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This study investigates the impact of different levels of modeling details on the problem of optimizing the total cost of ownership of a fuel-cell hybrid electric vehicle. In this optimization, the objective function is a weighted sum of operational and component costs over a driving cycle. The former includes the consumed hydrogen and electrical energy, and the latter includes the sum of the battery, fuel-cell, and electric-motor costs. Three methods with different levels of modelling details are investigated; in the first method, the power split between the two power sources together with component sizes are optimized, while assuming nonlinear loss functions for the components. In the second method, the efficiencies of the components are approximated by constant values. In the third method, the problem is simplified further by considering the energy split between the battery and the fuel-cell. As shown in the results, a more detailed model gives more accurate results at the price of increased computation time. However, the simplified models can give similar results as the detailed model in most cases. In some problems though, the model simplifications lead to results that differ notably from those obtained by using the detailed model. [ABSTRACT FROM AUTHOR]

This paper introduces a novel method for the simultaneous optimization of energy management and powertrain component sizing of a parallel plug-in hybrid electric vehicle (PHEV). The problem is formulated as a convex optimization problem to minimize an objective function, which is a weighted sum of operational and component costs. The operational cost includes the consumed fossil fuel and electrical energy, whereas the component cost includes the cost of the battery, electric motor (EM), and internal combustion engine (ICE). The powertrain model includes quadratic losses for the powertrain components. Moreover, the combustion engine and the electric motor losses are assumed to linearly scale with respect to the size and the losses of baseline components. The result of the optimization is the variables of the global optimal energy management for every time instant and optimal component sizes. Due to the dependency of the result on the driving cycle, a long real-life cycle with its charging times is chosen to represent a general driving pattern. The method allows the study of the effect of some performance requirements, i.e., acceleration, top speed, and all-electric range, on the component sizes and total cost. [ABSTRACT FROM PUBLISHER]

This paper discusses the practical limits imposed by magnetic saturation for the force density in low-speed permanent- magnet electric machines. The force density dependence on current density and slot depth is investigated with the aid of finite-element modeling. For saturation reasons, shallow slots are more favorable for achieving high force densities. However, for thermal reasons, deeper slots become favorable. Therefore, an optimum slot depth that maximizes the force density for each current density level exists. The maximum allowable slot depth range for four low-speed applications has been identified for a given maximum motor diameter. [ABSTRACT FROM AUTHOR]

This paper discusses two of the mechanisms that limit the attainable force density in slotted low-speed permanent-magnet (PM) electric machines. Most of the interest is focused on the force density limits imposed by heating of the windings and by stator reactance. The study is based on analytical models for the force and reactance calculations and a lumped parameter thermal model. It is found that in a machine with an indirectly cooled stator, it is difficult to achieve a force density greater than 100 kN/m2 due to temperature limits. A high force density Is achieved by using deep slots, which lead to high reactance. The high reactance severely increases the converter kilovolt-ampere requirement and total system cost. It is also shown that the cost caused by the high reactance will also limit the force density reached. In machines with one slot per pole per phase, the reactance limited the useful slot depth to approximately 200 mm. However, in machines having a greater number of slots per pole per phase the reactance becomes no longer an Important limiting factor for the slot depth and force density. [ABSTRACT FROM AUTHOR]

Describes a method to calculate the average efficiency from the turbine shaft to the grid in wind energy converters. Comparison of the average efficiency of three generator systems; Variable-speed generator system; Directly-driven generator; Conventional four-pole generator equipped with a gear.