Worldwide, the automotive industry is being challenged to make dramatic improvements in vehicle fuel economy. In Europe there are CO2 emissions penalties prorated by the degree to which vehicles exceed mandated CO2 levels. In the United States, vehicle fuel economy targets set by Congress in 2007 for 20 per cent fuel economy improvement by 2020 are now being accelerated by the Obama administration to 35.5 mpg by 2016 for a passenger car. Taking effect in 2012, the new rules set more aggressive fuel economy measures that will require significant gains in engine and driveline efficiency, better performance cabin climate control and the introduction of electric hybridization. This 2nd Edition of Propulsion Systems for Hybrid Vehicles addresses the electrification innovations that will be required, ranging from low end brake energy recuperators, idle-stop systems and mild hybrids on to strong hybrids of the power split architecture in both single mode and two mode and introducing new topics in plug-in hybrid and battery electrics. Important topics of the 1st Edition are retained and expanded and some outdated material has been replaced with new information.
Inspec keywords: transportation; power electronics; hybrid electric vehicles; electric drives; energy storage
Other keywords: energy storage; power electronic; hybrid power plant; drive system control; hybrid vehicle; automated electrified transportation; AC drive; electric drive system
Subjects: Drives; Electric actuators and final control equipment; Transportation system control; Power convertors and power supplies to apparatus; Transportation
When the first edition of this book was written in 2003, the following statement was made: 'More visionary companies see hybrid vehicles as viable long term environmental solutions during the period when ICEs evolve to cleaner and more efficient power plants.' At the time of writing, some six years later, this statement has proven correct as the following citations will illustrate. In Reference 1, Rishi et al. state, 'A new era is rapidly approaching in which the very definition of personal mobility will change. Multi-modal transportation will become increasingly common, and intelligent vehicles will cater to diverse consumer needs for informa tion, environmental responsibility and safety.' This was followed by an even more provocative statement that the next 10 years will see more change than the previous 50 years. The pace of change is accelerating. This in fact is the motivation for releasing this second edition to Propulsion Systems for Hybrid Vehicles.
We know now that no particular power train architecture would be suitable for all vehicles in all markets. Today, pre-transmission parallel and power split architectures have found their principal application in passenger vehicles in the compact and mid-size segments. Series and series-parallel switching architectures are either in production or under prototype development for city buses, commercial trucks and other heavy vehicles. Subcompact and compact vehicles, including minivans, are being converted to continuously variable transmission (CVT) hybrids where the CVT, generally of the belt type, has integrated into it the traction M/G. Because of the high actuation forces necessary in a CVT, an ancillary electric drive for the oil pump is necessary, generally in the 2-2.5 kW power rating. Higher rated power split and series-parallel shifting configurations are being introduced in small sport utility and larger vehicles. Fuel cell powered vehicles are strictly series hybrids because electric propulsion is the only option.
In this chapter the matching criteria between combustion engines and ac drives for targeted road load conditions is evaluated. The vehicle power plant is designed to deliver sufficient propulsion power to the driven wheels to meet performance targets that are consistent with vehicle brand image. In the following sections the various trade-offs between power plant torque and power rating are illustrated in regard to transmission selection and vehicle performance.
In this chapter essential guidelines to propulsion power plant sizing are discussed, including the major hybrid components of M/G, power electronics and energy storage system (ESS).
This chapter explores the four classes of electric machines having the most bearing on hybrid propulsion systems: the brushless permanent magnet machine in its surface permanent magnet (SPM) configuration; the interior permanent magnet (IPM) synchronous machine in either inset or buried magnet configuration; the asynchronous or cage rotor induction machine (IM); and lastly, the variable reluctance or doubly salient machine (VRM).
This chapter discusses power electronics for AC drives. Integration of power electronic systems today is at the stage where a single integrated power module consisting of a full active bridge of power semiconductors, integrated gate drivers, and fault detection and reporting logic is available off the shelf.
This chapter gives an assessment of the most popular and relevant control techniques for hybrid propulsion systems. Generally confined to the traction system 'outer-loop', the techniques to be described determine how torque is regulated and speed controlled. Because of the presence of multiple torque sources in the hybrid drivetrain, it is necessary to employ torque control of all the sources, including engine, hybrid M/G(s) and any other source of motive power (flywheels).
This chapter provides an assessment of the complete hybrid drive system and where the prominent loss mechanisms reside. Particular attention is paid to the traction motor generator (M/G) core and copper losses and the inverter conduction and switching losses. Mechanical friction contributions are observed, particularly in regard to nonconventional designs, because of the addition of the hybrid components.
This chapter describes how passenger vehicles are characterised first as to drag and rolling resistance coefficients and second according to fuel economy over standard drive vehicles. Vehicle data necessary to compute rolling resistance and aerodynamic drag coefficients are taken from coast down tests. In this chapter the various standard drive cycles employed in various geographical and demographic areas are compared and rationale given for their selection.
Energy storage systems (ESS) are tailored to the type of fuel being used or to the mechanical, chemical, thermal or electrical form of energy directly stored. Liquid fossil fuels used as feedstock for the engine include gasoline, liquefied petroleum gas (LPG), natural gas (NG) or hydrogen (H2). Mechanical storage systems include flywheels (FW) plus pneumatic (hydraulic) and elastic mediums to store energy in its kinetic and potential energy forms, respectively. Hydraulic storage systems generally use pneumatic means such as a nitrogen bladder as the actual storage medium with the hydraulics as part of the actuation system.
Development of hybrid propulsion systems requires knowledge of the vehicle attributes in terms of mass, frontal area, tyre rolling radius and rolling resistance, plus its aerodynamic drag coefficient. The accepted procedure for obtaining these data comes from vehicle coast down testing. This chapter illustrates the coast down process on two very different vehicles seen often on highways in North America and Europe: the sports utility vehicle (SUV) and tractor-trailers (semis).
A great deal of attention is being paid to more electric vehicles, higher levels of vehicle electrification and also to automated electrified transportation systems. The purpose of this chapter is to shed light on just what automated and electrified transportation is about, who some of the participants are and just how electric power can be transmitted to moving vehicles in order to make all this possible.
For industrial electric machines, prompted by the interest in renewable energy, more energy efficient buildings, products and vehicles in line with objectives of the US Energy Independence and Security Act 2007, a higher level of efficiency is required for 2011 and beyond. Electric machines manufactured after December 2010 will need to comply with the efficiency levels of the energy independence and security act, EISA. In Reference 1, the author states that the average industrial motor consumes electricity worth 50-60 times its initial purchase price over a 10 year lifetime. This means that capital cost is only 2-3% of its lifecycle cost, mainly electricity consumption. Prior to the EISA ruling, an industrial induction motor having an efficiency as targeted by the EPAct is now reclassified as a new subtype I of electric machine, which requires these general purpose motors to now meet the efficiency levels of previous NEMA premium efficiency electric machines. Electric machines for hybrid vehicle application by the very nature of their use demand very high efficiency. In Reference 2, Savagian describes the new electric machine to be used in hybrid electric vehicles and battery electric vehicles that employs copper bar wound stator to realize 30% lower resistance. This electric machine in a BEV drive cycle exhibits 20 οC lower operating temperature than a conventional strand wound electric machine.
