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While the ZEV program's electric vehicles did not become successful market-driven products, many of the technical advantages of electric vehicles were validated by enthusiastic California consumers. Yet, battery technology has been and continues to be the limiting factor in terms of cost, functionality (range) and durability of EV systems. The automotive industry has largely moved on to research and development of other approaches to extremely low emissions and reduced fossil fuel consumption. PZEV gasoline vehicles, Hybrid electric vehicles, clean (EPA Tier 2) diesel vehicles and Proton Exchange Membrane (PEM) fuel cell electric vehicles (FCEVs) are the focus of attention. The purpose of this paper is to explore another possible solution: a battery electric vehicle with a relatively small fuel cell auxiliary power unit (APU) to recharge the battery pack during driving.

Delphi and the National Renewable Energy Laboratory (NREL) collaborated to develop a simulation code to model the mechanical and electrical architectures of a series hybrid vehicle simultaneously. This co-simulation code is part of the larger ADVISOR® product created by NREL and diverse partners. Simulation of the macro power flow in a series hybrid vehicle requires both the mechanical drivetrain and the entire electrical architecture. It is desirable to solve the electrical network equations in an environment designed to comprehend such a network and solve the equations in terms of current and voltage. The electrical architecture for the series hybrid vehicle has been modeled in Saber™ to achieve these goals. This electrical architecture includes not only the high-voltage battery, generator, and traction motor, but also the normal low-voltage bus (14V) with loads common to all vehicles.

The purpose of this paper is to demonstrate how simulation can impact the design process for an integrated starter generator (ISG) vehicle. Many aspects of the ISG system from the sizing of the electrical machine, the sizing of the battery(ies), the choice of battery chemistry, the choice of voltage, and the choice of control algorithms can be simulated with minimal expense or time consumption. Such simulations can assist the engineering team in making optimal design choices, all in advance of committing any expenditure of prototype funding. Simulations can provide an accurate approximation to the actual fuel economy impact of each of the potential higher-voltage functionalities that come with an ISG system. Further, total vehicle performance can be simulated to determine any performance-related issues prior to prototype component design and build. Content will be pulled from other papers to address the session topic of simulation impact on ISG vehicle design.

North American sales of light duty trucks, including sport utility vehicles (SUV's), have now passed the 50% mark of total vehicles sold. This fact, along with the recent surge in gas prices, has drawn attention to the lower average fuel economy of this vehicle class. With possible changes to the light duty truck corporate average fuel economy (CAFE) standards looming on the horizon, vehicle manufacturers are looking for ways to improve the fuel economy of these vehicles without affecting performance or utility. One possible solution in accomplishing this objective is the 42 volt integrated starter-generator (ISG). The ISG offers the ability to reduce fuel consumption through the use of engine-off during coast-down and idle, early torque converter lockup with torque smoothing, regenerative braking, and electrical launch assist. It also boosts the onboard power generation and energy storage, allowing for increased vehicle electrical loads.

One of the challenges of analyzing vehicular electrical systems is the co-dependence of the electrical system and the propulsion system. Even in traditional vehicles where the electrical power budget is very low, the electrical system analysis for macro power utilization over a drive cycle requires knowledge of the generator shaft rpm profile during the drive cycle. This co-dependence increases as the electrical power budget increases, and the integration of the two systems becomes complete when hybridization is chosen. Last year at this conference, the authors presented a paper entitled “Dual Voltage Electrical System Simulations.” That paper established validation for a suite of electrical component models and demonstrated the ability to predict system performance both on a macro power flow (entire drive cycle) level and a detailed transient-event level. The techniques were applicable to 12V, 42V, dual voltage, and/or elevated voltage systems.

A recent SAE paper entitled “Automotive Electrical Systems: Architecture and Components” by Iftikar Khan1 explored many potential electrical hardware and architectural issues for future vehicles. For these concepts to become viable in the marketplace, effective and competitive engineering practice requires that the design and trade studies be performed in the virtual world with hardware prototype validating the design rather than traditional build / break design cycles. This paper studies simulation requirements for such systems including component technical requirements and ease of calibration to specific hardware and proposed designs. This paper will demonstrate modeling techniques for generators (averaged, 3 phase, 14V, and 42V), DC to DC converters, lead acid batteries, and lithium polymer batteries. The viability of the methods will be demonstrated and validated at the component level.