DC Charging Research Articles

Feasibility study of a grid-tied 2MW floating solar PV power station and e-transportation facility using ‘SketchUp Pro’ for the proposed smart city of Pondicherry in India

The race of smart cities in India places Pondicherry at 75th position. To improve its ranking position for smart city race, we propose the implementation of 2MW Floating Solar Photovoltaic (FSPV) system -where a large water body could be used for generation of solar power. The floating PV system can be used to attain much higher efficiency compared to its counterpart on land based PV system. The proposed FSPV system could cover solar panel of 1/3rd area of the proposed lake to generates 2685 MWh annually. A geo-synchronized layout has been prepared using 3D SketchUp Pro with Google maps. The FSPV system could cost USD 1.6 million with a payback period of 6 years. In addition, the implementation of e-transport facility by utilizing e-rickshaws with a battery capacity of 90Ah with 15 Amps DC charging facility has been proposed with an investment of USD 30k, with payback period of just 5 month. The bright side being improved overall payback due to money inflow with the implementation of e-rickshaws; greater job opportunities with benefits to physically challenged persons to improve their overall socio economic status. It is viewed that the proposed FSPV and e-transport could increase the chance to secure smart city plan for Pondicherry.

Phase-resolved detection of the spin Hall angle by optical ferromagnetic resonance in perpendicularly magnetized thin films

The conversion of charge current to spin current by the spin Hall effect is of considerable current interest from both fundamental and technological perspectives. Measurement of the spin Hall angle, especially for atomically thin systems with large magnetic anisotropies, is not straightforward. Here we demonstrate a hybrid phase-resolved optical-electrical ferromagnetic resonance method that we show can robustly determine the spin Hall angle in heavy-metal/ferromagnet bilayer systems with large perpendicular magnetic anisotropy. We present an analytical model of the ferromagnetic resonance spectrum in the presence of the spin Hall effect, in which the spin Hall angle can be directly determined from the changes in the amplitude response as a function of the spin current that is generated from a dc charge current passing through the heavy-metal layer. Increased sensitivity to the spin current is achieved by operation under conditions for which the magnetic potential is shallowest at the ``Smit point.'' Study of the phase response reveals that the spin Hall angle can be reliably extracted from a simplified measurement that does not require scanning over time or magnetic field but rather only on the dc current. The method is applied to the Pt-Co/Ni/Co system whose spin Hall angle was to date characterized only indirectly and that is especially relevant for spin-orbit torque devices.

On The Strategies for the Diffusion of EVs: Comparison between Norway and Italy

The aim of this work is to estimate e-mobility trends, which are crucial for understanding the market and the infrastructure expansion over the next years and debate which are the persuasive policies to improve the diffusion. At the present time between the numerous and diverse standards and rules there are two charging types for electric vehicles: high power DC and AC charging modes. It will be stimulating to understand which technology will overcome in the following few years and if the charging mode option on a given electric vehicle (EV) affects its sales results. This paper addresses the existing e-mobility scenario in Norway and Italy, in particular evaluating: EV technical and commercial features, EV market connected to national incentive strategies, technical and diffusion connector type and charging mode. In conclusion, based on the existing history and analysis of the informations accessible, this work presents a measured outlook on the probable progress of this expanding niche market

Feasibility study of a grid-tied 2MW floating solar PV power station and e-transportation facility using ‘SketchUp Pro’ for the proposed smart city of Pondicherry in India

The race of smart cities in India places Pondicherry at 75 th position. To improve its ranking position for smart city race, we propose the implementation of 2MW Floating Solar Photovoltaic (FSPV) system -where a large water body could be used for generation of solar power. The floating PV system can be used to attain much higher efficiency compared to its counterpart on land based PV system. The proposed FSPV system could cover solar panel of 1/3 rd area of the proposed lake to generates 2685 MWh annually. A geo-synchronized layout has been prepared using 3D SketchUp Pro with Google maps. The FSPV system could cost USD 1.6 million with a payback period of 6 years. In addition, the implementation of e-transport facility by utilizing e-rickshaws with a battery capacity of 90Ah with 15 Amps DC charging facility has been proposed with an investment of USD 30k, with payback period of just 5 month. The bright side being improved overall payback due to money inflow with the implementation of e-rickshaws; greater job opportunities with benefits to physically challenged persons to improve their overall socio economic status. It is viewed that the proposed FSPV and e-transport could increase the chance to secure smart city plan for Pondicherry.

Performance Testing and Power Quality of DC Semi-Fast Chargers of Electric Vehicles (EVs) for Public Transportation: a Case Study

This paper contains the analysis of the impact, performance, and effect on power quality of the semi-fast charging cycle of electric vehicles (EVs) within the electrical grid. The results allowed to obtain an electric model of the EV charging cycle. The procedures and results of tests on the DC semi-fast charging cycle of EVs used for the public transportation in Bogota D.C. are presented. Some tests to the EV charging cycle were applied in steady state in order to evaluate the performance and the power quality of EVs. The fact that the charging system has a total harmonic current distortion (THDi) of 7% and a total harmonic voltage distortion (THDv) that satisfactorily comply with local and international regulations is highlighted. Tests were performed in transient state of the charger and their analysis was done by using Continuous Wavelet Transform (CWT). Results in transient state of the beginning of the DC charging cycle of EVs reveal that the harmonics of greater impact are 3°, 4°, and 5°. Finally, based on the analysis of the presented results, a simulation profile of the charging system was designed using the Matlab Sim Power Systems tool. The obtained model shows an error of 2% compared to measurements in steady state. This model will be useful in decision-making on the processes of system planning in case that EVs will be massified within the public transportation in Colombia.

Integration between electric vehicle charging and PV system to increase self-consumption of an office application

The paper analyzes the introduction of a photovoltaic system satisfying electric, space heating and cooling demand of an office building located in southern Italy. The electric load is due to an electric heat pump, used to satisfy space heating and cooling load, a pure electric demand (personal computers, printers, lighting, etc.) and an electric vehicle charged during working hours. Dynamic simulations to evaluate the energy and environmental performance of the analyzed system considering different photovoltaic peak powers (4.5–9.0kW), electric vehicle distance per day (40–120km) and charging mode is carried out. The solar based system shows primary energy saving and equivalent carbon dioxide emission reduction higher than 40% in comparison to the reference conventional system based on a natural gas fired boiler, an electric chiller and a diesel car. The results highlight that the solar energy system is more competitive when DC charging system is provided.

Chevrolet Volt on-road test programs in Canada part 1: Effects of drive cycle, ambient temperature and accessory usage on energy consumption and all-electric range

Environment Canada (EC) and Natural Resources Canada (NRCan) separately tested two 2012 Chevrolet Volts between 2013 and 2014 in Ottawa, Ontario on public roads in the summer and winter months using realistic cabin-climate control settings. More than 1300 trips were conducted over nine routes: three city, one congested, two arterial, one highway and two expressway routes. EC tests recorded cabin conditioning, traction battery and 12 V accessory power, select vehicle component temperatures, regulated emission rates and exhaust flow, and DC charge energy. Both NRCan and EC tests measured cumulative electrically driven distance (all-electric range), select CANbus signals and AC grid supply charge energy. Results from these studies were analysed to evaluate the overall performance of the Chevrolet Volt on public roads in climates representative of most of Canada (-27 °C to 37 °C) using realistic accessory settings. At 25 °C the Chevrolet Volt’s on-road all-electric EPA-method adjusted range is generally less than the U.S. EPA sticker rating (57.9 km). Cabin conditioning energy was found to be directly related to the difference between ambient and cabin temperature, except at low temperatures (< 0 °C) when the 1.4 L engine activates to assist the thermal management system. On average, heating the cabin in the winter months consumed significantly more electric energy than cooling the cabin in the summer months. Summer city and highway driving resulted in the lowest energy consumption (Wh/km), while congested and expressway driving cycles resulted in the highest. In the winter months, many differences between the drive cycles were not discernible due to the high cabin conditioning energy consumptions.

Wide-angle KTa1−xNbxO3 deflector for swept light source using DC charge technique

A 5-pass KTa1−xNbxO3 (KTN) deflector based on a DC charge technique for the swept light source of an optical coherence tomography system is proposed. The DC charge technique used in a 3-pass KTN deflector enables us to obtain the long-term stability of the optical power without any degradation of the important features of the swept light source. Experimental results confirm that the coherence length of a swept light source with the 5-pass KTN deflector using the DC charge technique is almost equal to that using a precharge technique reported previously. This means that the DC charge technique does not degrade the coherence length. There are limitation values for applied voltage, the KTN electrode gap, relative dielectric constant, and sweep frequency of the KTN deflector in terms of obtaining long coherence length. We believe that a 7-pass KTN deflector is effective for obtaining a longer coherence length.

Relaxation times and charge conductivity of silicene

We investigate the transport and single particle relaxation times of silicene in the presence of neutral and charged impurities. The static charge conductivity is studied using the semiclassical Boltzmann formalism when the spin-orbit interaction is taken into account. The screening is modeled within Thomas-Fermi and random phase approximations. We show that the transport relaxation time is always longer than the single particle one. Easy electrical controllability of both carrier density and band gap in this buckled two-dimensional structure makes it a suitable candidate for several electronic and optoelectronic applications. In particular, we observe that the dc charge conductivity could be easily controlled through an external electric field, a very promising feature for applications as electrical switches and transistors. Our findings would be qualitatively valid for other buckled honeycomb lattices of the same family, such as germanine and stanine.

Design of a 12-MW HTS Wind Power Generator Including a Flux Pump Exciter

A flux pump (FP) exciter injects dc current into the high-temperature superconducting (HTS) field coils of an HTS rotating machine without a slip ring and current leads. When designing a large-scale HTS generator with integrated FP exciter, the coil inductance, field current, and time constant need to be optimized for better performance of the machine. In this paper, a 12-MW HTS wind power generator with integrated FP exciter was designed. The essential parameters of a 12-MW HTS generator were optimized using the Taguchi method, targeting the minimization of weight and volume of the generator, the length of HTS wire, and the inductance. In particular, the FP exciter was adopted for supplying dc current to the HTS field coils without the power supply and the slip ring. The magnetic field distribution was analyzed using the 3-D finite-element method. The induced dc current and charging and discharging times of the FP exciter were compared with the metal current leads, for confirmation of the effectiveness of the FP exciter. The detailed results of the HTS generator design were discussed in detail.

E-Mobility Forecast for the Transnational e-Corridor Planning

This paper evaluates the trend of fast dc charging systems (combining the trends of the infrastructure and of the vehicles) to verify the feasibility of the development of an infrastructure of transnational corridors that can guarantee the accessibility for all vehicles. This paper starts with the real-life situation characterized by multiple disjointed projects in many countries to verify whether, in spite of the different solutions employed, it is possible to find a common trend that can become a guideline for future projects. A predictive model for the e-mobility trend is developed to understand the market and the development of the infrastructure over the next few years. The results are used to identify how to equip European transnational corridors with fast dc charging stations, and a study case is presented.

IMPACT OF PENETRATION OF ELECTRIC VEHICLES ON INDIAN POWER GRID

The research on impacts of electric vehicles on Indian power grid is motivated to enhance development of electric vehicle in India against the burning issues of rising fuel demand and the nation’s dependency on other countries for fuel which largely affects the GDP of nation. India has declared E-mobility mission plan to deploy 4,00,000 passenger electric vehicles by 2020. If this target is achieved India can avoid importing 120 million barrels of oil and avoid 4 million tonnes of CO2 emissions by 2020. In future, as demand of electric vehicles increases, charging issues while connecting electric vehicle to grid also increases. This paper presents various aspects in terms of challenges and issues when electric vehicle is charged from grid and also the benefits, potential services and applications of electric vehicle in V2G mode. Effect of electric vehicle penetration on distribution grid is carried out in matlab simulink environment to observe effects on different electrical parameters like dc bus voltage, current, active power, reactive power, harmonics and power factor. Concept of vector control technique for voltage source converter is developed for stabilizing grid against penetration of electric vehicle. Control technique implemented here gives fast dynamic response, reduces harmonics and improves power factor with constant dc bus voltage. Concept shown here will be very useful for fast dc charging of electric vehicle batteries. Battery modelling described with the concept of extracting parameters from manufacturers discharge characteristics gives fast and effective solution and will be useful for not only Li-Ion batteries but also for Ni-Mh and Lead-acid batteries.

Dual Active Bridge-Based Battery Charger for Plug-in Hybrid Electric Vehicle With Charging Current Containing Low Frequency Ripple

Manufacturers want high power density for the on-board battery chargers of plug-in hybrid electric vehicles. Wide bandgap devices can be used to shrink other passive components by increasing the switching frequency, but the bulk dc link capacitor of the ac-dc power factor correction stage, becomes one of the major barriers to higher power density, because its volume depends on the ripple power at the double line frequency in a dc current charging system. However, if this double line frequency ripple flows into the battery, the dc link capacitance can be significantly reduced. This charging scheme, named as sinusoidal charging in this paper, is analyzed and implemented based on a two-stage battery charging system, which is comprised of one full bridge ac-dc stage and one dual active bridge dc-dc stage. We further find that converter loss causes ripple power imbalance and bigger dc link capacitance. Therefore, the impact of converter loss on the ripple power balance is analyzed, and a feedback control on the dc link voltage ripple is proposed based on this analysis in order to further reduce the dc link capacitance. The effectiveness of the proposed solutions is verified in both Si-based and GaN-based charging systems.

Split Converter-Fed SRM Drive for Flexible Charging in EV/HEV Applications

Electric vehicles (EVs) and hybrid EVs are the way forward for green transportation and for establishing low-carbon economy. This paper presents a split converter-fed four-phase switched reluctance motor (SRM) drive to realize flexible integrated charging functions (dc and ac sources). The machine is featured with a central-tapped winding node, eight stator slots, and six rotor poles (8/6). In the driving mode, the developed topology has the same characteristics as the traditional asymmetric bridge topology but better fault tolerance. The proposed system supports battery energy balance and on-board dc and ac charging. When connecting with an ac power grid, the proposed topology has a merit of the multilevel converter; the charging current control can be achieved by the improved hysteresis control. The energy flow between the two batteries is balanced by the hysteresis control based on their state-of-charge conditions. Simulation results in MATLAB/Simulink and experiments on a 150-W prototype SRM validate the effectiveness of the proposed technologies, which may provide a solution to EV charging issues associated with significant infrastructure requirements.

Radio frequency reflectometry and charge sensing of a precision placed donor in silicon

We compare charge transitions on a deterministic single P donor in silicon using radio frequency reflectometry measurements with a tunnel coupled reservoir and DC charge sensing using a capacitively coupled single electron transistor (SET). By measuring the conductance through the SET and comparing this with the phase shift of the reflected radio frequency (RF) excitation from the reservoir, we can discriminate between charge transfer within the SET channel and tunneling between the donor and reservoir. The RF measurement allows observation of donor electron transitions at every charge degeneracy point in contrast to the SET conductance signal where charge transitions are only observed at triple points. The tunnel coupled reservoir has the advantage of a large effective lever arm (∼35%), allowing us to independently extract a neutral donor charging energy ∼62 ± 17 meV. These results demonstrate that we can replace three terminal transistors by a single terminal dispersive reservoir, promising for high bandwidth scalable donor control and readout.

Experimental study of a DC charging station for full electric and plug in hybrid vehicles

Abstract This paper is aimed to analyze design criteria, setting up, control strategies and experimental tests related to a power configuration of DC micro-grid for fast charging of full electric and plug in hybrid vehicles. The proposed DC fast charging architecture is derived by an analysis comparing the main characteristics of well known architectures, mainly based on AC and DC bus, taking also into account the integration of renewable energy sources (RESs) with stationary energy storage systems and fleets of road electric/hybrid vehicles. On the base of the proposed architecture a laboratory prototype of charging station has been realized by means of a 20 kW AC/DC bidirectional grid tie converter interconnected with two different power DC/DC converters of similar rated power. In this micro-grid architecture the AC/DC converter realizes a conversion stage at 790 V DC, whereas other two converters allow either the electric vehicle battery packs to be charged or an energy storage buffer to save electric energy and support the main grid during the fast charging operations. The laboratory tests described in this paper are mainly devoted to characterize the laboratory demonstrator, in different operative conditions, such as vehicle-to-grid (V2G), charging/discharging operations of different types of storage systems and fast charging operations of road electric vehicles. Then the study of the proposed power conversion architecture is focused on the evaluation of charging/discharging power, efficiency, energy flux management and its impact on the main grid. In addition proper control strategies are evaluated and implemented, allowing the proposed architecture to follow the required operations. The obtained experimental results demonstrate real advantages in terms of charging times and power requirements from the main grid, when adopting DC buffer architecture for fast charging operations. Finally, these results support the identification of a knowledge base, useful to evaluate energy management and control strategies to be adopted for DC charging stations and each one of their power converters in a smart grid scenario with distributed generation systems.

Modeling and Simulation of DC Microgrids for Electric Vehicle Charging Stations

This paper focuses on the evaluation of theoretical and numerical aspects related to an original DC microgrid power architecture for efficient charging of plug-in electric vehicles (PEVs). The proposed DC microgrid is based on photovoltaic array (PVA) generation, electrochemical storage, and grid connection; it is assumed that PEVs have a direct access to their DC charger input. As opposed to conventional power architecture designs, the PVA is coupled directly on the DC link without a static converter, which implies no DC voltage stabilization, increasing energy efficiency, and reducing control complexity. Based on a real-time rule-based algorithm, the proposed power management allows self-consumption according to PVA power production and storage constraints, and the public grid is seen only as back-up. The first phase of modeling aims to evaluate the main energy flows within the proposed DC microgrid architecture and to identify the control structure and the power management strategies. For this, an original model is obtained by applying the Energetic Macroscopic Representation formalism, which allows deducing the control design using Maximum Control Structure. The second phase of simulation is based on the numerical characterization of the DC microgrid components and the energy management strategies, which consider the power source requirements, charging times of different PEVs, electrochemical storage ageing, and grid power limitations for injection mode. The simulation results show the validity of the model and the feasibility of the proposed DC microgrid power architecture which presents good performance in terms of total efficiency and simplified control.

Charge transport in gapless electron-hole systems with arbitrary band dispersion

Using the semiclassical Boltzmann transport theory, we analytically consider dc charge transport in gapless electron-hole (both chiral and non-chiral) systems in the presence of resistive scattering due to static disorder arising from random quenched impurities in the background. We obtain the dependence of the Boltzmann conductivity on carrier density and temperature for arbitrary band dispersion in arbitrary dimensionality assuming long-range ($\sim 1/r$) Coulomb disorder and zero-range white noise disorder [$\sim \delta(r)$]. We establish that the temperature and the density dependence of the Boltzmann conductivity manifests scaling behaviors determining respectively the intrinsic semimetallic or the extrinsic metallic property of the gapless system. Our results apply equally well to both chiral and non-chiral gapless systems, and provide a qualitative understanding of the dependence of the Boltzmann conductivity on the band dispersion in arbitrary dimensionality.

Experimental evaluation of DC charging architecture for fully-electrified low-power two-wheeler

This paper is aimed to present an experimental criterion that allows researchers and designers to evaluate the performance of DC micro-grids dedicated to charging operations of full EV. The laboratory methodology is explained through tests on a demonstrator of power architecture, specifically designed as simplified case study of a DC charging station for fully-electrified low-power two-wheeler, such as: electric scooters and bikes. This experimental prototype is composed by a 20kW AC/DC bidirectional grid-tied converter, which realizes the DC conversion stage, and two DC/DC power converters, interconnected with the micro-grid through a DC bus. The power architecture provides on one hand the charging operations of electric two-wheeler battery packs and on the other hand the integration of the micro-grid with an ES buffer, which has the main function of supporting the main grid while an electric vehicle is on charge. The performance of the considered architecture is characterized and analyzed in different operative conditions, through a specific management of the energy fluxes. The laboratory tests evaluate efficiency, charging times and impact on the main grid, with specific reference to the DC charging operations of electric scooters. The obtained experimental results show the advantages of adopting the DC buffer architecture, compared with an AC commercial battery charger, considered as reference in this work. Finally, the numerical data of this paper, related to the single power components and to the experimental results evaluated for the whole demonstrator, effectively support the lack of knowledge in the literature about charging stations for EVs. In fact, these pieces of information, based on experimental tests, are expected to support the building of simulation models and the identification of the best energy management and control strategies to be adopted in a smart-grid scenario, characterized by distributed generation systems including renewable energy sources.

Chevrolet Volt On-Road Test Programs in Canada Part 1: Effects of Drive Cycle, Ambient Temperature and Accessory Usage on Energy Consumption and Electric Range

Environment Canada (EC) and Natural Resources Canada (NRCan) separately tested two 2012 Chevrolet Volts between 2013 and 2014 in Ottawa, Ontario on public roads in the summer and winter months using realistic cabin-climate control settings. More than 1300 trips were conducted over nine routes: three city, one congested, two arterial, one highway and two expressway routes. EC tests recorded cabin conditioning, traction battery and 12V accessory power, select vehicle component temperatures, regulated emission rates and exhaust flow, and DC charge energy. Both NRCan and EC tests measured cumulative electric distance, select CANbus signals and AC grid supply charge energy. Results from these studies were analysed to evaluate the overall performance of the Chevrolet Volt on public roads in climates representative of most of Canada (-27°C to 37°C) using realistic accessory settings. At warm temperatures (~25°C) the Chevrolet Volt’s on-road all-electric range generally exceeded the U.S. EPA sticker rating (57.9km), while at cold (&lt;0°C) and hot temperatures (&gt;25°C) the all-electric range decreased to as low as 27.5km and 47.3km, respectively. Cabin conditioning energy was found to be directly related to the difference between ambient and cabin temperature, except at low temperatures (&lt;0°C) when the 1.4L engine activates to assist the thermal management system. On average, heating the cabin in the winter months consumed significantly more electric energy than cooling the cabin in the summer months. Summer city and highway driving resulted in the lowest energy consumption (Wh/km), while congested and expressway driving cycles resulted in the highest. In the winter months, many differences between the drive cycles were not discernible due to the high cabin conditioning energy consumptions.