DC Charging Research Articles

A Noninductive Bifilar Coil to Design Compact Flux Pumps for HTS Magnets

High-temperature superconducting (HTS) flux pump is a promising way of energizing superconducting magnets without direct electrical contacts. It can remove the resistive heating and heat leakage from the current leads at room temperature. It is well known that applying the current over the critical current of the superconductor will force the superconducting layer to enter into the flux flow regime. This flux flow resistivity generates a dc voltage across the length of the HTS tape. This phenomenon is well understood; however, it is difficult to generate a high dc charging voltage without a high current. In this article, we demonstrate a novel flux pumping technique by using a noninductive bifilar bridge wound in parallel to the HTS coil. This configuration can generate large dc voltages using relatively small currents. It results in effectively pumping dc currents equal to the critical current for large HTS magnets.

An Explicit Thermal Resistance Model Regarding Self-Heating Effect of AlGaN/GaN High Electron Mobility Transistor

This paper introduced an accurate empirical model for the thermal resistance of a single-finger AlGaN-GaN high electron mobility transistor (HEMT) on three different substrates including Sapphire, SiC and Si. The model reckons the constant thermal conductivity of GaN and substrate, thickness of host substrate layers, gate length (Lg) and width (Wg). The model plausibility is verified by comparing it with DC channel temperature measurement method and charge controlled based device modeling which agrees very favorable observation of the model data. Having nimble expression for the channel temperature is of inordinate importance in the field of designers of power device and monolithic microwave integrated circuits. Proposed model gives a variety of inquiries that would be impossible or impractical to do using time-consuming numerical simulations.

Research on the design and verification of the charging compatibility for electric vehicle ChaoJi charging

The international mainstream DC charging systems CHAdeMO 2.0 in Japan, GB/T 2015 in China, CCS1/CCS2 in Europe, and the U.S. have different control pilot circuit and the coupler designs. Control pilot circuit is an important component of the electric vehicle (EV) charging system and is used to monitor the function of the interaction between the EV and the electric vehicle supply equipment (EVSE). Existing system designs can make the difficult to achieve the compatibility between different charging systems, and reduce the user experience. This study first analyzes the practical applications of four existing mainstream DC charging systems. There are certain defects in structural design, safety, compatibility, and control pilot function, the introduction of a new generation of ChaoJi charging technology will change all these. Meanwhile the vehicle adapter design solution can perfectly solve the problem of physical compatibility between the existing charging system and ChaoJi vehicle. In addition, a new control pilot circuit design is proposed, to identify normal charging and abnormal states by hard node signals and states switches. By building a test environment, this new control pilot circuit has proven to its excellent characteristics in terms of fault monitoring, backward compatibility, and future-proof applications. ChaoJi charging technology has been adopted by CHAdeMO 3.0, laying the foundation for a globally harmonized charging system.

Development and Validation of V2G Technology for Electric Vehicle Chargers Using Combo CCS Type 2 Connector Standards

Vehicle-to-Grid (V2G) technology is viewed as a viable solution to offer auxiliary power system services. Currently, V2G operation is only possible through DC chargers using the CHAdeMO connector with the necessary communication protocol. However, in Europe, for high-power DC charging (>50 kW), the Combined Charging Service (CCS) Type 2 is preferred over CHAdeMO. Therefore, this work presents the development of a V2G testing system with a Combo CCSType 2 charger including communication via the ISO 15118-2 protocol. The BOSCH passenger car with a 400 V battery pack is used to test and validate the technical feasibility of V2G charging via a Combo CCS Type 2 connector standard. The V2G feature is characterized in terms of efficiency, signal delay, response proportionality, magnitude accuracy and noise precision. A data driven V2G charger simulation model based on the real-time data is also developed in MATLAB/Simulink. The performance under various operating settings is presented in the outcomes, emphasizing the need for appropriate hardware calibration, and understanding while delivering standard-compliant grid control services using V2G technology. Finally, the results of the simulation model are compared with the real hardware results in terms of error, noise level and data magnitude accuracy.

Toward Nonlinear Galloping Energy Harvesting Interfaced With Different Power Extraction Circuits

While there has been a surge of study on nonlinear aeroelastic energy harvesting structures for enhanced wind power extraction, there is a gap in the literature on the integration of advanced power conditioning circuits with these mechanically sophisticated nonlinear structures. This article presents an investigation on the influence of different voltage processing interface circuits on the power generation performance in nonlinear galloping energy harvesting. Cubic hardening, cubic softening, and bistable configurations are studied. Their mechanical and electrical responses associated with the simple ac, standard dc, and synchronous charge extraction (SCE) circuits analyzed and compared. Results show that with the ac and standard dc circuits, the bistable and cubic hardening configurations are superior to the cubic softening configuration, generating comparably high power outputs with beneficially small displacements. The SCE circuit significantly boosts the power generation of the two monostable (cubic hardening and softening) harvester designs, but degrades the performance of the bistable design by trapping the oscillation within a single potential well over a large wind speed range. The findings form a baseline for future enhancement in the design of nonlinear aeroelastic wind power generators.

A multi‐layer framework for energy efficiency assessment of shore‐to‐ship fast charging systems including onshore batteries

This paper proposes a three-layer framework for energy efficiency evaluation of Shore-to-Ship Charging (S2SC) systems using load-dependent loss models of the components. The considered S2SC system is supplied by the grid but is also supported by On-Shore Batteries (OSB). The presented approach is then used to investigate the impact of the specific design and operational parameters on energy efficiency. Power system architectures for three general S2SC solutions for ac, dc, and inductive charging are defined and compared in terms of energy efficiency. Operational parameters are also considered in the analysis, namely, the grid power ratio, determining the load sharing between the grid and the OSB, as well as the OSB charging profile. A case study is performed with peak charging power of 1 MW, and the most efficient S2SC solutions are identified for both ac- and dc-based onboard power systems. Moreover, it is shown that charging OSB with the highest available power from the grid between the charging breaks would often lead to higher energy efficiency than the maximum utilization of the available charging time. Field data from a real S2SC system is used to verify the estimated energy efficiency by the proposed framework. The analysis of the real case S2SC is then extended to include and verify a projected OSB.

Sodium-pillared vanadium oxides as next-gen materials: Does co-inserted water control the cyclic stability of vanadates in an aqueous electrolyte?

Layered vanadium oxides are, due to their adaptable interlayer distance and a multivalent state of vanadium, interesting electrode materials for various kinds of metal-ion batteries with both aqueous and nonaqueous electrolytes. In this study, a precursor solution adjusted for hydrothermal synthesis of sodium vanadate Na2V6O16, is modified by addition of carbon nanopowder Vulcan XC72, and this suspension is used for an one-pot hydrothermal synthesis of sodium vanadate/C composite. XRD analysis evidenced that the obtained composite is the mixture of two vanadate phases: Na2V6O16 and NaV6O15, instead of expected single-phase vanadate. SEM and TEM observations of composite revealed that these vanadate phases emerge in a form of both nanowires and nanospheres. The heterogeneity of phases and morphology of the composite is attributed to the directional action of carbon nanoparticles as a nucleation seed. The composite, used in aqueous Li-ion battery with LiFe0.95V0.05PO4/C cathode and LiNO3 electrolyte, displayed improved charge storage (220 mAh g−1 at current rate 150 mA g−1 in the initial discharge), after dc charging, in comparison to NaV6O15 or Na2V6O16 nanowire anodes. Furthermore, versatile insertion capability of this heterostructured composite towards mono (Li+, Na+) and multivalent (Ca2+, Mg2+, Al3+) ions in aqueous electrolytes is demonstrated by Cyclic Voltametry method, where the capacity stability depends on the type of cation, following the order Al3+, Li+, Mg2+, Ca2+. Upon 100 potentiodynamic chaging/discharging cycles, Ca2+ions display much better capacitance retention than Li+ ions (i.e., 64 vs. 13% of the initial value). The coinserted electrolyte constituents, H2O and OH− species, are considered to be responsible for the improved capacity retention, making vanadium ions less strained and less soluble. The pH, the concentration of the electrolyte and the type of anion are found to influence the cyclic behavior of observed vanadate composite in Ca-containing electrolyte. These results open a new directions in vanadate electrochemistry towards more sustainaible and cheaper aqueous batteries.

Scheduling and Routing of Mobile Charging Stations With Stochastic Travel Times to Service Heterogeneous Spatiotemporal Electric Vehicle Charging Requests With Time Windows

This article presents an alternative service of mobile charging stations for the large-scale charging of electric vehicles, which consider the spatiotemporal heterogeneity of charging requests. As charging infrastructure is the key determinant for the large-scale adoption of electric vehicles, state-of-the-art scheduling and control strategies need to be explored. The charging of electric vehicles in a conventional charging station even with the fast dc–dc chargers takes around 30 min, which results in congestion and large waiting queues at public charging stations. To account for this issue, a novel strategy of routing and scheduling mobile charging stations to charge electric vehicles without the constraints of time and space is discussed in detail. Furthermore, the traveling times of mobile charging stations in reality are stochastic in nature. We formulate the optimization problem to minimize the cost of charging and show that the problem formulated is a combination of a bin packing problem and a multicity traveling salesman problem; hence, it is NP-hard and cannot be solved in reasonable CPU time, unless P = NP. We, thus, present modified saving’s heuristic and modified genetic algorithm metaheuristic to solve the optimization problem. Furthermore, numerical simulations show that the proposed scheduling and routing algorithm requires less number of mobile charging stations and can appreciably reduce the cost of charging.

Design and Development of Pull Type Battery Operated Multi-crop Planter for Woman Farmers in Tribal Region of Gujarat

In tribal region of Gujarat women are the integral part of the farming system. They transform mostly all kinds of work. Manual seed sowing consumes much energy as well as time. For maintaining uniformity in planting seed to seed distance should be accurate. Most existing manual seed sowing devices don’t have this facility. To provide a better option, a multi-crop planter was developed with electric metering at College of Agricultural Engineering and Technology, Godhra for woman farmer in tribal region of Gujarat. Multi-crop planter consists of main frame, handle, furrow opener, seed tube, marker, metering mechanism, DC battery (12V), DC motor, DC speed regulator, switch and DC charger. The payback period of developed machine was found as 53.42 hours on hour basis and 6 ha on hectare basis. The benefit cost ratio of the developed multi-crop planter was found as 14.97 over a period of 10 years of the life of the multi-crop planter.

Study on the DC supply and charging effect on the growth of carbon nanotubes and their electrochemical properties

Study on the DC supply and charging effect on the growth of carbon nanotubes and their electrochemical properties

Fast Charging of an Electric Bus Fleet and Its Impact on the Power Quality Based on On-Site Measurements

The subject of this study was a distribution substation that feeds 14 fast DC chargers (80 kW) located at the bus depot in Lublin, Poland. The voltage variations were determined to be within the PN-EN 50160 standard limit values (±10% Un). There were several events registered when 4th, 6th, 8th, and 10th voltage harmonics were above the PN-EN 50160 limit during the charging of the electric buses. The obtained maximum 10 min average values of the total voltage harmonic distortion (THD) were 3.36%, 2.27%, and 2.89% for the first, second, and third phase, respectively, i.e., below the limit value of 8% required by PN-EN 50160. Due to the exceedance of the 6th voltage harmonic, the PN-EN 50160 requirements were not met.

Checking of the condition of transformers and the efficiency of oil regeneration with RVM (return voltage measurement)

Up to now the insulation in HV power transformers has been made from oil/paper therefore the diagnosis of this kind of insulation will be also important in the next forty-fifty years. The lifetime of this equipment strongly depends on the condition of the insulation system. The ageing process of oil/paper insulating systems is a very complex and complicated phenomenon. In order to get a well-supported decision on the further operation of aged transformers, relevant information would be necessary on the condition of the oil-paper insulation. We also know that the oil-paper insulation has almost always inhomogeneous condition considering the temperature, moistening and ageing processes. The classical methods (insulation resistance, loss tangent, etc.) characterise the insulation by single measured value. This single value is not sufficient for relevant characterisation and diagnosis of such a complex system with lots of tons of insulation and with almost always inhomogeneous distribution of temperature, moisture and ageing product. If we measure the polarization spectra in three states (new insulation in equilibrium and uniform polarization spectrum, new insulation with not uniform distribution of polarization spectrum, later reaching again the uniform distributions) the shape of three polarization spectra will be different. Comparing the polarization and classical methods of this three case we can realize that sometimes the “classical single values” are almost the same but the polarization spectra are different. The three response methods provide very practical information about the insulation system (e.g. moisture, ageing). The moistening and accumulation of ageing by-products change the distribution of interfacial polarisation in the range of long time-constants. These promising response methods measure the polarisation distribution in the range of long time-constant (with other words, in the low frequency range). The three test methods were: Return Voltage measurement (RVM), the C and tgδ measurement in range of some tens of mHz to 50 Hz (FDS=Frequency Domain Spectroscopy), and the measurement of DC charging and discharging currents (PDC=polarisation and depolarization currents) up to some thousands of sec. These equivalent methods (RVM, FDS and PDC) are able to follow the changing of condition of insulation contrary to classical methods. Therefore a little bit surprising that until now the convenient standards is missing considering the polarization methods. In an earlier Hungarian research work (Budapest University of Technology) almost all the necessary measurements have been realized, consequently we are in possession of fundamental data considering the polarization methods. This paper would like to show a short review about the RVM technique, the correct interpretation of RVM data and a case study for the checking of the efficiency of the oil reclamation with RVM technique.

Modelling of Micro Hydropower System for Small Load Application

The implementation of Movement Control Order (MCO) to curb the spread of covid-19 in Malaysia has resulted in an increased financial burden on the people especially those from the low-income group. Therefore, taking advantage of the promising renewable energy as the free source of electricity could subsequently reduce the financial burden borne by this group. Hence, this paper conducts an analysis using MATLAB/Simulink software, to assess the viability of small-scale hydro turbines in converting potential energy of water heads into electricity for powering small load appliances. The analysis consists of several parts such as the DC generator, converter and charge controller. The data regarding volume of water usage in this study is based on water usage by the author. The result from simulation through the MATLAB software demonstrate a convincing reading in recorded voltage, current and power which indicate this system is feasible for electrification of small load appliances and indicate the potential for future improvement and research.

Temporal-spatial scheduling of electric vehicles in AC/DC distribution networks

With the rapid development of power electronic technology, the AC/DC hybrid distribution network has become a new trend of distribution system architectures in recent years. And meanwhile, electric vehicles (EVs) equipped with both AC and DC charging interfaces tend to be utilized as ideally dispatchable resources in not only temporal but also spatial dimensions, whose charging/discharging schemes remarkably impact the secure and economical operation of distribution networks. In view of this background, this paper proposes a temporal-spatial scheduling model of EVs in AC/DC distribution networks, targeting at the optimum of the whole network losses as well as the inconveniences of EV users originated from following scheduling instructions. Besides the traditional constraints relevant to EVs’ temporal scheduling in just-AC distribution networks, the AC/DC hybrid topology and the restrictions for EVs’ spatial scheduling are properly involved in the proposed model. After a reasonable simplification procedure, the proposed model is represented as a Mixed Integer Quadratic Program (MIQP) problem that can be efficiently solved by off-the-shelf optimization algorithms. Through the analyses of a coupled electrical-geographical AC/DC distribution network, the proposed model can bring 6.3% and 6.8% cost savings respectively on two typical days.

Dynamic event‐triggered model predictive control of Vienna rectifiers in DC charging system

Here, a dynamic event-triggered model predictive control (DETMPC) of Vienna rectifiers in the DC charging system is proposed to solve the excessive calculation burden of the conventional MPC method while maintaining the system performance. The status of the system is constantly updated, and the next model predictive control calculation is performed only when the system state meets the event-triggered condition. Otherwise, the original switch state signal is maintained, which can greatly reduce the computational burden. A dynamic variable is introduced into the trigger condition to holdover the steady-state performance as the system state changes. An experimental comparative analysis is carried out to verify the correctness and effectiveness of the proposed DETMPC method. The results demonstrate that the proposed method can effectively reduce calculation burden and switching loss while maintaining satisfactory system performance at the same time.

Electric-Drive-Reconstructed Onboard Charger for Solar-Powered Electric Vehicles Incorporating Six-Phase Machine

In this article, a novel electric-drive-reconstructed onboard charger (EDROC) is proposed for the solar-powered electric vehicle that incorporates a six-phase machine drive. The power traction inverter and the machine are re-leveraged to implement charging operation, further minimizing the incremental mass accordingly. In particular, charging and driving operations can be simultaneously carried out via the vehicle-roof photovoltaic panels, significantly expanding EV mileage range. First, the operation scenario and the topology of the proposed EDROC are introduced. Next, the operational principle is analyzed, as well as the indispensable conditions for safe and stable operation are studied. Thereafter, control schemes are designed and elaborated in terms of the simultaneous driving and charging mode and the dc charging mode. To this end, a 2-kW laboratory prototype is conducted, and experimental results are presented to verify the steady-state and dynamic behavior of the proposed EDROC system under different operation modes.

Design of DC Accumulator Charging using Backup Accumulator Based on Inverter and Converter Device

<p>The charging of DC accumulator that<br />experiences a lack of electric charge energy, usually<br />utilizes an AC input power from the PLN network. When<br />the AC input power from the PLN network is unavailable,<br />a DC power source is used from the backup DC<br />accumulator as a substitute. The research objective is to<br />design an internal DC accumulator charging using a<br />backup DC accumulator equipment based on inverter<br />and converter equipment. The charging system will use<br />input power from the backup DC accumulator to replace<br />the AC input power from the PLN network. The electric<br />voltage of the internal DC accumulator that is filled<br />(charged) is the initial condition of V<br />DC(Acu.Int.)= 8.76 Volts<br />until it reaches the normal condition of 12.05 Volts with a<br />capacity of charging current of 5 Ah (Ampere.hours)<br />absorbs electrical energy of W(Acu.Int.)<br /> = 16.45 Wh(Watt.hours). The results show that the equipment supply<br />a DC charger of 13.0 volts and PDC<br />of 21.32 watts to theinternal DC accumulator. The comparison of W<br />(Acu.Int.) to PDC produces time charging, t(charging)of 46.29 minutes</p>

Dc electrical current generated by upstream neutral modes

Quantum Hall phases are gapped in the bulk but support chiral edge modes, both charged and neutral. Here we consider a circuit where the path from the source of electric current to the drain necessarily passes through a segment consisting solely of neutral modes. We find that upon biasing the source, a dc electric current is detected at the drain, provided there is backscattering between counter-propagating modes under the contacts placed in certain locations. Thus, neutral modes carry information that can be used to nonlocally reconstruct a dc charge current. Our protocol can be used to detect any neutral mode that counterpropagates with respect to all charge modes. Our protocol applies not only to the edge modes of a quantum Hall system, but also to systems that have neutral modes of non-quantum Hall origin. We conclude with a possible experimental realization of this phenomenon.

A comparative study of AC and DC public electric vehicle charging station usage in Western Australia

DC fast-charging stations can charge an electric vehicle several times faster than Level 2 AC charging stations. Using a network of DC charging stations, it becomes possible to travel in electric vehicles for long-distance, cross-country driving with only short recharging stops. This paper examines and compares typical customer usage patterns at DC fast-charging stations (50 kW) against Level 2 AC charging stations (7 kW) to study the benefits of transitioning to DC charging for Western Australia. It includes data collected from The University of Western Australia’s AC and DC charging network in the Perth metropolitan area and stations along the highway connecting Perth to Augusta in the rural South West of Western Australia (over 300 km apart). A cost model is drawn up to calculate the local operating cost and break-even requirement across several different styles of charging stations. User behaviour and the adoption of certain charging infrastructures are crucial for the general uptake of electric vehicles. Notwithstanding, national electric vehicle charging standards and infrastructure availability have a fundamental influence on the electrification of transport.

Control Design of a 99% Efficiency Transformerless EV Charger Providing Standardized Grid Services

A nonisolated DC charger is proposed for electric vehicle (EV) battery system. The leakage current can be reduced by the novel charging system without bulky transformer. A zero sequence voltage control method is developed to stabilize the common-mode voltage, thus, reduce the leakage current. The proposed fast charger includes two energy conversion stages: DC–DC converter for battery side control; DC–AC converter for grid interface and common-mode voltage control. The parameters of the system with the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter are analyzed and optimized for a better performance of grid interface. Grid service functions are designed for the EV charger to provide grid-voltage/frequency compensations. High power (22 kW) and high efficiency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 99%) are achieved with low-leakage current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&lt;$</tex-math></inline-formula> 20 mA). The experiments are implemented to verify the proposed EV charger system.