowadays, power production is becoming more and more decentralized, therefore loads and consumers are powered via local generation avoiding the losses resulting from the transmission system. However, there is still a lot of research needed in the field of micro-grids, before they are mature enough to penetrate the conventional system at a large extent. This thesis aims to contribute to the further development of the field of micro-grids. The thesis focuses on a grid comprised of various micro-grids working in parallel. The micro-grids are interconnected through a low voltage backbone. Each micro-grid can operate either in islanded mode or connected to the backbone and working in parallel with other micro-grids. The main restriction that has to be respected is the lack of ICT equipment. Only local measurements are allowed and each of the interconnected micro-grids cannot acquire information for the rest of the micro-grids. Thus, the frequency of the system is the only communication signal and the main control variable. The frequency closely reflects the state of the system. The main component of each micro-grid is the converter of the battery energy storage system. Apart from that, each micro-grid consists of a PV system and a load, as well as the connection to the backbone. The key aspect is the lack of connection to the main grid. The backbone interconnected system can be perceived to be working in stand-alone mode. Within this regime, the question arises as to how to achieve seamless transitions of such a micro-grid between the islanded and the backbone interconnected operational modes. The literature shows many examples of such transitions of a micro-grid and the main grid. This thesis addresses the seamless mode switching issue in an extended grid comprised of parallel micro-grids and under the absence of a main conventional grid. The main aim of this thesis was to develop adequate controllers which would ensure seamless transitions of the previously described micro-grid between the islanded and the backbone interconnected operation. Nevertheless, in order to implement and test the efficiency of the controllers, the development of a base-model regulating the operation of the micro-grid both in islanded and in backbone interconnected mode was necessary. The respective controllers were developed in the PowerFactory simulation software and their efficiency was tested under different operational conditions, especially under extreme cases. The results were evaluated and conclusions were finally drawn.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable Energ
Power Balance Control of DC Microgrids
No full textControl techniques for DC microgrid.Electical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc
Optimal Usage of Multiple Energy Carriers in Residential Systems: Unit Scheduling and Power Control
No full textThe world’s increasing energy demand and growing environmental concerns have motivated scientists to develop new technologies and methods to make better use of the remaining resources of our planet. The main objective of this dissertation is to develop a scheduling and control tool at the district level for small-scale systems with multiple energy carriers and to apply exergy-related concepts for the optimization of these systems. The tool is based on the energy hub approach and provides insights and techniques that can be used to evaluate new district energy scenarios. The topics that are presented include the multicarrier unit commitment framework, the multi-carrier exergy hub approach, a hierarchical multi-carrier control architecture, a comparison of multi-carrier power applications and the implementation of a multi-carrier energy management system in a real infrastructure.Electrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc
The Increasing Importance of Small and Medium Scale Renewable Energy Systems: DENLab: Renewable Energy Laboratory at TU Delft
No full textElectrical Engineering, Mathematics and Computer Scienc
Optimization and Energy Management of a Microgrid Based on Frequency Communications
No full textIn recent years, a transition towards a more sustainable future has started and it is imperative that this trend continues. An increasing energy demand from the continuously growing population, together with the increment of greenhouse gasses (GHG) emissions and the depletion of fossil fuels have motivated the penetration of renewable energy systems (RESs) in different areas and scales. As a consequence, the energy sector is facing a transition from a centralized network, composed of large and controllable power plants, to a decentralized grid based on RESs. Within this framework, microgrids (MGs) provide a key solution to integrate RESs, controllable energy resources, flexible loads and storage systems either in a grid-connected or an islanded mode. Optimal energy management is crucial to develop strategies to improve the efficiency and reliability ofMGs, as well as newcommunication networks to support optimal and reliable operation. This study proposes an energy management system (EMS) whose main objective is to optimally operate a microgrid (MG) using frequency as the only communication signal. The developed model considers renewable energy sources (RESs) such as photovoltaic (PV) panels and wind turbines, a micro-generator, a battery energy storage system (BESS) and both critical and controllable loads. In a conventional grid with a control system based on frequency communications, each element of the grid has a droop curve and the frequency reflects the generation - load balance as a result of a compromise between each other. However, in the inertia-less grid proposed in this thesis the EMS controls the BESS and solves the optimization problem, which determines the optimal frequency of the system. The rest of the system components react according to the optimal frequency by following their specific frequencypower response curves. In thisway, an optimal planning and operation of theMGis sought in order to minimize operational costs and consequently increase the use of RESs, reduce GHG emissions, perform a smart charge of the BESS and optimally operate the diesel generator. A demand-side management (DSM) mechanism is introduced in order to manage controllable loads via load-shedding to match availability of RESs. To further adjust generation to load demand, RESs curtailment or supply-side management (SSM) is implemented through the application of a version of an available standard that ensures grid security when connecting RES generators to the grid. The performance of the proposed EMS will be validated through simulation results for different scenarios using real numerical data from an existing microgrid, comparing the results against the traditional control system.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable EnergyDC systems, Energy conversion & Storag
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