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Previous studies have proposed to use cascaded multilevel topologies in stationary battery energy storage systems (BESSs) or in BESSs of electric vehicles, due to the balancing capability or the high efficiency of these topologies. Because of the elimination of the direct current (DC) bus, the batteries in these topologies are expected to experience large current ripples. However, whether these current ripples can accelerate the aging of the batteries has not yet been dedicatedly investigated, although it is a determining factor for the feasibility of this category of topologies. Therefore, this paper first summarizes the existing studies regarding the influence of current ripples on the aging of lithium batteries, which proves the necessity of an experimental investigation. Then a long-term aging experiment on battery cells is conducted, in order to examine the influence of the current ripples in cascaded multilevel topologies. According to the experimental results and the conclusions in previous studies, the ripples in cascaded multilevel topologies generally have a negligible influence on the aging of batteries, except in certain scenarios. These scenarios can be identified by the three preconditions, first, current ripples must contain micro charge and discharge cycles; second, the micro cycles are below 10 Hz; third, low frequency micro cycles must contribute charge large throughput.
Fengqi Chang; Felix Roemer; Markus Lienkamp. Influence of Current Ripples in Cascaded Multilevel Topologies on the Aging of Lithium Batteries. IEEE Transactions on Power Electronics 2020, 35, 11879 -11890.
AMA StyleFengqi Chang, Felix Roemer, Markus Lienkamp. Influence of Current Ripples in Cascaded Multilevel Topologies on the Aging of Lithium Batteries. IEEE Transactions on Power Electronics. 2020; 35 (11):11879-11890.
Chicago/Turabian StyleFengqi Chang; Felix Roemer; Markus Lienkamp. 2020. "Influence of Current Ripples in Cascaded Multilevel Topologies on the Aging of Lithium Batteries." IEEE Transactions on Power Electronics 35, no. 11: 11879-11890.
This paper presents a method to find the optimal configuration for an electric vehicle energy storage system using a cascaded H-bridge (CHB) inverter. CHB multilevel inverters enable a better utilization of the battery pack, because cells/modules with manufacturing tolerances in terms of capacity can be selectively discharged instead of being passively balanced by discharging them over resistors. The balancing algorithms have been investigated in many studies for the CHB topology. However, it has not yet been investigated to which extend a conventional pack can be modularized in a CHB configuration. Therefore, this paper explores different configurations by simulating different switch models, switch configurations, and number of levels for a CHB inverter along with a reference load model to find the optimal design of the system. The configuration is also considered from an economically point of view, as the most efficient solution might not be cost-effective to be installed in a common production vehicle. It is found that four modules per phase give the best compromise between efficiency and costs. Paralleling smaller switches should be preferred over the usage of fewer, larger switches. Moreover, selecting specific existing components results in higher savings compared to theoretical optimal components.
Felix Roemer; Massab Ahmad; Fengqi Chang; Markus Lienkamp. Optimization of a Cascaded H-Bridge Inverter for Electric Vehicle Applications Including Cost Consideration. Energies 2019, 12, 4272 .
AMA StyleFelix Roemer, Massab Ahmad, Fengqi Chang, Markus Lienkamp. Optimization of a Cascaded H-Bridge Inverter for Electric Vehicle Applications Including Cost Consideration. Energies. 2019; 12 (22):4272.
Chicago/Turabian StyleFelix Roemer; Massab Ahmad; Fengqi Chang; Markus Lienkamp. 2019. "Optimization of a Cascaded H-Bridge Inverter for Electric Vehicle Applications Including Cost Consideration." Energies 12, no. 22: 4272.
There is rapidly growing interest in autonomous electric vehicles due to their potential in improving safety, accessibility, and environmental outcomes. However, their market penetration rate is dependent on costs. Use of autonomous electric vehicles for shared-use mobility may improve their cost competitiveness. So far, most of the research has focused on the cost impact of autonomy on taxis and ridesourcing services. Singapore is planning for island-wide deployment of autonomous vehicles for both scheduled and on-demand services as part of their transit system in the year 2030. TUMCREATE developed an autonomous electric vehicle concept, a microtransit vehicle with 30-passenger capacity, which can complement the existing bus transit system. This study aims to determine the cost of autonomous electric microtransit vehicles and compare them to those of buses. A total cost of ownership (TCO) approach was used to compare the lifecycle costs. It was shown that although the acquisition costs of autonomous electric vehicles are higher than those of their conventional counterparts, they can reduce the TCO per passenger-km up to 75% and 60% compared to their conventional counterparts and buses, respectively.
Aybike Ongel; Erik Loewer; Felix Roemer; Ganesh Sethuraman; Fengqi Chang; Markus Lienkamp. Economic Assessment of Autonomous Electric Microtransit Vehicles. Sustainability 2019, 11, 648 .
AMA StyleAybike Ongel, Erik Loewer, Felix Roemer, Ganesh Sethuraman, Fengqi Chang, Markus Lienkamp. Economic Assessment of Autonomous Electric Microtransit Vehicles. Sustainability. 2019; 11 (3):648.
Chicago/Turabian StyleAybike Ongel; Erik Loewer; Felix Roemer; Ganesh Sethuraman; Fengqi Chang; Markus Lienkamp. 2019. "Economic Assessment of Autonomous Electric Microtransit Vehicles." Sustainability 11, no. 3: 648.
Public transportation (PT) systems suffer from disutility compared to private transportation due to the inability to provide passengers with a door-to-door service, referred to as the first/last mile problem. Personal mobility devices (PMDs) are thought to improve PT service quality by closing this first/last mile gap. However, current PMDs are generally driven manually by the rider and require a learning phase for safe vehicle operation. Additionally, most PMDs require a standing riding position and are not easily accessible to elderly people or persons with disabilities. In this paper, the concept of an autonomously operating mobility device is introduced. The visionary concept is designed as an on-demand transportation service which transports people for short to medium distances and increases the accessibility to public transport. The device is envisioned to be operated as a larger fleet and does not belong to an individual person. The vehicle features an electric powertrain and a one-axle self-balancing design with a small footprint. It provides one seat for a passenger and a tilt mechanism that is designed to improve the ride comfort and safety at horizontal curves. An affordable 3D-camera system is used for autonomous localization and navigation. For the evaluation and demonstration of the concept, a functional prototype is implemented.
Manfred Klöppel; Felix Römer; Michael Wittmann; Bijan Hatam; Thomas Herrmann; Lee Leng Sim; Jun Siang Douglas Lim; Yunfan Lu; Vladimir Medovy; Lukas Merkle; Wy Xin Richmond Ten; Aybike Ongel; Yan Jack Jeffrey Hong; Heong Wah Ng; Markus Lienkamp. Scube—Concept and Implementation of a Self-balancing, Autonomous Mobility Device for Personal Transport. World Electric Vehicle Journal 2018, 9, 48 .
AMA StyleManfred Klöppel, Felix Römer, Michael Wittmann, Bijan Hatam, Thomas Herrmann, Lee Leng Sim, Jun Siang Douglas Lim, Yunfan Lu, Vladimir Medovy, Lukas Merkle, Wy Xin Richmond Ten, Aybike Ongel, Yan Jack Jeffrey Hong, Heong Wah Ng, Markus Lienkamp. Scube—Concept and Implementation of a Self-balancing, Autonomous Mobility Device for Personal Transport. World Electric Vehicle Journal. 2018; 9 (4):48.
Chicago/Turabian StyleManfred Klöppel; Felix Römer; Michael Wittmann; Bijan Hatam; Thomas Herrmann; Lee Leng Sim; Jun Siang Douglas Lim; Yunfan Lu; Vladimir Medovy; Lukas Merkle; Wy Xin Richmond Ten; Aybike Ongel; Yan Jack Jeffrey Hong; Heong Wah Ng; Markus Lienkamp. 2018. "Scube—Concept and Implementation of a Self-balancing, Autonomous Mobility Device for Personal Transport." World Electric Vehicle Journal 9, no. 4: 48.
While an increasing number of electric bicycles are sold, the majority is still conventional, i.e., pedal powered.Electric bicycles could raise the share of people cycling in place of more inefficient modes of transportation. This paper investigates and proposes a new approach for an electric drive unit that can easily be attached and detached to a large majority of existing off-the-shelf bicycles to convert them into legal electric assisted bicycles (pedelecs). Different drive mechanisms were investigated and a design with a friction roller at the rear wheel showed the greatest potential. A good solution is achieved with a single unit that incorporates batteries, electronics, motors and sensors in a single enclosure to minimize the mounting time. With a fastening on the seat stay tube using a simple clamp mechanism it can assist the cyclist on most existing bicycles. The legally-required pedal detection is done with an integrated proximity sensor. A prototype is built to prove a simple and nonspecific installation and convenient usage.
Felix Roemer; Marius Mrosek; Simon Schmalfuss; Markus Lienkamp. New Approach for an Easily Detachable Electric Drive Unit for Off-the-Shelf Bicycles. World Electric Vehicle Journal 2018, 9, 37 .
AMA StyleFelix Roemer, Marius Mrosek, Simon Schmalfuss, Markus Lienkamp. New Approach for an Easily Detachable Electric Drive Unit for Off-the-Shelf Bicycles. World Electric Vehicle Journal. 2018; 9 (3):37.
Chicago/Turabian StyleFelix Roemer; Marius Mrosek; Simon Schmalfuss; Markus Lienkamp. 2018. "New Approach for an Easily Detachable Electric Drive Unit for Off-the-Shelf Bicycles." World Electric Vehicle Journal 9, no. 3: 37.
To better evaluate the configuration of battery packs in electric vehicles (EV) in the early design phase, this paper proposes a mathematic model for the simulation of battery packs based on the elementwise calculations of matrices. This model is compatible with the different battery models and has a fast simulation speed. An experimental platform is built for the verification. Based on the proposed model and the statistic features of battery cells, the influence of the number of paralleled cells in a battery pack is evaluated in Monte-Carlo experiments. The simulation results obtained from Monte-Carlo experiments show that the parallel number is able to influence the total energy loss inside the cells, the energy loss caused by the balancing of the battery management system (BMS) and the degradation of the battery pack.
Fengqi Chang; Felix Roemer; Michael Baumann; Markus Lienkamp. Modelling and Evaluation of Battery Packs with Different Numbers of Paralleled Cells. World Electric Vehicle Journal 2018, 9, 8 .
AMA StyleFengqi Chang, Felix Roemer, Michael Baumann, Markus Lienkamp. Modelling and Evaluation of Battery Packs with Different Numbers of Paralleled Cells. World Electric Vehicle Journal. 2018; 9 (1):8.
Chicago/Turabian StyleFengqi Chang; Felix Roemer; Michael Baumann; Markus Lienkamp. 2018. "Modelling and Evaluation of Battery Packs with Different Numbers of Paralleled Cells." World Electric Vehicle Journal 9, no. 1: 8.
In the CAN bus standard every node has a defined and fixed ID and it is not intended that there is a flexible replacement and exchange necessary. However, for certain use cases a CAN bus with such a functionality can be required. In the said cases a self-assignment can be mandatory to avoid double IDs, but without a master controller or additional communication interfaces it is challenging to ensure compatibility. For example, if there are several identical battery modules that have to be replaced regularly or with varying applications like second-life usage, such a solution can be used. Therefore, this paper proposes the idea of a random self-assignment with very defined handling of how it can be ensured and checked that no ID is assigned twice and what to do if that happened. This solution has been implemented as a demonstrator and tested thoroughly including special cases with enforced errors.
Felix Roemer; Matthias Lamparter; Markus Lienkamp. A method for masterless self-assigning CAN bus identifier. 2017 IEEE Transportation Electrification Conference and Expo (ITEC) 2017, 119 -123.
AMA StyleFelix Roemer, Matthias Lamparter, Markus Lienkamp. A method for masterless self-assigning CAN bus identifier. 2017 IEEE Transportation Electrification Conference and Expo (ITEC). 2017; ():119-123.
Chicago/Turabian StyleFelix Roemer; Matthias Lamparter; Markus Lienkamp. 2017. "A method for masterless self-assigning CAN bus identifier." 2017 IEEE Transportation Electrification Conference and Expo (ITEC) , no. : 119-123.