| 1. |
- Altaf, Faisal, 1982, et al.
(author)
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Feasibility Issues of using Three-Phase Multilevel Converter based Cell Balancer in Battery Management System for xEVs
- 2013
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In: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902823434 ; 46, s. 390-397
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Conference paper (peer-reviewed)abstract
- The use of a three-phase multilevel converter (MLC) as an integrated cell balancer and motor driver is investigated for three-phase AC applications in EVs/HEVs/PHEVs. The paper analyzed an issue of additional battery losses caused by the flow of reactive and/or harmonic power from each power cell of the three-phase MLC battery system. The paper also investigates the size of shunt capacitor required for compensation of the losses to acceptable level. This study concludes that the size of the required capacitor is too big for the vehicle application unless some other active compensation is used as well. Another practical way to employ the MLC as a cell balancer is to use it in a cascaded connection with the conventional three-phase two-level voltage source inverter however it may not be a cost-effective solution either due to high component count.
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| 2. |
- Egardt, Bo, 1950, et al.
(author)
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Electromobility Studies Based on Convex Optimization DESIGN AND CONTROL ISSUES REGARDING VEHICLE ELECTRIFICATION
- 2014
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In: IEEE Control Systems. - 1066-033X. ; 34:2, s. 32-49
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Journal article (peer-reviewed)abstract
- This article presents a framework to study design tradeoffsin the search for electromobility solutions based on approximatemodeling of the power flows in the powertrain as afunction of component sizes. An important consequence ofthe modeling assumptions is that the optimal energy managementand component sizes can be computed simultaneouslyin a convex program, which means that competingdesigns can be evaluated in an objective way, avoiding theinfluence of a separate control system design. The fact thatthe optimization problem is convex allows large problemsto be solved with moderate computational resources, whichcan be exploited by, for example, running optimizationsover very long driving cycles. The problem formulationalso admits design decisions for the charging infrastructureto be included in the optimization.
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| 3. |
- Hu, Xiaosong, 1983, et al.
(author)
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Comparison of Three Electrochemical Energy Buffers Applied to a Hybrid Bus Powertrain with Simultaneous Optimal Sizing and Energy Management
- 2014
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In: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 15:3, s. 1193-1205
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Journal article (peer-reviewed)abstract
- This paper comparatively examines three different electrochemical energy storage systems (ESSs), i.e., Li-ion battery, supercapacitor, and dual buffer, for a hybrid bus powertrain operated in Gothenburg, Sweden. Existing studies focus on comparing these ESSs in terms of either general attributes (e.g., energy density and power density) or their implications to the fuel economy of hybrid vehicle with a heuristic/non-optimal ESS size and power management strategy. This paper adds four original contributions to the related literature. First, the three ESSs are compared in a framework of simultaneous optimal ESS sizing and energy management, where the ESSs can serve the powertrain in a most cost-effective manner. Second, convex optimization is used to implement the framework, which allows the hybrid powertrain designers/integrators to rapidly and optimally perform integrated ESS selection, sizing, and power management. Third, both hybrid electric vehicle (HEV) and plug-in hybrid electric vehicle (PHEV) scenarios for the powertrain are considered, in order to systematically examine how different the ESS requirements are for HEV and PHEV applications. Finally, a sensitivity analysis is carried out to evaluate how price variations of the on-board energy carriers affect the results and conclusions.
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| 4. |
- Hu, Xiaosong, 1983, et al.
(author)
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Energy efficiency analysis of a series plug-in hybrid electric bus with different energy management strategies and battery sizes
- 2013
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 111, s. 1001-1009
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Journal article (peer-reviewed)abstract
- This paper is concerned with the tank-to-wheel (TTW) analysis of a series plug-in hybrid electric bus operated in Gothenburg, Sweden. The bus line and the powertrain model are described. The definition and the calculation method of the recuperation and fuel-to-traction efficiencies are delineated for evaluating the TTW energy conversion. The two efficiencies are quantified and compared for two optimization-based energy management strategies, in which convex modeling and optimization are used. The impact of downsizing the battery on the two efficiencies is also investigated.
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| 5. |
- Hu, Xiaosong, 1983, et al.
(author)
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Longevity-conscious dimensioning and power management of the hybrid energy storage system in a fuel cell hybrid electric bus
- 2015
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 137, s. 913-
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Journal article (peer-reviewed)abstract
- Energy storage systems (ESSs) play an important role in the performance and economy of electrified vehicles. Hybrid energy storage system (HESS) combining both lithium-ion cells and supercapacitors is one of the most promising solutions. This paper discusses the optimal HESS dimensioning and energy management of a fuel cell hybrid electric bus. Three novel contributions are added to the relevant literature. First, efficient convex programming is used to simultaneously optimize the HESS dimension (including sizes of both the lithium-ion battery pack and the supercapacitor stack) and the power allocation between the HESS and the fuel cell system (FCS) of the hybrid bus. In the combined plant/controller optimization problem, a dynamic battery State-of-Health (SOH) model is integrated to quantitatively examine the impact of the battery replacement strategy on both the HESS size and the bus economy. Second, the HESS and the battery-only ESS options are systematically compared in the proposed optimization framework. Finally, the battery-health-perceptive HESS optimization outcome is contrasted to the ideal one neglecting the battery degradation (assuming that the battery is durable over the bus service period without deliberate power regulation).
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| 6. |
- Hu, Xiaosong, 1983, et al.
(author)
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Optimal Dimensioning and Power Management of a Fuel Cell/Battery Hybrid Bus via Convex Programming
- 2015
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In: IEEE/ASME Transactions on Mechatronics. - 1083-4435 .- 1941-014X. ; 20:1, s. 457-468
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Journal article (peer-reviewed)abstract
- This paper is concerned with the simultaneous optimal component sizing and power management of a fuel cell/battery hybrid bus. Existing studies solve the combined plant/controller optimization problem for fuel cell hybrid vehicles (FCHVs) by using methods with disadvantages of heavy computational burden and/or suboptimality, for which only a single driving profile was often considered. This paper adds three important contributions to the FCHVs-related literature. First, convex programming is extended to rapidly and efficiently optimize both the power management strategy and sizes of the fuel cell system (FCS) and the battery pack in the hybrid bus. The main purpose is to encourage more researchers and engineers in FCHVs field to utilize the new effective tool. Second, the influence of the driving pattern on the optimization result (both the component sizes and hydrogen economy) of the bus is systematically investigated by considering three different bus driving routes, including two standard testing cycles and a realistic bus line cycle with slope information in Gothenburg, Sweden. Finally, the sensitivity of the optimization outcome to the potential price decreases of the FCS and the battery is quantitatively examined.
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| 7. |
- Johannesson, Lars, 1979, et al.
(author)
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Including a battery state of health model in the hev component sizing and optimal control problem
- 2013
-
In: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823434 ; , s. 398-403
-
Conference paper (peer-reviewed)abstract
- This paper studies convex optimization and modelling for component sizing and optimal energy management control of hybrid electric vehicles. The novelty in the paper is the modeling steps required to include a battery wear model into the convex optimization problem. The convex modeling steps are described for the example of battery sizing and simultaneous optimal control of a series hybrid electric bus driving along a perfectly known bus line. Using the proposed convex optimization method and battery wear model, the city bus example is used to study a relevant question: is it better to choose one large battery that is sized to survive the entire lifespan of the bus, or is it beneficial with several smaller replaceable batteries which could be operated at higher c-rates?
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| 8. |
- Johannesson, Lars, 1979, et al.
(author)
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Look-ahead Vehicle Energy Management with Traffic Predictions
- 2015
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In: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 48:15, s. 244-251
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Journal article (peer-reviewed)abstract
- This paper presents a vehicle energy management system that uses information about upcoming topography and speed limits along the planned route to schedule the speed and the gear shifts of a heavy diesel truck. The proposed control scheme divides the predictive control problem into two layers that operate with different update frequencies and prediction horizons. The focus in the paper is on the top layer that plans the vehicle speed in a convex optimization problem leaving the gear decision to be optimized in the lower layer in a dynamic program. The paper describes how predictive information of the movement pattern of surrounding vehicles can be incorporated into the convex optimization of the vehicle speed by using a moving time window constraint.
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| 9. |
- Johannesson, Lars, 1979, et al.
(author)
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Predictive energy management of hybrid long-haul trucks
- 2015
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In: Control Engineering Practice. - : Elsevier Ltd. - 0967-0661 .- 1873-6939. ; 41, s. 83-97
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Journal article (peer-reviewed)abstract
- This paper presents a novel predictive control scheme for energy management in hybrid trucks that drive autonomously on the highway. The proposed scheme uses information from GPS together with information about the speed limits along the planned route to schedule the charging and discharging of the battery, the vehicle speed, the gear, and when to turn off the engine and drive electrically. The proposed control scheme divides the predictive control problem into three layers that operate with different update frequencies and prediction horizons. The top layer plans the kinetic and electric energy in a convex optimization problem. In order to avoid a mixed-integer problem, the gear and the switching decision between hybrid and pure electric mode are optimized in a lower layer in a dynamic program whereas the lowest control layer only reacts on the current state and available references. The benefits of the proposed predictive control scheme are shown by simulations between Frankfurt and Koblenz. The simulations show that the predictive control scheme is able to significantly reduce the mechanical braking, resulting in fuel reductions of 4% when allowing an over and under speed of 5. km/h
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| 10. |
- Larsson, Viktor, 1984, et al.
(author)
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Analytic Solutions to the Dynamic Programming sub-problem in Hybrid Vehicle Energy Management
- 2015
-
In: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 64:4, s. 1458-1467
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Journal article (peer-reviewed)abstract
- The computationally demanding Dynamic Programming(DP) algorithm is frequently used in academic research tosolve the energy management problem of an Hybrid ElectricVehicle (HEV). This paper is focused exclusively on how thecomputational demand of such a computation can be reduced.The main idea is to use a local approximation of the griddedcost-to-go and derive an analytic solution for the optimal torquesplit decision at each point in the time and state grid. Therebyit is not necessary to quantize the torque split and identifythe optimal decision by interpolating in the cost-to-go. Twodifferent approximations of the cost-to-go are considered in thepaper: i) a local linear approximation, and ii) a quadratic splineapproximation. The results indicate that computation time can bereduced by orders of magnitude with only a slight degradation insimulated fuel economy. Furthermore, with a spline approximatedcost-to-go it is also possible to significantly reduce the memorystorage requirements. A parallel Plug-in HEV is considered inthe paper but the method is also applicable to an HEV.
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