1,720,952 research outputs found
Erratum to: Energy management system with pv power forecast to optimally charge evs at the workplace (IEEE Transactions on Industrial Informatics (2018) 14:1 (311-320) DOI: 10.1109/TII.2016.2634624)
No full textIn [1], the name of one co-author, Germán Morales-Espana, was rendered incorrectly as Germán Morales-Espana Mouli. The correct byline is shown above. We sincerely regret the error.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & StorageAlgorithmic
Developing smart charging strategies for large-scale integration of photovoltaics and electric vehicles
No full textAs the state of the environment deteriorates due to the large energy consumption in the world, the importance of green technologies like photovoltaic (PV) generators and electric vehicles (EVs) increases. Both are making their appearance as common technologies in the modern life. However, separately these technologies can have bad influences on distribution networks. Fortunately, PV and EV have a natural synergy: when the PV energy is stored directly in the EV batteries, the currents to and from the grid can be kept within limits. To enable this synergy, the EVs should be charged during the peak hours of the sun and the EVs should be connected directly to the PV panels. This thesis presents different strategies of charging EVs at an office with PV arrays, in order to integrate large amounts of PV and EV without causing any grid violations. A general framework for the different strategies is developed, containing an aggregator, the EV charging stations and a grid monitoring system. Three different ways of mitigating grid violations when they would appear are defined, and each of these start charging either at maximum charging power or average charging power. The strategies make real-time choices based on the state of the EVs and the grid. In this way, the EVs will be fully charged upon departure (typical constant current/constant voltage mode charging for lithium-ion batteries included) while keeping the transformer power, the line currents and the node voltages within the limits. The first charging strategy shares the violation mitigation among all EVs: the charging power of all available EVs are adjusted in low extend in order to create more balance in the power flows. The second charging strategy makes use of location-dependent violation mitigation: only the EVs at the location with the most impact are adjusted. In this way, the violation will be mitigated as effective as possible, so by adjusting the least amount of aggregated charging power. The third charging strategy ranks the EVs based in their energy demand, remaining connection time and their location. Then the most flexible EVs are adjusted as much as they can in order to mitigate grid violations. In this case there is not a large fleet in which all EVs have to adjust in low extend, but there are a few EV that have to adjust in large extend. In this way, the least EVs are affected by the violation mitigation. The results show that charging at average charging power has many more benefits than charging at maximum charging power, especially in case of a lot of solar power generation. Besides, it is found that fair sharing of grid violation mitigation results in the least losses because of the flat current profiles they cause. Unfair sharing results in large current peaks, more losses and current violations besides the voltage violations. Adjusting less EVs in larger extend is more effective than adjusting many EVs in small extend, because it takes the EV parameters into account: in this way the least flexible EVs are spared and will not cause any problems at the end of the day.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable EnergyDC systems, Energy conversion & Storag
Optimal topology for a three port PV-EV-Grid power converter
No full textThis thesis focuses on the search for the optimal converter which can be used as a single solution for both EV charging and PV energy production. The three port converter must be able to charge the battery from both the grid and solar power, and inject current to the grid from both the solar array and the EV battery, allowing V2X operation. Maximal efficiency is wanted to reduce heating and maximize profit while keeping the overall volume low, making the product appropriate for both residential and industrial applications.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable EnergyDC systems, Energy conversion & Storag
Charging electric vehicles from solar energy: Power converter, charging algorithm and system design
No full textElectric vehicles are only sustainable if the electricity used to charge them comes from renewable sources and not from fossil fuel based power plants. The goal of this PhD thesis is to develop a highly efficient, V2G-enabled smart charging system for electric vehicles at workplaces, that is powered by solar energy. The thesis focusses on three research elements – power converter, charging algorithms and system design. A 10kW EV charger has been developed that enables the direct DC charging of EV from PV without converting to AC. The charger is bidirectional, so energy from the EV battery can also be fed to the grid for vehicle to grid (V2G). The charger can realize four different power flows: PV → EV, EV → Grid, Grid → EV, PV → Grid. The 10kW modules are modularly built and can be operated without solar input as a bidirectional EV charger as well. Further, several DC charger modules can be operated paralleled for fast charging up to 150kW. The charger is based on silicon carbide and quasi-resonant technology which results in high efficiency (>96%) for both full load and partial load. The integrated EV-PV solution has a lower component count, three times higher power density and lower cost than using separate EV charger and PV inverter exchanging power over AC. The charger is compatible with the CHAdeMO and CCS/Combo charging standard and is designed for implementing smart charging. New smart charging algorithms developed in the project integrate several applications together: PV forecast, EV user preferences, multiplexing of EVs, V2G demand, energy prices, regulation prices and distribution network constraints. For two case studies simulated for Netherlands and Texas, the proposed algorithms reduced the net costs by up to 427% and 651% when compared to average rate charging, respectively.DC systems, Energy conversion & Storag
Comparison of system architecture and converter topology for a solar powered electric vehicle charging station
No full textAccepted Author ManuscriptOld - EWI-ESE-DC&S DC systems & StoragePhotovoltaic Materials and Device
Increasing the Braking Energy Recuperation in Electric Transportation Grids Without Storage
No full textWhen the braking energy in electric transportation grids is not met by another vehicle's demand, it is either harvested by storage systems or wasted in braking resistors. This paper looks at three methods for increasing the amount of harvested braking energy without the use of expensive storage systems: decreasing the substation voltage, decreasing the catenary/rail resistance, and adding smart grid loads such as EV chargers. Compared to the baseline scenario of a presented case study, the first method allowed the recuperation of all the braking energy yet increased the line transmission losses. The second method presented a better performance in both types of losses (23 %), while the third method offered a 66 % reduction in losses in addition to offering more utilities from the same infrastructure. The final paper will go into further detail with a full-day simulation.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
A Traction Substation State Estimator for Integrating Smart Loads in Transportation Grids Without the Need for Additional Sensors
No full textPublic electric transport grids tend to be oversized and underutilized. Therefore, they can become sustainable and multi-functional backbones to the city AC grid by integrating smart grid elements into their infrastructures. However, integrating smart grid loads and renewables requires a large array of wirelessly communicating sensors across the traction substations, the smart grid components, and each vehicle of the transport fleet. This can be both costly and technically complex. This paper proposes an analytical state estimator that can predict vehicle traffic count and spare power capacity under a traction substation without the use of any additional sensors. The estimator uses existing, locally available measurements at any power node on the traction section to inform the decision-making of the power management scheme at that node. Validating the results with up to 100000 stochastic test simulations of a verified traction grid model, up to 76% of the monitored conditions were detected, with no false positives, and without the need for additional sensors and wireless communication.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Design of a power electronic assisted series compensator for grid voltage regulation
No full textIn recent years, high penetration of distributed generation (DG) driven by PV panels and heavy load insertion in the distribution network has led to frequent voltage fluctuations in the form of undervoltage and overvoltage. Voltage control using traditional voltage regulators are unable to cope with this situation as frequent tap changes reduce the lifetime of the mechanical taps due to arcing. Further, the nature of European distribution network in general, makes voltage control through shunt compensation methods typically ineffective and expensive. Series compensation through centralized on-load tap changing (OLTC) distribution transformers or feeder-specific compensators is hence a suitable strategy for voltage regulation in Europe. The thesis work describes the design of a novel, power electronic assisted OLTC transformer that provides voltage regulation in the European distribution network through series compensation. The aim is to ensure that the tap changes occur in an arc free manner, thus providing for long lifetime of the OLTC. Different topologies for OLTC are examined in detail and shortlisted based on the steady state operation and power ratings of transformer and switches required. A novel design of a partially rated autotransformer is proposed which has taps developed through a combination of no-load switches and a single hybrid switch. The hybrid switch is composed of a mechanical switch and two semiconductor switches which are used for steady state and tap change operation respectively. The mechanical switch ensures low steady state losses and the semiconductor switches are used for arc-free tap changing. Back-back series connected IGBT with anti-parallel diodes are used for the two semiconductor switches and voltage polarity based 4-step commutation is used for commutation between the taps. The novel design of the OLTC autotransformer is cost effective, efficient and has long lifetime. The complete system is simulated in the PLECS and the steady state and transient operation of the system have been investigated. The OLTC has customized for application in both MV and LV three phase distribution network. Detailed study of the failure mechanisms owing to internal and external faults is performed and possible protection mechanisms are suggested. A low level control mechanism is also developed, thus providing a holistic design for building a prototype.Electrical Power ProcessingElectrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc
A Multi-Objective Design Approach for PV-Battery Assisted Fast Charging Stations Based on Real Data
No full textThis paper presents a multi-objective approach to designing an optimal PV-BES assisted EV fast charging station. The trade-offs between lifetime net present value (NPV), energy independence, and grid power reduction are analyzed using particle swarm optimization and real 50kW fast charging data. Our results show a maximum lifetime profit of close to 4M euro. Furthermore, for only a 8% decrease in profit the we can achieve up to 62% of the maximum energy independence and 46% peak power demand reduction. This show that EV fast charging stations can become more significantly more sustainable and have a less fluctuating demand, for very little reduction in profits.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
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