This review is dedicated to balancing methods that are used to solve the rotor-balancing problem. To ensure a stable operation over an operating speed range, it is necessary to balance a rotor. The ...traditional methods, including the influence coefficient method (ICM) and the modal balancing method (MBM) are introduced, and the research progress, operation steps, advantages and disadvantages of these methods are elaborated. The classification of new balancing methods is reviewed. Readers are expected to obtain an overview of the research progress of existing balancing methods and the directions for future studies.
Covariate balance is crucial for unconfounded descriptive or causal comparisons. However, lack of balance is common in observational studies. This article considers weighting strategies for balancing ...covariates. We define a general class of weights-the balancing weights-that balance the weighted distributions of the covariates between treatment groups. These weights incorporate the propensity score to weight each group to an analyst-selected target population. This class unifies existing weighting methods, including commonly used weights such as inverse-probability weights as special cases. General large-sample results on nonparametric estimation based on these weights are derived. We further propose a new weighting scheme, the overlap weights, in which each unit's weight is proportional to the probability of that unit being assigned to the opposite group. The overlap weights are bounded, and minimize the asymptotic variance of the weighted average treatment effect among the class of balancing weights. The overlap weights also possess a desirable small-sample exact balance property, based on which we propose a new method that achieves exact balance for means of any selected set of covariates. Two applications illustrate these methods and compare them with other approaches.
This book is a collection of scientific papers concerning multilevel inverters examined from different points of view. Many applications are considered, such as renewable energy interface, power ...conditioning systems, electric drives, and chargers for electric vehicles. Different topologies have been examined in both new configurations and well-established structures, introducing novel and particular modulation strategies, and examining the effect of modulation techniques on voltage and current harmonics and the total harmonic distortion.
This letter presents a compact switched capacitor multilevel inverter (CSCMLI) topology with reduced switch count and with self-voltage balancing and boosting ability. The operational mode of the ...proposed CSCMLI is discussed. A comparative analysis in terms of number of switches and blocking voltages is presented against recent switched capacitor multilevel inverter topologies. Further to enhance the quality of the output voltage, a new level shifted multicarrier pulsewidth modulation (PWM) technique is recommended. This modulation technique produces low THD and high rms voltage. The proposed modulation technique is implemented in the nine-level CSCMLI with single dc source and two capacitors. The simulated and experimental results are verified for a switching frequency of 50 Hz and 2.5 kHz using the proposed PWM control.
Im Rahmen eines von der Gesellschaft für Energie und Klimaschutz Schleswig‐Holstein GmbH (EKSH) geförderten Forschungsvorhabens wurden CO2‐Blanzierungen an insgesamt 34 realen und mehreren Hundert ...generierten Brückenbauwerken durchgeführt. Zielsetzung war es, Erfahrungswerte zu erarbeiten, bei welchen Brückenkonstruktionen wie viel CO2 emittiert wird, und Vorschläge auszuarbeiten, wie sich die CO2‐Emissionen reduzieren lassen.
Translation
CO2 balancing of bridges with structure lengths up to 40 m
As part of a research project, funded by the Gesellschaft für Energie und Klimaschutz Schleswig‐Holstein GmbH (EKSH), CO2 balancing was carried out on a total of 34 real and several hundred generated bridge constructions. The objectives were to develop empirical data, how much CO2 bridge constructions emit and to develop suggestions on how CO2 emissions can be reduced.
Recently, deep-learning methods have been successfully applied to the ship detection in the synthetic aperture radar (SAR) images. It is still a great challenge to detect multiscale SAR ships due to ...the broad diversity of the scales and the strong interference of the inshore background. Most prevalent approaches are based on the anchor mechanism that uses the predefined anchors to search the possible regions containing objects. However, the anchor settings have a great impact on their detection performance as well as the generalization ability. Furthermore, considering the sparsity of the ships, most anchors are redundant and will lead to the computation increase. In this article, a novel detection method named feature balancing and refinement network (FBR-Net) is proposed. First, our method eliminates the effect of anchors by adopting a general anchor-free strategy that directly learns the encoded bounding boxes. Second, we leverage the proposed attention-guided balanced pyramid to balance semantically the multiple features across different levels. It can help the detector learn more information about the small-scale ships in complex scenes. Third, considering the SAR imaging mechanism, the interference near the ship boundary with the similar scattering power probably affects the localization accuracy because of feature misalignment. To tackle the localization issue, a feature-refinement module is proposed to refine the object features and guide the semantic enhancement. Finally, extensive experiments are conducted to show the effectiveness of our FBR-Net compared with the general anchor-free baseline. The detection results on the SAR ship detection dataset (SSDD) and AIR-SARShip-1.0 dataset illustrate that our method achieves the state-of-the-art performance.
This paper addresses a two-stage module based cell-to-cell active equalization topology based on a modified buck-boost converter for series connected Lithium-ion battery packs. In the proposed ...topology, initially module based equalizing currents are controlled. Subsequently, cell-based equalizers are controlled in parallel within each battery module. The proposed topology significantly reduces the balancing time by transferring higher balancing current from a strong cell to the weakest cell in a module directly. With the proposed topology's modularized design, reduces voltage stress on long strings of switches, resulting in improved performance with fewer components. The operating principle, control strategy and design constraints are analyzed in detail. The MATLAB/Simulink platform is utilized to demonstrate the feasibility of the proposed technique for balancing the energy in series connected battery cells. To reduce the complexity of the control approach, the digital control is implemented using an FPGA control board. Further, a laboratory prototype is developed to show the feasibility and operability of the proposed topology.
In this article, an improved dc capacitor voltage balancing control is proposed for single-phase cascaded H-bridge (CHB) multilevel converters. Compared with conventional voltage balancing control ...methods, the proposed scheme has a comprehensive consideration of three aspects while balancing the capacitor voltages among H-bridges: coupling effect elimination, reactive power balancing, and dynamic performance improvement. First, the system mathematical model in the d-q reference frame is derived, and the relationship among duty cycle modifications of H-bridges is revealed to eliminate the coupling effect of voltage balancing control on the current control loop. Then, based on the H-bridge power model, a quantitative solution for reactive power balancing is presented to design the reactive duty cycle modifications. In order to enhance the dynamic performance of voltage balancing control, a dynamic references design method is adopted to evaluate the active duty cycle modifications. Finally, both simulation and experimental results are presented to validate the effectiveness of the proposed scheme.
This article explores a single-source UXE-type asymmetrical multilevel inverter for its operation on 13-, 11-, and 9-levels with boosted output voltage. The 13- and 11-level operations require a ...single voltage sensor to maintain the auxiliary dc link at <inline-formula><tex-math notation="LaTeX">V_{\text{dc}}/2</tex-math></inline-formula> and produce 1.5 and 1.25 boosting using redundant states and exhibit lower capacitor inrush currents. For the 9-level operation, the topology exhibits self-balancing of the dc-link at <inline-formula><tex-math notation="LaTeX">V_{\text{dc}}</tex-math></inline-formula> and a boosting of 2. With a conventional pulsewidth modulation (PWM) for the 13-level operation, the inverter can drive a predominantly inductive load of 0.35 lagging at unity modulation index. For the 11-level operation, the levels cease to maintain beyond the modulation of 0.95. Thus, a hybrid PWM is proposed to fully utilize the redundant states for the charging of the switched-capacitors and enhance the inverter active load capability in the 13-level mode by 21% at unity modulation index (<inline-formula><tex-math notation="LaTeX">m_a</tex-math></inline-formula>) and address a 0.8 power factor load at the <inline-formula><tex-math notation="LaTeX">m_a</tex-math></inline-formula> of 0.9. For the 11-level operation, the levels are maintained at any <inline-formula><tex-math notation="LaTeX">m_a</tex-math></inline-formula> with the hybrid PWM. The operation of the inverter is also verified for nonlinear load. Further, the 9-level operation with twice boosting and self-balancing is presented. The results are verified on MATLAB/Simulink and validated experimentally.
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