DC Fast Charging Research Articles

(Keynote) Current and Future Directions in Power Electronic Devices and Circuits Based on Wide Band-Gap Semiconductors

Electricity generation currently accounts for 40% of primary energy consumption in the U.S., and over the next 25 years is projected to increase more than 50% worldwide. Electricity continues to be the fastest growing form of end-use energy. Power electronics are responsible for controlling and converting electrical power to provide optimal conditions for transmission, distribution, and load-side consumption. Estimates suggest that the fraction of electricity processed through power electronics could be as high as 80% in the US by 2030 (including generation and consumption), approximately a twofold increase over the current proportion. Development of advanced power electronics with exceptional efficiency, reliability, functionality, and form factor will provide the U.S. with a competitive advantage in deployment of advanced energy technologies. Additionally, widespread integration of innovative converters offers substantial energy saving opportunities both directly, by inherently more efficient designs, and indirectly, by facilitating higher levels of adoption for fundamentally higher performing materials. High impact opportunities exist across a variety of applications, including power supplies, motor drives, automotive (including DC fast charging infrastructure), data centers, and aerospace, as well as grid and distributed energy resources (wind, solar PV, MV/HVDC, FACTS). Fast switching power semiconductor devices are the key to increasing the efficiency and reducing the size of power electronic systems. For the last three decades, silicon power devices (MOSFETS, IGBTs, and diodes) have dominated the power device market. During this time there have been tremendous improvements in silicon power device performance. However, these devices are now approaching the physical limits of silicon. Alternative wide-band gap semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN) are enabling a new generation of power devices that will far exceed the performance of silicon-based devices. Wide band-gap semiconductors enable continued improvement of the efficiency and reduced system size of power electronics. In this presentation, future directions in emerging wide bandgap semiconductor devices will be discussed. Furthermore, we will discuss the development and deployment of a new class of efficient, lightweight, and reliable power converters through transformational advances in circuit topologies, advanced control and drive electronics, and innovative packaging.

The Need for Charging: Evaluating utility infrastructures for electric vehicles while providing customer support

In 2011, at the beginning of the current electric vehicle (EV) market in the United States, the Electric Power Research Institute (EPRI) published a report [1] detailing certain aspects of the emergence of plug-in electric vehicles (PEVs), including the deployment of charging infrastructure, future impacts on the grid, and potential roles for electric utilities in supporting transportation electrification. Characteristics of this early market included a presumed reliance on home recharging and relatively low charging rates for the first two production vehicles (Chevrolet Volt and Nissan LEAF). The automotive industry had standardized around a common connector for charging from ac electricity at power levels up to 19.2 kW. A similar consensus had not been reached for dc fast charging (DCFC), but early deployment of a few 50-kW stations based on the CHAdeMO standard began, enabling a modest level of intercity travel for EVs with a practical range of about 80 mi.

Charging strategies for economic operations of electric vehicles in commercial applications

When substituting conventional with electric vehicles (EV) a high annual mileage is desirable from an environmental as well as an economic perspective. However, there are still significant technological limitations that need to be taken into consideration. This study presents and discusses five different charging strategies for two mobility applications executed during an early stage long-term field test from 2013 to 2015 in Germany, which main objective was to increase the utilization within the existing technological restrictions. During the field test seven EV drove more than 450,000km. For four out of five presented charging strategies the inclusion of DC fast charging is indispensable. Based on the empirical evidence five key performance indicators (KPI) are developed. These indicators give recommendations to economically deploy EV in commercial fleets. The results demonstrate that the more predictable the underlying mobility demand and the more technical information is available the better the charging strategies can be defined. Furthermore, the results indicate that a prudent mix of conventional and DC fast charging allows a high annual mileage while at the same time limiting avoidable harmful effects on the battery.

Expanding the Fast Charging Network

Oregon has more DC Fast Chargers (DCFC) for electric vehicles per capita than any other US region. This network has played a major role in making Oregon one of the strongest markets for electric vehicle sales in the US, despite the lack of a state purchase incentive. This paper summarizes Oregon’s experience with fast charging, evaluates the impact of this network, proposes new ways of defining network “success,” and makes recommendations for cost effectively expanding the network. These findings and recommendations should help inform other regions that are just beginning to build out their fast charging networks.

Implications of Successes and Failures of BEV-Focused Incentive Support for PEVs in the U.S., Canada and Europe

An international comparative analysis of causes of variation of PEV sales rates per capita in selected U.S. states, Canadian provinces, and European Nations is conducted. 2014-15 light-duty PEV registrations/sales by make and model are examined, drawing heavily on 2014 data for aggregate comparisons. States, provinces, and nations with PEV success, but with widely varying PEV purchase incentives and charging infrastructure installations are examined. The paper focuses particularly presence or absence of long daily distance charging options for PEVs. Four questions are addressed. (1) European evidence is that PHEV powertrains are a very marketable option for large family vehicles. For small BEVs BMW i3 sales patterns indicate that range extension beyond 120 km but less than 240 km via gasoline significantly increases market share. BEV inter-city functionality provided by aggressive installation of DC fast charging was critical to overall PEV success in Norway. Norway, like Northern Europe and Canada has a utility network that is winter peaking, which allows provision of peak summer BEV long-distance charging needs without difficulty. This is not the case for the U.S., which is summer peaking. The reviewed states, provinces, and nations vary considerably in seasonal peak temperature extremes. These climate differences have a significant bearing on the local viability of PHEVs vs. BEVs. The long distance DC fast charging infrastructure investments needed to support BEV market success are not as large when PHEVs are preferred by consumers.

Workload Patterns of Fast Charging Stations Along the German Autobahn

We analyze daily charging demand patterns of electric vehicles at DC fast charging stations along the German autobahn for an average week in 2020. For this we develop an agent based simulation tool based on current empirical mobility data. Our results show that already in 2020 about 1,000 charging processes per charging location and day might be realistic. In order to avoid long waiting times these charging locations should be equipped with about 20 charging points. A utilization rate of up to 80% makes a profitable operation of these stations highly probable. A sensitivity analysis indicates main parameters which influence the throughput of electric vehicles significantly.

An Integrated Global Philosophy of EV Charging

Electric Vehicle (EV) charging methods have evolved over the past two decades to reflect the radical evolution of EVs. In some cases these methods have been of varying usefulness to the EV driver. DC fast charging, which made a brief appearance in the late 90s, is now a valuable EV market enabler, but suffers from the political and technical disagreements of multiple protocols. Globally, EV charging will evolve further to meet the demands of the new consumer EVs and the demands of the EV driver. This paper proposes an integrated global philosophy to meet these demands.

Electric Vehicles: Impacts of Mileage Accumulation and Fast Charging

The impact of mileage accumulation and fast charging on driving range and battery energy of a light-duty battery electric vehicle (BEV), commercially available in North America, is being investigated. Two identical model BEVs are undergoing mileage accumulation on-road in Ottawa, Canada as well as testing on a chassis dynamometer in accordance with the SAE J1634 recommended test procedures. BEV1 is charged exclusively on DC fast-charging (DCFC) and BEV2 is charged exclusively on SAE AC Level 2 (ACL2). At the time of writing, the BEVs have been tested initially at 1,600 km, and then again after mileage accumulation to 15,000 km. Baseline results indicate that the two BEVs had a similar initial performance, and after 15,000 km the vehicles continue to have a similar driving range and useable battery energy despite the different charging methods. Both vehicles did, however, show decreased useable battery energy and recharge energy after 15,000 km of mileage accumulation and the resulting decrease in driving range varied between 0.4 and 13% depending on test conditions; these changes were not always statistically significant. Further testing is planned at approximately 15,000 km intervals up to 105,000 km. The next round of testing, at 34,000 km, will follow mileage accumulation at cold temperature, during an Ottawa, Canada winter.

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.

Battery cell balance of electric vehicles under fast-DC charging

Electric vehicle (EV) range, recharge opportunities and time to recharge are major barriers to mainstream acceptance. Fast-DC charging has the potential to overcome these barriers. This research investigates the impact of fast-DC charging on battery cell balance, charge capacity and range for an EV travelling long distances on an 'electric-highway'. Two commercially available EVs were exposed to a series of discharge and fast-DC charge cycles to measure cell balance and charge capacity. The vehicles' battery management systems (BMS) were capable of successfully balancing individual cells and hence maintaining the batteries' charge capacity. Although fast-DC charge levels and discharge safety margins significantly reduced the vehicles' charge capacity and range as stated by the manufacturer, these values remained stable for the test period. In regards to cell balance and charge capacity, our research suggests that fast-DC charging technology is a feasible option for EVs to travel large distances in a day.

Battery cell balance of electric vehicles under fast-DC charging

Battery cell balance of electric vehicles under fast-DC charging

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.

Analisis Teknologi Charger Untuk Kendaraan Listrik - Review

Electric vehicles are a choice for the future. Therefore, the electric vehicle will be spreads in the community. The public is the average consumer who does not have knowledge about electric vehicles, especially for problem charger. Charger technology in an Electric Vehicle Supply Equipment (EVSE) consists of three types, namely AC level 1, AC level 2 and DC fast charging. Each type has advantages and disadvantages. The disadvantage of AC level 1 type is take a long time for charging (about 20 hours) and the advantage is no risk of damaging the battery. AC level 2 has shortcomings that are still relatively long time to process the charge but shorter process than the AC charge level 1 and there is no high risk of damaging to the battery. DC fast charging has excesscharge process is very short (express)at range 20-30 minutes, but the disatvantage is very high risk of damaging the batteries in continuous usage.This paper also provide discussion for placement of any type of charger, so that people will understand.

The optimization of DC fast charging deployment in California

Battery electric vehicles (BEVs) are important for reducing fuel consumption and vehicle operating cost, and have the potential to reduce GHG and pollutant emissions. However, the range limits and long recharging times serve as obstacles to mass deployment. Well planned Level 3 DC fast charging stations are a potential solution to satisfy long distance travel demand instead of an expansive Level 2 non-home charging infrastructure. This paper identifies candidate charging routes and uses freeway exits and highway intersections as approximate candidate charging locations, and consequently solves a set covering problem to minimize the number of charging stations. Results show that 290 Level 3 charging locations are required for the State of California based on the 2000 California Travel Survey and BEVs with 60 mile range. With this optimized station network, electric light duty vehicle miles travelled (VMT) can reach 92% and BEVs can be used by 98% of drivers. If BEVs with 100 or 200 mile range are used, 126 or 31 Level 3 charging locations are required, respectively. This study also assesses the temporal utilization of charging stations. Congestion at several stations suggests extra chargers are required. A reservation system can benefit both the BEV drivers and station operators by reducing the wait times, decreasing the extra chargers needed, and more evenly utilizing all the stations. Related policies are also discussed to better deploy fast charging stations.

Giant-Magnetoresistance-Based Galvanically Isolated Voltage and Current Measurements

Nowadays, dc current is much more widely used than a decade ago, not only in the well-known high-voltage dc transmission but also as dc-powered marine systems, dc data centers, and dc fast charging systems for electric vehicles. However, galvanically isolated dc voltage or current sensors are, in terms of accuracy, noise level, or dimensions, still far behind the ac measurement devices in low and medium voltage areas. In this paper, a giant-magnetoresistive-based sensor system for galvanic isolated dc current and voltage measurements is introduced. The system mainly consists of a special coil arrangement with low inductance for voltage measurement, a special U-turn for current measurement, and A/D converters with a low-cost field-programmable gate array for signal conditioning. The sensor system showed an outstanding measurement accuracy of 0.3% for voltage values up to ±550 V and 0.2% for current values up to ±100 A in a temperature range from −30 °C to 90 °C. This completely new approach for the galvanically isolated measurement of electric voltage and current avoids the use of bulky magnetic components and expensive power-consuming analog electronics, which allows one to integrate it in the current ac measure unit for power monitoring.

Operation Analysis of Fast Charging Stations With Energy Demand Control of Electric Vehicles

For dc fast charging stations (FCS), short charging time duration is its main advantage over other ac charging stations. However, due to the characteristics of internal resistance of electric vehicle (EV) batteries, if charging request of an EV is near the full state of charge (SoC), its charging time increases significantly. In this paper, considering the impact of requested SoC on charging time, we propose an operation analysis of FCS, where operators of FCS can set a limit on the EVs' requested SoC to obtain maximized revenue. We model the FCS operation as an M/G/S/K queue and incorporate the dc fast charging model into the queuing analysis, as well as the revenue model of FCS. Simulation results indicate that limiting the requested SoC in an overloaded condition at FCS can increase total charged energy and revenue of FCS, as well as decrease the probability of blocking arriving EVs.

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.

Bi-directional electric vehicle fast charging station with novel reactive power compensation for voltage regulation

Excessive carbon emissions from the current transportation sector has encouraged the growth of electric vehicles. Despite the environmental and economical benefits electric vehicles charging will introduce negative impacts on the existing network operation. This paper examines the voltage impact due to electric vehicle fast charging in low voltage distribution network during the peak load condition. Simulation results show that fast charging of only six electric vehicles have driven the network to go beyond the safe operational voltage level. Therefore, a bi-directional DC fast charging station with novel control topology is proposed to solve the voltage drop problem. The switching of power converter modules of DC fast charging station are controlled to fast charge the electric vehicles with new constant current/reduced constant current approach. The control topology maintains the DC-link voltage at 800V and provides reactive power compensation to regulate the network bus voltage at the steady-state voltage or rated voltage (one per unit). The reactive power compensation is realized by simple direct-voltage control, which is capable of supplying sufficient reactive power to grid in situations where the electric vehicle is charging or electric vehicle is not receiving charges.

Conformance Testing for SGSF-064-1

A common conformance testing is needed before the modules equipped in the vehicle to ensure their design meet the standard requirements and capability to work together. In this paper SGSF-064-1 have been followed and its conformance testing items are described. SGSF-064-1 is the standard which provide communication interface for DC fast charging in Korea. We specially focused on the conformance testing when the vehicle is fully charged. We used TTC-3 language to perform simulation.

Evaluation of ground energy storage assisted electric vehicle DC fast charger for demand charge reduction and providing demand response

In 2012 there was approximately 2400 electric vehicle DC Fast Charging stations sold globally. According to Pike Research (Jerram and Gartner, 2012), it is anticipated that by 2020 there will be approximately 460,000 of them installed worldwide. A typical public DC fast charger delivers a maximum power output of 50 kW which allows a typical passenger vehicle to be 80% charged in 10–15 min, compared with 6–8 h for a 6.6 kW AC level 2 charging unit. While DC fast chargers offer users the convenience of being able to rapidly charge their vehicle, the unit's high power demand has the potential to put sudden strain on the electricity network, and incur significant demand charges.Depending on the utility rate structure, a DC fast charger can experience annual demand charges of several thousand dollars. Therefore in these cases there is an opportunity to mitigate or even avoid the demand charges incurred by coupling the unit with an appropriately sized energy storage system and coordinating the way in which it integrates. This paper explores the technical and economical suitability of coupling a ground energy storage system with a DC fast charge unit for mitigation or avoidance of demand charges and lessening the impact on the local electricity network. This paper also discusses the concept of having the system participate in demand response programs in order to provide grid support and to further improve the economic suitability of an energy storage system.