| 1. |
- Kersten, Anton, 1991, et al.
(författare)
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Online and On-Board Battery Impedance Estimation of Battery Cells, Modules or Packs in a Reconfigurable Battery System or Multilevel Inverter
- 2020
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Ingår i: IECON Proceedings (Industrial Electronics Conference). - 2162-4704 .- 2577-1647. ; 2020-October, s. 1884-1891
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Konferensbidrag (refereegranskat)abstract
- This paper shows two approaches to determine the battery impedance of battery cells or battery modules when used in a reconfigurable battery system (RBS) or in any type of modular multilevel converter (MMC) for electric drive applications. A generic battery model is used and the concepts of the recursive time and frequency-domain parameter extraction, using a current step and an electrochemical impedance spectroscopy, are explained. Thus, it is shown and demonstrated that the balancing current of neighboring cells/modules ,when in parallel operation, can be used, similar to the time-domain parameter extraction utilizing a current step, to determine the battery parameters. Furthermore, it is shown and demonstrated that a part of the inverter can be used as variable AC voltage source to control a sinusoidal current through the motor inductances of the drive train, which can be injected to the inserted battery cells/modules of an adjacent phase to perform an on-board impedance spectroscopy. Using either of the two presented approaches, the individual battery impedances can be easily determined, yielding the state of health (SOH) and the power capability of individual battery cells/modules. Nonetheless, the analyzed approaches were just considered to be applied at machine standstill, which is not suitable for grid-tied applications.
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| 2. |
- Han, Weiji, 1987, et al.
(författare)
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Analysis and estimation of the maximum circulating current during the parallel operation of reconfigurable battery systems
- 2020
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Ingår i: 2020 IEEE Transportation Electrification Conference and Expo, ITEC 2020. ; , s. 229-234
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Konferensbidrag (refereegranskat)abstract
- Reconfigurable battery systems (RBSs) are emerging as a promising solution to safe, efficient, and robust energy storage and delivery through dynamically adjusting the battery connection topology. When the system connection is switched from series to parallel, circulating currents between parallel battery cells/modules can be triggered due to their voltage imbalance. During the hardware design of an RBS, the current rating of associated components, such as batteries, switches, and wires, depends on the maximum circulating currents. Moreover, given a developed RBS, the maximum circulating current also determines whether it is feasible to perform the relevant system reconfiguration. Thus, this paper is focused on modeling and analyzing the current distribution during the series-to-parallel battery reconfiguration and estimating the maximum circulating currents as well as their upper bound under various system states and operating scenarios. A prototype is set up to experimentally verify the effectiveness of the proposed method for estimating the maximum circulating currents.
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| 3. |
- Han, Weiji, 1987, et al.
(författare)
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Next-Generation Battery Management Systems: Dynamic Reconfiguration
- 2020
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Ingår i: IEEE Industrial Electronics Magazine. - 1941-0115 .- 1932-4529. ; 14:4, s. 20-31
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Tidskriftsartikel (refereegranskat)abstract
- Batteries are widely applied to the energy storage and power supply in portable electronics, transportation, power systems, communication networks, etc. They are particularly demanded in the emerging technologies of vehicle electrification and renewable energy integration for a green and sustainable society. To meet various voltage, power, and energy requirements in large-scale applications, multiple battery cells have to be connected in series and/or parallel. While battery technology has advanced significantly in the past decade, existing battery management systems (BMSs) mainly focus on state monitoring and control of battery systems packed in fixed configurations. In fixed configurations, though, the battery system performance is in principle limited by the weakest cells, which can leave large parts severely underutilized. Allowing dynamic reconfiguration of battery cells, on the other hand, allows individual and flexible manipulation of the battery system at cell, module, and pack levels, which may open up a new paradigm for battery management. Following this trend, this paper provides an overview of next-generation BMSs featuring dynamic reconfiguration. Motivated by numerous potential benefits of reconfigurable battery systems (RBSs), the hardware designs, management principles, and optimization algorithms for RBSs are sequentially and systematically discussed. Theoretical and practical challenges during the design and implementation of RBSs are highlighted in the end to stimulate future research and development.
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| 4. |
- Kersten, Anton, 1991, et al.
(författare)
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Elimination/Mitigation of Output Voltage Harmonics for Multilevel Converters Operated at Fundamental Switching Frequency using Matlab's Genetic Algorithm Optimization
- 2020
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Ingår i: 2020 22nd European Conference on Power Electronics and Applications, EPE 2020 ECCE Europe. ; , s. 1-12
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the optimization of the output voltage waveform of a multilevel converter operated with fundamental frequency switching. For a high number of output voltage levels, nearest-level control is typically used, whereas an optimized waveform can be presumably used to eliminate a selection of low order harmonics. A nonlinear optimization problem for any kind of multilevel inverter, operating in a single or three-phase arrangement, is formulated. It is shown that the set of nonlinear equations, defining this optimization problem, cannot be numerically solved, if the number of output voltage levels is higher than nine. Thus, an optimization algorithm, e.g., Matlab's genetic algorithm, should be used instead. Based on the concept of the weighted THD, it is shown that an optimized waveform has no effect on the output current's quality of a single phase multilevel converter. However, considering an ungrounded three-phase system, the content of the to be eliminated harmonic components is shifted towards the triplen harmonics and, consequently, the expected current quality, based on the WTHD, can be significantly improved.
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| 5. |
- Kersten, Anton, 1991, et al.
(författare)
-
Output voltage synthesis of a modular battery system based on a cascaded h-bridge multilevel inverter topology for vehicle propulsion: Multilevel pulse width modulation vs. fundamental selective harmonic elimination
- 2020
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Ingår i: 2020 IEEE Transportation Electrification Conference and Expo, ITEC 2020. ; , s. 296-302
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Konferensbidrag (refereegranskat)abstract
- Lately, the research interest for modular battery systems has increased due to the possibility of a better utilization of individual battery packs/cells and the steadily reducing costs of low voltage power electronics. This paper deals with the output voltage synthesis of a modular battery system based on a seven level Cascaded H-bridge (CHB) inverter topology used in a small passenger vehicle. Two methods are considered, Multilevel Pulse Width Modulation (MPWM) and Fundamental Selective Harmonic Elimination (FSHE). Using simulations, the inverter and battery losses, as well as the current THD, are used to assess the effectiveness of both techniques for the broad operating range of a vehicle's drivetrain. It has been shown that FSHE cannot be applied at a modulation index below 0.25, because of the high current THD (> > 5%). Exceeding a modulation index of 0.25, FSHE reduces the battery and inverter losses in comparison to MPWM, while maintaining an acceptable current THD. Operating at higher speeds, FSHE achieves an even better current THD than MPWM. Consequently, it seems reasonable to use a hybrid modulation technique, using MPWM at low and FSHE at higher speeds, respectively. The exact boundary between MPWM and FSHE can vary in accordance with the individual optimization weightings of current THD and drivetrain efficiency.
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| 6. |
- Kersten, Anton, 1991, et al.
(författare)
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Sensorless Capacitor Voltage Balancing of a Grid-Tied, Single-Phase Hybrid Multilevel Converter with Asymmetric Capacitor Voltages using Dynamic Programming
- 2020
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Ingår i: IECON Proceedings (Industrial Electronics Conference). - 2162-4704 .- 2577-1647. ; 2020-October, s. 4288-4293
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Konferensbidrag (refereegranskat)abstract
- This paper shows a sensorless capacitor voltage balancing control approach for a grid-connected, single-phase hybrid multilevel inverter based on an NPC main stage with a voltage stiff DC-link and an arbitrary number of H-Bridge modules (capacitor modules) with asymmetric capacitor voltages. Using nearest-level control, a model predictive control (MPC) approach with a prediction horizon of one time step is chosen to find an optimal switching-state combination among the redundant switching combinations to balance the capacitor voltages as quick as possible. Using the Lyapunov stability criterion, it is shown that an offline calculated optimal switching-state sequence for each discrete output voltage level can be used to operate the inverter without using any voltage sensors for the capacitor voltages. To validate the stability of the approach, a laboratory inverter with a resistive load is operated with the offline calculated optimal switching-state sequences and it is shown that the capacitor voltages converge to their desired reference voltages.
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| 7. |
- Kuder, Manuel, et al.
(författare)
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Battery modular multilevel management (Bm3) converter applied at battery cell level for electric vehicles and energy storages
- 2020
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Ingår i: PCIM Europe Conference Proceedings. - 2191-3358. ; 1, s. 1726-1733
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a modular battery system based on an integrated 3-switch inverter topology, referred to as Battery Modular Multilevel Management (BM3) system. The 3-switch topology can be directly applied on battery cell level. In interconnection with the other battery cells, series and parallel connections can be flexibly formed across the battery modules to synthesize any kind of output voltage. In this manner the BM3 topology can work as a flexible DC/AC or DC/DC converter. Furthermore, individual cells can be bypassed, so that each cell can be charged and drained according to their individual capacity. Thus, any additional passive or active balancing circuitry becomes obsolete. Within the frame of this paper’s analysis, the basic functionality of the BM3 topology is explained and the possible application as a DC/AC inverter is validated using a small scale prototype setup.
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| 8. |
- Theliander, Oskar, et al.
(författare)
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Battery Modeling and Parameter Extraction for Drive Cycle Loss Evaluation of a Modular Battery System for Vehicles Based on a Cascaded H-Bridge Multilevel Inverter
- 2020
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Ingår i: IEEE Transactions on Industry Applications. - 0093-9994 .- 1939-9367. ; 56:6, s. 6968-6977
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Tidskriftsartikel (refereegranskat)abstract
- This article deals with the modeling and the parameterization of the battery packs used in cascaded H-bridge multilevel propulsion inverters. Since the battery packs are intermittently conducting the motor currents, the battery cells are stressed with a dynamic current containing a substantial amount of low-order harmonic components up to a couple of kHz, which is a major difference in comparison to a traditional two-level inverter drive. Different models, such as pure resistive and dynamic RC -networks, are considered to model the energy losses for different operating points (OPs) and driving cycles. Using a small-scale setup, the models’ parameters are extracted using both a low-frequency, pulsed current, and an electrochemical impedance spectroscopy (EIS) sweep. The models are compared against measurements conducted on the small-scale setup at different OPs. Additionally, a drive cycle loss comparison is simulated. The simple resistive model overestimates the losses by about 20% and is, thus, not suitable. The dynamic three-time-constant model, parameterized by a pulsed current, complies with the measurements for all analyzed OPs, especially at low speed, with a maximum deviation of 3.8%. Extracting the parameters using an EIS seems suitable for higher speeds, though the losses for the chosen OPs are underestimated by 1.5%–7.9%.
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