Showing papers on "Electric vehicle published in 1997"

Electric vehicles as a new power source for electric utilities

Abstract: Electric-drive vehicles, whether fueled by batteries or by liquid or gaseous fuels generating electricity on-board, will have value to electric utilities as power resources. The power capacity of the current internal combustion passenger vehicle fleet is enormous and under-utilized. In the United States, for example, the vehicle fleet has over 10 times the mechanical power of all current U.S. electrical generating plants and is idle over 95% of the day. Electric utilities could use battery vehicles as storage, or fuel cell and hybrid vehicles as generation. This paper analyzes vehicle battery storage in greatest detail, comparing three electric vehicle configurations over a range of driving requirements and electric utility demand conditions. Even when making unfavorable assumptions about the cost and lifetime of batteries, over a wide range of conditions the value to the utility of tapping vehicle electrical storage exceeds the cost of the two-way hook-up and reduced vehicle battery life. For example, even a currently-available electric vehicle, in a utility with medium value of peak power, could provide power at a net present cost to the vehicle owner of $955 and net present value to the utility of $2370. As an incentive to the vehicle owner, the utility might offer a vehicle purchase subsidy, lower electric rates, or purchase and maintenance of successive vehicle batteries. For a utility tapping vehicle power, the increased storage would provide system benefits such as reliability and lower costs, and would later facilitate large-scale integration of intermittent-renewable energy resources.

Propulsion system design of electric and hybrid vehicles

Abstract: There is a growing interest in electric and hybrid-electric vehicles due to environmental concerns. Efforts are directed toward developing an improved propulsion system for electric and hybrid-electric vehicles applications. This paper is aimed at developing the system design philosophies of electric and hybrid vehicle propulsion systems. The vehicles' dynamics are studied in an attempt to find an optimal torque-speed profile for the electric propulsion system. This study reveals that the vehicles' operational constraints, such as initial acceleration and grade, can be met with minimum power rating if the power train can be operated mostly in the constant power region. Several examples are presented to demonstrate the importance of the constant power operation. Operation of several candidate motors in the constant power region are also examined. Their behaviors are compared and conclusions are made.

An overview of power electronics in electric vehicles

Abstract: In response to concerns about energy cost, energy dependence, and environmental damage, a rekindling of interest in electric vehicles (EVs) has been obvious. Based on the "California rules" on zero emission vehicles in the United States, as well as similar tightened air pollution regulation in Europe, Asia, and much of the rest of the world, the market size of EVs will be enormous. Thus, the development of power electronics technology for EVs will take an accelerated pace to fulfil the market needs. This paper reviews the current status of multidisciplinary technologies in EVs. Various challenges of power electronics technology for EV propulsion, battery charging, and power accessories are explored.

Battery monitor for electric vehicles

Abstract: A battery monitor for monitoring the voltage and temperature of the batteries associated with a battery pack of an electric vehicle. The battery monitor includes an opto-isolator that electrically separates an isolated portion of the battery monitor connected to the batteries from a non-isolated portion of the battery monitor that transmits battery voltage and temperature signals to a vehicle controller of the electric vehicle. The battery monitor is positioned proximate to a battery tub holding the batteries of the electric vehicle so that high voltage wires connected to the batteries within the battery tub are limited in length for safety purposes. Further, a limited number of wires transmitting the battery voltage and battery temperature signals from the battery monitor to the vehicle controller are required. The battery monitor can include a multiplexer that selectively transmits the battery voltage and temperatures signals to the opto-isolator in a controlled manner, or can include a series of other opto-isolators that transmit high power battery signals to a capacitor to be charged where the charge on the capacitor is representative of the voltage of a particular battery.

Replaceable battery module for electric vehicle

Abstract: A system for "refueling" an electric vehicle includes a traction battery on a tray that is slidably disposed in a battery compartment of the vehicle and that is electrically connected to the traction motor of the vehicle. When the battery is depleted, the vehicle stops at an energy replenishment center which stores charged replacement traction batteries. The traction battery is electrically disengaged from the motor and the tray in the vehicle is slid out of the vehicle onto a dolly or into a receptacle of a carousel. Then, the replacement battery tray, which is disposed on another dolly or in another receptacle of the carousel, is juxtaposed with the battery compartment and slid into the compartment. Next, the fresh battery is electrically engaged with the motor, and the vehicle quickly resumes its journey. The depleted battery is recharged at the energy replenishment center and reused on a subsequent vehicle.

Design of an in-wheel motor for a solar-powered electric vehicle

Abstract: The design of an in-wheel electric motor for the solar-powered vehicle 'Aurora', entered in the 1996, 3010 km Darwin-Adelaide World Solar Challenge solar car race is described. Compared to other entrants in the race, the brushless DC motor is more efficient (97.5% compared to 92-95%) and lighter (8.3 kg compared to 12-16 kg) than all other direct-drive motors, and more efficient than all motor/gear combinations. This is achieved by the use of high flux-density rare-earth magnets, and computer aided optimisation of an axial-flux configuration consisting of a Halbach magnet array and an ironless air-gap winding.

Charge depletion control method and apparatus for hybrid powered vehicles

Abstract: A charge depletion method and apparatus for operating the electric motor and small auxiliary power unit, such as an internal combustion engine, in a hybrid electric vehicle (HEV) separately or together depending upon the driving conditions. Operation of the electric motor and auxiliary power unit are coordinated so that the vehicle operates as zero emissions vehicle (ZEV) or electric car at all speeds below a highway cruising threshold, unless the depth of discharge of the batteries exceeds a charge threshold in which case the vehicle operates in an HEV mode. Further, the vehicle operates in an HEV mode at speeds above the cruising threshold. The batteries are depleted during operation and are not charged by the auxiliary power unit, except during emergencies in which case the batteries are only charged enough to provide a performance enhancement to the small auxiliary power unit.

Thermal Performance of EV and HEV Battery Modules and Packs

Abstract: Thermal issues associated with electric vehicle (EV) and hybrid electric vehicle (HEV) battery packs can significantly affect performance and life cycle. Temperature variations from module to module in a battery pack could result in reduced performance. As part of the U.S. Department of Energy's Hybrid Propulsion Systems Program, the National Renewable Energy Laboratory (NREL) works with automobile and battery manufacturers on thermal analysis and management of valve-regulated lead-acid battery packs for HEVs. We use fundamental heat transfer principles and finite element analysis tools to predict the temperature distributions in cells, modules, and packs. We use infrared photography and liquid crystal thermography to obtain thermal images of the surface of battery modules under HEV charge/discharge profiles. In this paper, we provide an overview of related literature on battery thermal management, along with non-proprietary results of some of our work. Introduction The performance and life-cycle costs of electric vehicles (EV) and hybrid electric vehicles (HEV) depend inherently on energy storage systems such as batteries. Battery pack performance directly affects the all-electric (zero-emission) range, power for acceleration, fuel economy, and charge acceptance during energy recovery from regenerative braking. Because the battery pack cost, durability, and life also affect the cost and reliability of the vehicle, any parameter that affects the battery pack must be optimized. Battery module temperature uniformity is one such parameter. Depending on the electrochemical couple used in the battery, the optimum operating range is different. Some systems such as leadacid, NiCd, Li ion, and NiMH batteries operate reasonably well near room temperature. Other systems, such as Li polymers, may need to operate at elevated temperatures, and systems such as NaS require operating temperatures around 330C. These high-temperature systems need active thermal management systems. Battery systems that operate at ambient temperatures can also benefit from battery thermal management systems. Generally, higher temperatures improve the battery's performance because of increased electrochemical reaction rates; however, the battery's lifetime decreases because elevated temperatures increase corrosion. If temperature uniformity can be obtained within and between modules, then, the pack can operate closer to its desired optimum operating temperature range. Another important impact of a battery pack’s operating temperature is the electrical balance among modules in the pack. The performance of a battery pack depends on the performance of individual modules. If the cells and modules in the pack are at different temperatures, each module will be charged/discharged slightly differently during each cycle. After several cycles, modules in the pack will become unbalanced, degrading the pack’s performance. HEV charging/discharge profiles are generally more aggressive than those of EVs, which results in greater heat generation. EV batteries are high specific energy; HEV batteries are high specific power. Thermal issues in an HEV pack, then, are of more concern than thermal issues in an EV pack and thus, a thermal management system is required for HEVs. To optimize the performance of a battery pack, the thermal management system should deliver (1) optimum operating temperature range for all modules, (2) small temperature variations within a module, and (3) small temperature variations among various modules. However, the thermal management system must be compact and lightweight, easily packaged in the vehicle, reliable, and low-cost. It must also allow easy module access for service and use minimum power for fans and pumps. In this paper we provide an overview of heat generation in battery modules and of related work on batteries and EV packs. We then discuss the results of a thermal analysis in battery modules and packs, and thermal imaging techniques that can assist in evaluating the thermal behavior of modules and packs.

Method for controlling energy flow in a hybrid electric vehicle

Abstract: An operating strategy for a hybrid electric vehicle (HEV) manages the flow of energy to both supply the motive demand power of the HEV and maintain the charge of the energy storage system (ESS). A controller operates the main power unit (HPU) and ESS and, using an optimal fuel cost strategy, scans all possible combinations of power from the HPU and ESS that satisfy the motive demand power. The combination with the lowest fuel cost is selected and the ESS is charged, when possible, using marginal charging; but, if the state of charge of the ESS falls below a certain level, fast charging is invoked. A minimum power threshold strategy can be used rather than the fuel cost strategy. The minimum power threshold strategy determines the optimal compromise of HPU operation and ESS operation to maximize fuel economy by using a motive power threshold below which the HPU is not operated except to recharge the ESS.

A statistical method for predicting the net harmonic currents generated by a concentration of electric vehicle battery chargers

Abstract: This paper presents a method for predicting the net harmonic currents produced by a large number of electric vehicle (EV) battery chargers. The problem is stochastically formulated in order to account for randomness in individual charger start-time and battery state-of-charge. The authors introduce a model that allows for partial harmonics cancellation due to diversity in magnitudes and phase angles. A general solution technique is presented along with an example using data from a commercially available EV charger. Their results show that a limiting distribution of 7-10 chargers is adequate for accurately predicting harmonic injection currents using the central limit theorem. They also show that the expected values of net harmonic currents are considerably less than the peak values that would have been realized if the same number of chargers were operated in unison.

Advanced concepts in electric vehicle design

Abstract: In 1994, the Eco-Vehicle Project was begun to develop an electric vehicle (EV) using a ground-up design approach that incorporates unique designs specific to an EV. The Eco-Vehicle will be a high-performance, but ultrasmall, battery-powered vehicle. New designs for the Eco-Vehicle include an in-wheel motor drive system, a hollow load floor which will house the batteries, and a new battery management system. The Eco-Vehicle may also utilize other advanced concepts suitable especially for EVs, including solar panels for battery charging and intelligent crash avoidance and guidance systems.

Driving controller for electric vehicle

Abstract: A driving controller of electric vehicles. An angular accelerative dimension error calculator calculates error information having a dimension of angular acceleration of a car body. A feedback torque calculator calculates the feedback torque on the basis of the error information according to the sign of a steering angle and the error information, and ON/OFF of an accelerator. A vehicle controller corrects the reference torque, determined according to an accelerator angle and braking force, by the feedback torque, and outputs the corrected reference torque toward motor controllers, thereby improving vehicle running safety.

Power supply system, electric vehicle with power supply system mounted thereon, and method of regulating amount of fuel supply

Abstract: A power supply system 10 with a stack of fuel cells 20 and a storage battery 30 includes a remaining charge monitor 42 for measuring the remaining charge of the storage battery 30. At the time of starting the power supply system 10, the remaining charge monitor 42 detects the remaining charge of the storage battery 30. The power supply system 10 estimates output electric current of the fuel cells 20 based on the observed remaining charge of the storage battery 30 and an amount of electric power required for auxiliary machinery 34, and supplies required amounts of gases to the fuel cells 20 based on the estimated output electric current.

Method and apparatus for charging one or more electric vehicles

Abstract: A method and an apparatus for charging one or more electric vehicles includes a plurality of power converters (18, 20, 114, 116, 118, 158A, 158B, 158C, 158D) connectable to a source of electric power (14) to receive electric power therefrom. A switch (23) selectively connects the power converters (18, 20, 114, 116, 118, 158A, 158B, 158C, 158D) together to provide combined power to a first power coupler (22, 160A) in order to charge one electric vehicle, or connects the power converters (18, 20, 114, 116, 118, 158A, 158B, 158C, 158D) to separate power couplers (160B, 160C, 160D) in order to charge a plurality of vehicles.

Electric vehicle purchasing intentions: The concern over battery charge duration

Abstract: Exploratory research has been conducted to assess the relative importance of the factors which are most influential in discouraging the purchase of an electric car. In addition, trade-offs among the following factors: range, maximum speed, recharging time, and cost/delay in the case of a battery rundown, are estimated. Results point to a gap in the growing extant literature with respect to the high relative importance of the problems associated with a possible dead battery and that potential buyers may find these problems unacceptable, as is the case with problems associated with limited range and/or speed. The differentiation of preferences is examined with respect to socio-economic and demographic variables. The percentage of participants preferring a specific electric car concept is also compared with its average probability of being purchased.

Apparatus for displaying battery charging of electric vehicle

Abstract: An apparatus for displaying the charging of the battery of an electric vehicle has a charging connector mounted on an outer panel of a vehicle body of the electric vehicle, a lid openably mounted on the panel in covering relation to the charging connector and a cavity defined in the outer panel, and a display panel disposed in the cavity for displaying a period of time required until the battery is fully charged and/or a charged capacity of the battery. The driver of the electric vehicle can easily recognize the remaining time required until the battery is fully charged and a percentage of the fully charged capacity of the battery to which the battery is presently charged, from outside of the electric vehicle. The driver is not required to confirm the state of charge of the battery with an indicator on a battery charger or within the passenger's compartment of the electric vehicle, but can easily confirm the state of charge of the battery from outside of the electric vehicle.

Electric vehicle power supply

Abstract: To obtain an electric vehicle power supply 10 having a high output power density and regenerative power density, and which is compact and lightweight wherein a first battery 12 whose regenerative power density increases with decrease of the SOC and a second battery 14 whose output power density increases with increase of the SOC are used as an electrical storage device, and control is performed so that the SOC of the first battery 12 is maintained low while the SOC of the second battery 14 is maintained high. The regenerative power density of the first battery 12 is therefore high, the regeneration current from the motor 32 is mainly stored by the first battery 12, and the force used to drive the motor 32 is mainly output by the second battery 14 which has a high output power density.

Propeller wind charging system for electrical vehicle

Abstract: This invention relates to a multibladed (three or more) small diameter propeller as being included in an apparatus consisting of the single unenclosed propeller, extention shaft, armature shaft, and generator; such apparatus to be mounted on top of an electric vehicle to transform wind energy into electrical energy for feeding such energy into the battery pack as the vehicle is being driven forward; such energy to augment the stored voltage potential of the battery pack.

Power supply system, electric vehicle with power supply system mounted thereon, and method of charging storage battery included in power supply system

Abstract: A power supply system 10 with a stack of fuel cells 20 and a storage battery 30 includes a remaining charge monitor 46 for measuring the remaining charge of the storage battery 30. The remaining charge monitor 46 detects the remaining charge of the storage battery 30 at the time of stopping operation of the power supply system 10. In case that the remaining charge of the storage battery 30 is not greater than a predetermined level, the fuel cells 20 continuously charge the storage battery 30 until the remaining charge reaches the predetermined level. The power supply system 10 is stopped after the charging operation of the storage battery 30 has been accomplished. At a next start of the power supply system, the storage battery 30 functions as a primary power source to supply electric power to a loading until the warm-up of the fuel cells 20 is completed.

A permanent magnet hysteresis hybrid synchronous motor for electric vehicles

Abstract: This paper presents the design, analysis and PWM vector control of a hybrid permanent magnet hysteresis synchronous (PMHS) motor with a view to improve the performances of motors for electric vehicle applications. This hybrid design combines the advantageous performance features of both conventional hysteresis motors and permanent magnet motors. Electrical equivalent circuits of the PMHS motor are developed for both the synchronous and asynchronous modes of operation. PWM vector control simulation results for the motor drives are given. Finally, a laboratory prototype hybrid hysteresis permanent magnet motor was built. Test results validate the superior performances of the new motor.

A procedure for derating a substation transformer in the presence of widespread electric vehicle battery charging

Abstract: This paper studies the effect of electric vehicle (EV) battery charging on a substation transformer that supplies commercial, residential, industrial, and EV load on a peak summer day. The analysis begins by modeling non-EV load with typical utility load shapes. EV load is modeled using the results from an analytical solution technique that predicts the net power and harmonic currents generated by a group of EV battery chargers. We evaluate the amount of transformer derating by maintaining constant daily transformer loss-of-life, with and without EV charging. This analysis shows that the time of day and the length of time during which the EVs begin charging are critical in determining the amount of transformer derating required. Our results show that with proper control, EV charging may have very little effect on power system components at the substation level.

Electric vehicle charging system including refrigerant system

Abstract: A charging system for use with an electric vehicle in that a primary coil 32 is structured in such a manner that a conductive pipe 34 is wound around a primary core 33. Cooling water is allowed to circulate through the conductive pipe 34, while the cooling water is cooled by a radiator device provided on the charging unit side. To the two ends of the conductive pipe 34, there are connected the core wires of a charging power cable 40 through energizing terminals 37, so that the primary coil 32 can be excited.

Power supply unit and electric vehicle incorporating the same

Abstract: A power supply unit has a capacitor unit for supplying electric power to a load. The capacitor unit has at least two blocks each having a plurality of electric double-layer capacitors connected in series. The manner of connection of the at least two blocks is changed over between series connection and parallel connection in dependence on an output required by the load. A switching regulator is connected to the electric charge-storing device. An electric vehicle having the power supply unit installed thereon is also provided.

Traction control of electric vehicle based on the estimation of road surface condition-basic experimental results using the test EV "UOT Electric March"

Abstract: The most distinct advantage of an electric vehicle is in its quick and precise torque generation. The authors propose two novel traction control techniques of electric vehicles: model-following control; and optimal slip ratio control. Their effectiveness is demonstrated by using the "UOT Electric March" test vehicle.

Hybrid electric vehicles

Abstract: Many experts believe the hybrid electric vehicle (HEV) should be the car of the near future. In simple terms, an HEV is an electric ar that also has a small internal-combustion engine and an electric generator on board to charge the batteries, thereby extending the vehicle's range. The batteries may be charged continuously or only when they become depleted to some level. Thus, HEVs do not share an electric vehicle's main drawback: limited range between chargings. The few thousand electric vehicles on the roads in the U.S. today can travel only about 130 km (80 miles) before their batteries need recharging, which can take up to eight hours. The power of a hybrid's internal-combustion engine generally ranges from one tenth to one quarter that of a conventional automobile's. If HEVs ever become a success in the U.S., there could be benefits both for the environment and for the balance of trade: imported petroleum now accounts for almost half of the country's consumption.

Fuel-cells system, electric vehicle with fuel-cells system, and method of controlling supply of electric power

Abstract: In a fuel-cells system 10 including a stack of fuel cells 20 and a storage battery 30, the remaining charge of the storage battery 30 is measured by a remaining charge monitor 46. In case that the observed remaining charge of the storage battery 30 is less than a predetermined reference value, a control unit 50 outputs a driving signal to an inverter 80, in order to restrict the consumption of electric power by a motor 32. When it is determined that the output state of the storage battery 30 is in the discharging state, based on the output electric current of the storage battery 30 measured by a current sensor 90, the control unit 50 further limits the electric power consumed by the motor 32. These processes are repeatedly carried out to charge the storage battery 30 and recover the remaining charge of the storage battery 30 to a sufficient level.

Direct-hydrogen-fueled proton-exchange-membrane fuel cell system for transportation applications

Abstract: In partial fulfillment of the U.S. Department of Energy Contract No. DE-ACO2-94CE50389, {open_quotes}Direct Hydrogen-Fueled Proton-Exchange-Membrane (PEM) Fuel Cell System for Transportation Applications{close_quotes}, this conceptual vehicle design report addresses the design and packaging of battery augmented fuel cell powertrain vehicles. This report supplements the {open_quotes}Conceptual Vehicle Design Report - Pure Fuel Cell Powertrain Vehicle{close_quotes} and includes a cost study of the fuel cell power system. The three classes of vehicles considered in this design and packaging exercise are the same vehicle classes that were studied in the previous report: the Aspire, representing the small vehicle class; the AIV (Aluminum Intensive Vehicle) Sable, representing the mid-size vehicle; and the E-150 Econoline, representing the van-size class. A preliminary PEM fuel cell power system manufacturing cost study is also presented. As in the case of the previous report concerning the {open_quotes}Pure Fuel Cell Powertrain Vehicle{close_quotes}, the same assumptions are made for the fuel cell power system. These assumptions are fuel cell system power densities of 0.33 kW/ka and 0.33 kW/l, platinum catalyst loading of less than or equal to 0.25 mg/cm{sup 2} total, and hydrogen tanks containing compressed gaseous hydrogen under 340 atm (5000 psia) pressure. The batteries considered for power augmentation of the fuel cell vehicle are based on the Ford Hybrid Electric Vehicle (HEV) program. These are state-of-the-art high power lead acid batteries with power densities ranging from 0.8 kW/kg to 2 kW/kg. The results reported here show that battery augmentation provides the fuel cell vehicle with a power source to meet instant high power demand for acceleration and start-up. Based on the assumptions made in this report, the packaging of the battery augmented fuel cell vehicle appears to be as feasible as the packaging of the pure fuel cell powered vehicle.

Magnetic coupling device for charging an electric vehicle

Abstract: In a magnetic coupling device for charging an electric vehicle which is used for charging a power storage device of the electric vehicle by means of a charging power source, a primary coil unit is inserted into a receiving unit which is on an electric vehicle and in which a secondary coil unit is disposed. In the device, junction faces of primary and secondary cores are formed in the insertion direction of the primary coil unit, and primary and secondary coils are disposed at positions where, when the primary coil unit 30 is inserted, the primary and secondary coils do not interfere with each other. Wiping members which wipe the junction faces are disposed. The insertion direction of the primary coil unit is in parallel with the longitudinal direction of the unit.

Modeling power consumption by electric vehicles and its impact on power demand

Abstract: Electric vehicles are expected to be one of the means to level the difference between the peak time and off-peak time electric loads. From a global point of view, increasing environmental concerns make us recognize the necessity of replacing conventional gasoline cars by electric vehicles. Due to problems with the efficiency and life time of a battery, it will take time before electric vehicles are in general use. Electric vehicles are used only in specialized small fields. Automobile makers are cooperating to invent advanced batteries for use in electric vehicle. Thus, it is timely to develop appropriate infrastructure standards and technologies to make electric vehicles attractive to consumers. In this paper, we investigate the impact of electric vehicle on electricity demands by assuming analytical models of EV consumption. The charging characteristics of a battery, the running performance, and the practical driving distance of each type of car are used in this analysis. According to the scenario analysis, the simulations clearly presented the impact of EV introduction using the practical day load duration curve for the Tokyo cosmopolitan area. The authors conclude that electric vehicles are effective for load leveling under some sort of market regulations. If there is no regulation in the EV market, power shortage will occur on both nighttime and daytime because of the concentration of the nighttime charge and the quick charge. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(4): 40–47, 1997