DC Charging Research Articles

Harmonic Distortion and Hosting Capacity in Electrical Distribution Systems with High Photovoltaic Penetration: The Impact of Electric Vehicles

Electric vehicles and the charging stations and their operation require a thorough examination to evaluate the effects on the electrical network. This becomes particularly challenging in the case of high photovoltaic penetration, due to the variability of the solar resource and vehicle connection patterns, which cater to individual user preferences. The current study investigates the impact of harmonics generated by charging stations and electric vehicles on different photovoltaic penetration scenarios within an electrical distribution system. DC and AC charging stations are analyzed. The findings reveal a third harmonic magnitude increase exceeding 300% compared to other cases. Furthermore, this study demonstrates the effects of current and voltage variations on end-users and substation transformers. The impact of harmonics on the hosting capacity of the network is also analyzed, resulting in a 37.5% reduction in the number of vehicles.

Data-Driven Modeling of Vehicle-to-Grid Flexibility in Korea

With the widespread use of electric vehicles (EVs), the potential to utilize them as flexible resources has increased. However, the existing vehicle-to-grid (V2G) studies have focused on V2G operation methods. The operational performance is limited by the amount of availability resources, which represents the flexibility. This study proposes a data-driven modeling method to estimate the V2G flexibility. A charging station is a control point connected to a power grid for V2G operation. Therefore, the charging stations’ statuses were analyzed by applying the basic queuing model with a dataset of 1008 chargers (785 AC chargers and 223 DC chargers) from 500 charging stations recorded in Korea. The basic queuing model obtained the long-term average status values of the stations over the entire time period. To estimate the V2G flexibility over time, a charging station status modeling method was proposed within a time interval. In the proposed method, the arrival rate and service time were modified according to the time interval, and the station status was expressed in a propagated form that considered the current and previous time slots. The simulation results showed that the proposed method effectively estimated the actual value within a 10% mean absolute percentage error. Moreover, the determination of V2G flexibility based on the charging station status is discussed herein. According to the results, the charging station status in the next time slot, as well as that in the current time slot, is affected by the V2G. Therefore, to estimate the V2G flexibility, the propagation effect must be considered.

Design and performance characterization of a new LISA-like (laser interferometer space antenna-like) gravitational reference sensor and torsion pendulum testbed.

In this paper, we present the design and performance of the upgraded University of Florida torsion pendulum facility for testing inertial sensor technology related to space-based gravitational wave observatories and geodesy missions. In particular, much work has been conducted on inertial sensor technology related to the Laser Interferometer Space Antenna (LISA) space gravitational wave observatory mission. A significant upgrade to the facility was the incorporation of a newly designed and fabricated LISA-like gravitational reference sensor (GRS) based on the LISA Pathfinder GRS. Its LISA-like geometry has allowed us to make noise measurements that are more representative of those in LISA and has allowed for the characterization of the mechanisms of noise induced on a LISA GRS and their underlying physics. Noise performance results and experiments exploring the effect of temperature gradients across the sensor will also be discussed. The LISA-like sensor also includes unique UV light injection geometries for UV LED based charge management. Pulsed and DC charge management experiments have been conducted using the University of Florida charge management group's technology readiness level 4 charge management device. These experiments have allowed for the testing of charge management system hardware and techniques as well as characterizations of the dynamics of GRS test mass charging. The work presented here demonstrates the upgraded torsion pendulum's ability to act as an effective testbed for GRS technology.

A Comprehensive Review of GaN-Based Bi-directional On-Board Charger Topologies and Modulation Methods

The wide-scale adoption and accelerated growth of electric vehicle (EV) use and increasing demand for faster charging necessitate the research and development of power electronic converters to achieve high-power, compact, and reliable EV charging solutions. Although the fast charging concept is often associated with off-board DC chargers, the importance of on-board AC fast charging is undeniable with the increasing battery capacities. This article comprehensively reviews gallium nitride (GaN) semiconductor-based bidirectional on-board charger (OBC) topologies used in both 400 V and 800 V EV applications. Moreover, comparative evaluations of GaN-based bi-directional OBC topologies regarding power conversion losses (conduction loss and soft switching capabilities), power density, implementation considerations, power quality, electromagnetic interference, and reliability aspects have been presented. The status of commercially available GaN power modules, advancements in GaN technology, applicable industry standards, and application requirements for OBCs have been also included in this study. Finally, in light of forthcoming advancements in GaN power transistor technology, this study highlights potential areas of research related to the reviewed topologies. Such research can aid researchers and designers in improving the performance and user experience of electric vehicles, ultimately supporting the widespread adoption of EVs.

Power Management in DC Microgrid by the DC-DC Converters

Abstract: DC loads have proliferated rapidly on the market today and DC micro grids with renewable energies are being built as a potential solution to meet the rising demand for electricity. As different energy sources such as solar, wind, fuel cell, and diesel generators can be incorporated into the DC grid, it is important to control the power flow between the sources. An attempt is made in this paper to study the hybrid system consisting a three energy sources, namely wind energy, photovoltaic power source and Battery. Each of the three energy sources is controlled so as to deliver uninterrupted power supply to the load. A control strategy for the management of power flows with solar and wind energy sources in DC micro grid are discussed. Given that voltage profile regulation is critical in a standalone system, a dedicated converter should be used to maintain the voltage of the DC connection. The battery circuit regulates DC charging voltage, while the full power is derived from Solar and Wind to power the attached DC bus charges. An algorithm is developed to manage power flow between three outlets. The algorithm is evaluated in MATLAB / SIMULINK environments for different charging conditions and variations in solar and wind energy.

A −31.7 dBm Sensitivity 0.011 mm2 CMOS On-Chip Rectifier for Microwave Wireless Power Transfer

This paper pursued both the lower operating power limit and small area of on-chip rectifiers for microwave wireless power transfer (MWPT). RF–DC charge pump rectifiers can operate in the fast switching limit at a high frequency of 920 MHz even with a small stage capacitor Cin of 100 fF, which contributes to an area reduction in the on-chip rectifiers. Circuit design starts with Cin determined as small as possible, followed by the determination of switching transistors and the number of stages. Even at an extremely low input power of 1 μW, wiring resistance in RF inputs is critical. Routing of the RF inputs is designed in line with stage capacitors. Bonding pad structure also affects the lower input power limit. Ground-shielded pad design can reduce the lower limit. Various types of RF–DC charge pump rectifiers are fabricated in 65 nm CMOS. An ultra-low-power diode RF–DC charge pump rectifier with 32 stages had a lower input power limit of −31.7 dBm at an output voltage of 1.0 V. Its small silicon area of 0.011 mm2 allows RF–DC rectifiers to be integrated in sensor ICs. More advanced technology providing MIM capacitors with higher capacitance density and placing switching MOSFETs under the MIM capacitors will further reduce the area of RF–DC charge pump rectifiers, allowing them to be integrated in sensor ICs.

Sistem Instalasi Pembangkit Pikohidro Untuk Keluaran Listrik Arus Searah 12 Volt

This research is focused to help peoples in remote areas who do not have electricity supply from PLN,but have sources of water flow in rivers. The main objective of this research is to create a picohydro hydroelectricpower plant with a floating turbine to utilize the kinetic energy of river water flow in areas that have not beensupplied with PLN electricity. The flow of water in the river will rotate the turbine, which in the end the rotationalpower is channeled through a pulley and belt system, which eventually turns an alternator. The alternator used isa three-phase AC alternator. Then the AC current will be rectified by the bridge rectifier to then be used to chargethe battery and go to the load. In addition, in this study, the ability of the pico-hydro system to supply electricalenergy will be tested to be able to run 12 V DC electrical loads and charge 12 V batteries.

A 120-kW electric vehicle DC charger with two charging guns

A 120-kW electric vehicle DC charger with two charging guns

DC Charging Capabilities of Battery-Integrated Modular Multilevel Converters Based on Maximum Tractive Power

The increase in the average global temperature is a consequence of high greenhouse gas emissions. Therefore, using alternative energy carriers that can replace fossil fuels, especially for automotive applications, is of high importance. Introducing more electronics into an automotive battery pack provides more precise control and increases the available energy from the pack. Battery-integrated modular multilevel converters (BI-MMCs) have high efficiency, improved controllability, and better fault isolation capability. However, integrating the battery and inverter influences the maximum DC charging power. Therefore, the DC charging capabilities of 5 3-phase BI-MMCs for a 40-ton commercial vehicle designed for a maximum tractive power of 400 kW was investigated. Two continuous DC charging scenarios are considered for two cases: the first considers the total number of submodules during traction, and the second increases the total number of submodules to ensure a maximum DC charging voltage of 1250 V. The investigation shows that both DC charging scenarios have similar maximum power between 1 and 3 MW. Altering the number of submodules increases the maximum DC charging power at the cost of increased losses.

Rotating Phase Shedding for Interleaved DC–DC Converter-Based EVs Fast DC Chargers

Fast dc chargers are the key enablers for the massive rollout of electric vehicles due to the reduced charging time. On the other hand, the rapid growth in battery technology with different voltages and charging requirements has imposed additional hurdles on the charger design to meet the efficiency requirements. Multiphase interleaved converters with conventional phase-shedding control improve the efficiency for a wide range of operations. However, they tend to operate certain phases, resulting in uneven thermal stress among the converter phases. This article proposes a rotating phase-shedding control to distribute the switching activities among all phases, enhancing the system's reliability while retaining the efficiency improvement. The proposed technique selects the proper number of active phases based on the required charging profile and periodically swaps them with other phases to even out the stress. The thermal profile is extracted to assess the thermal damage of the power switches. The performance of the proposed approach is evaluated and compared with the conventional phase shedding. The simulation and experimentally validated results confirm that the proposed technique achieves a better even distribution of the thermal damage between the phases compared with the conventional one. This will ultimately extend the lifetime of the system.

Design & Development Of a Dc Charging Unit For Various Engineering Applications

In this paper, the design & development of a DC charging unit for various engineering applications is presented. The DC Charger project is the creation of a charging system that converts AC power from the mains into a steady DC output for charging batteries and devices. The process involves using a transformer to step down the mains voltage, followed by a bridge rectifier that converts AC to pulsating DC. Smoothing capacitors then refine the DC waveform, which is further stabilized by voltage regulators to provide a consistent 12V output. A relay that manages the charging process. When the battery is fully charged, the relay disconnects the charging current. LED indicators provide visual cues for charging status. Protection mechanisms prevent issues such as overcurrent and overvoltage, ensuring safety. The project teaches about the basics of DC power electronics and how to design, build, components, and test a DC charger. It will also give you the opportunity to apply your skills in electronics and problem-solving. The work carried out is the second semester mini-project by the students of Electronics & Communication Engineering under the guidance of the faculties.

DC Charger Circuit Optimization Design and Fast Charging and Discharging Mechanism Research

DC Charger Circuit Optimization Design and Fast Charging and Discharging Mechanism Research

Traceability Technology of DC Electric Energy Metering for On-Site Inspection of Chargers

The on-site inspection of high-power DC chargers results in new DC high-current measurement and DC energy traceability system requirements. This paper studies the traceability technology of electric energy value for automotive high-power DC chargers, including: (1) the traceability method of the built-in DC energy meter and shunt of the charger; (2) precision DC high current and small precision DC voltage output and measurement technology. This paper designs a 0.1 mA~600 A DC high current measurement system and proposes a 0.005 level DC power measurement traceability system. The uncertainty evaluation experiment of the DC power measurement calibration system and the high-power DC charger’s on-site calibration experiment results verify the method’s effectiveness and feasibility in this paper. The experimental results show that the combined standard uncertainty of the DC power metering verification system can be 0.0451%.

Adaptive online auto-tuning using Particle Swarm optimized PI controller with time-variant approach for high accuracy and speed in Dual Active Bridge converter

<abstract> <p>Electric vehicles (EVs) are an emerging technology that contribute to reducing air pollution. This paper presents the development of a 200 kW DC charger for the vehicle-to-grid (V2G) application. The bidirectional dual active bridge (DAB) converter was the preferred fit for a high-power DC-DC conversion due its attractive features such as high power density and bidirectional power flow. A particle swarm optimization (PSO) algorithm was used to online auto-tune the optimal proportional gain (<italic>K<sub>P</sub></italic>) and integral gain (<italic>K<sub>I</sub></italic>) value with minimized error voltage. Then, knowing that the controller with fixed gains have limitation in its response during dynamic change, the PSO was improved to allow re-tuning and update the new <italic>K<sub>P</sub></italic> and <italic>K<sub>I</sub></italic> upon step changes or disturbances through a time-variant approach. The proposed controller, online auto-tuned PI using PSO with re-tuning (OPSO-PI-RT) and one-time (OPSO-PI-OT) execution were compared under desired output voltage step changes and load step changes in terms of steady-state error and dynamic performance. The OPSO-PI-RT method was a superior controller with 98.16% accuracy and faster controller with 85.28 s<sup>-1</sup> average speed compared to OPSO-PI-OT using controller hardware-in-the-loop (CHIL) approach.</p> </abstract>

Review on Unidirectional Non-Isolated High Gain DC–DC Converters for EV Sustainable DC Fast Charging Applications

Modern electrical transportation systems require eco-friendly refueling stations worldwide. This has attracted the interest of researchers toward a feasible optimal solution for electric vehicle (EV) charging stations. EV charging can be simply classified as Slow charging (domestic use), Fast charging and Ultrafast charging (commercial use). This study highlights recent advancements in commercial DC charging. The battery voltage varies widely from 36V to 900V according to the EVs. This study focuses on non-isolated unidirectional converters for off-board charging. Various standards and references for fast off-board charging have been proposed. Complete transportation is changed to EVs, which are charged by the grid supply obtained by burning natural fuels, contributing to environmental concerns. Sustainable charging from sustainable energy sources will make future EV completely eco-friendly transportation. The research gap in complete eco-friendly transit is located in interfacing sustainable energy sources and fast DC EV charging. The first step towards clean, eco-friendly transportation is identifying a suitable converter for bridging the research gap in this locality. A simple approach has been made to identify the suitable DC-DC converter for DC fast-charging EVs. This article carefully selected suitable topologies derived from Boost, SEPIC, Cuk, Luo, and Zeta converters for clean EV charging applications. A detailed study on the components count, voltage stress on the controlled and uncontrolled switches, voltage gain obtained, output voltage, power rating of the converters, switching frequency, efficiency obtained, and issues associated with the selected topologies are presented. The outcome of this study is presented as the research challenges or expectations of future converter topologies for charging.

12 Pulse High power Active Rectifier for Electric Vehicle Charging

The car industry pushes very fast toward electric vehicles (EVs). AC to DC charging stations pose big challenges for the power grid due to the heavy stress caused by electric-powered vehicles, especially when many vehicles are loading their accumulators simultaneously. The commercial success of electric vehicles (EVs) relies heavily on the presence of high-efficiency charging stations with low harmonics and a good power factor. To improve the power factor and boost the output voltage, this paper presents an analysis study and a simulation model of a 12-pulse high-power AC/DC active rectifier for EV charging stations. This converter topology provides bidirectional power flow and plays a double role as an AC to DC converter for power factor correction and as a DC converter for output regulation. The converter circuit is simulated using PSIM software, and results have observed. The simulation results for different conditions of operation are presented to highlight the feasibility and advantages of the proposed active rectifier.

Computational and Experimental Analysis of a Triode Microfuse with a WO3 Heater

In this study, high‐current‐protecting multilayered thin film microfuses are designed and simulated using the MEMS‐based tool of COMSOL multiphysics software and then fabricated and tested in the laboratory. Portable electronic devices are comprised of a secondary battery or DC charge source, and due to short circuit overcurrent, fire, and explosions can ensue. A protecting device should steadily cater to phenomena like overcurrent situations to avoid hazardous circumstances. The primary purpose of this investigation is to design a heater resistor with a negative temperature coefficient (NTC) to function as a low melting point‐based alloy for the fuse element. A lead‐tin (90Pb:10Sn wt.%) alloy has been employed as the low melting point‐based fuse element, and tungsten oxide (WO3) is integrated with the layer as a heater resistor due to its negative temperature coefficient of resistance characteristics. The electro‐thermo‐mechanical behavior is assessed, and a three‐dimensional structural modeling and simulation technique has been performed in both steady‐state and transient conditions with varying physical and electrical parameters. The heat required to melt the fuse depends on heater geometry, and when we applied 2 A current to the 1 : 30 length and width ratio‐based device, the heater achieved 600 K. Experimentally, nearly at 1 A current and above 4 V, the microfuse reached melting temperature and thus has been blown which provides a scope of controlling nearly 4 W of power electronic devices.

Agnostic Battery Management System Capacity Estimation for Electric Vehicles

Battery degradation is a main concern for electric vehicle (EV) users, and a reliable capacity estimation is of major importance. Every EV battery management system (BMS) provides a variety of information, including measured current and voltage, and estimated capacity of the battery. However, these estimations are not transparent and are manufacturer-specific, although measurement accuracy is unknown. This article uses extensive measurements from six diverse EVs to compare and assess capacity estimation with three different methods: (1) reading capacity estimation from the BMS through the central area network (CAN)-bus, (2) using an empirical capacity estimation (ECE) method with external current measurements, and (3) using the same method with measurements coming from the BMS. We show that the use of BMS current measurements provides consistent capacity estimation (a difference of approximately 1%) and can circumvent the need for costly experimental equipment and DC chargers. This data can simplify the ECE method only by using an on-board diagnostics port (OBDII) reader and an AC charger, as the car measures the current directly at the battery terminals.

Dual-Inverter-Integrated Three-Phase EV Charger Based on Split-Phase Machine

Significant effort has been dedicated to developing integrated onboard charging circuits for electric vehicles, aiming to improve cost, range anxiety, and charging convenience. The dual-inverter drivetrain topology has attracted particular attention as a platform for developing such solutions, being previously leveraged for the implementation of dc and single-phase ac onboard charging. This work proposes an integrated three-phase onboard charger based on the dual-inverter drivetrain. The proposed converter is implemented with minimal change to the dual inverter and no additional power electronics by introducing a split-phase electric machine. A mathematical model is developed, decomposing the system into four decoupled subsystems, individually responsible for charging, driving, grid common-mode current, and zero-sequence current generation, respectively. In light of this model, a novel space-vector pulsewidth modulation technique is introduced to ensure charging current control while generating no flux-producing, nor zero-sequence currents, and having superior common-mode performance. Simulation-based and experimental verification is conducted on a 7.2-kW scaled-down prototype to prove the charging concept, as well as the common-mode current elimination.

Re-design AC Power Failure Signal to Minimize False Signal of Emergency Shutdown System for Ethylene Plant

Chandra Asri, the largest integrated petrochemical company in Indonesia, requires a reliable electrical system to ensure production. Electrical power was supplied by the grid from PT. PLN through a 150 kV system in parallel with captive generation. The electrical system uses the Emergency Shutdown System (ESD) to protect against various disturbances that can cause equipment damage and work accidents. ESD will only work if things happen according to a logic diagram that has been designed according to the needs. One time, there was a power outage due to the active ESD. This causes huge losses for the company. The results of the investigation showed that there were no disturbances to either the grid or the captive generator. It is suspected that there is a false signal that causes the ESD to activate from the DC charger signal. For this reason, efforts are needed to eliminate the possibility of this nuisance signal occurring in the future by redesigning the logic and signal source of AC power failure by considering the existing secondary selective electrical system. Modification of the ESD system is carried out in 5 stages, namely 1) fault analysis, 2) modification of logic diagram design, 3) system development, 4) testing, and 5) evaluation. The results of the redesign decided that modifications should be made to the ESD system and carried out on the next Turn Around Maintenance schedule because this modification requires an offline electrical system. The analysis and simulation results show that the ESD system is safe against similar disturbances. It is hoped that the redesign and modification of the ESD system can prevent signal interference in the AC Power Failure Signal.