On Discharge Strategies for Plug-in Hybrid Electric Vehicles

• During recent years electrification of vehicles has emerged as a promisingtechnology to reduce oil dependency and CO2 emissions within the transportationsector. At the present day several automotive manufacturers areabout to introduce plug-in hybrid electric vehicles to the market, i.e. hybridelectric vehicles with high capacity batteries that are grid rechargeable.As with most new technologies this introduces new control problems to besolved by engineers and researchers.This thesis investigates one of these new control problems, namely howto optimally discharge the battery of a plug-in hybrid electric vehicle ontrips that exceed the electric range. Rather than using the trivial dischargestrategy, which is to operate as an electric vehicle until the battery is depletedand then proceed in charge sustaining operation as a conventionalhybrid electric vehicle, it is possible to improve powertrain efficiency if thebattery is discharged gradually throughout the trip. A gradual dischargelowers the average discharge current, thereby lowering the resistive lossesthat are quadratic in current. However, to find a suitable discharge ratesome a priori information regarding the future trip is required.In the thesis it is shown that the a priori information needed can beobtained using route recognition; an algorithm with low computational demandis proposed and evaluated using simulations on logged commuter drivingdata. The results suggest that notable fuel cost reductions are possiblefor commuters that frequently drive along routes that exceed the electricrange. Furthermore, the impact of trip length uncertainty on the optimaldischarge rate is also studied and results indicate that it is preferable tounderestimate rather than overestimate the trip length. A separate investigationconcludes that uncertain estimates of the battery state of chargeonly has minor effects on the optimal discharge rate.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Reglerteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Control Engineering (hsv//eng)

Nyckelord

Route Recognition

Energy Management

Dynamic Programming

Hybrid Electric Vehicles

Plug-in Hybrid Electric Vehicles

Publikations- och innehållstyp

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