Series-connected lithium battery packs are widely adopted in industries such as electrical vehicles and large-scale energy storage systems. It is necessary to configure an equalization system for them to reduce the inconsistency of single cells, to ensure the battery pack cycle capacity. Although many novel active converters have been proposed for equalization, there still lacks systematic analyses on variables, topologies, and modular methods. Therefore, this paper provides a systematic review on the above aspects. Initially, an overall summary is present on current variables for equalization control. Second, the dominant structures are divided into cell-to-cell, cell-to-pack, and pack-to-pack topologies, and their characteristics are pointed out for comparison. And then, the modular methods, including single-layer-based, multi-layer-based, and hybrid integrations are evaluated via graph theory. Some key issues and potential research directions are given, which are expected to offer assistance on the selection of appropriate variables and topologies for equalization systems in the future.
To improve the dynamic response of the inverter, the conventional proportional-integral controller and the modulation part are substituted by the finite-control step model predictive control (FCS-MPC) strategy. Compared to the two-level inverter, the drifted neutral point potential is an issue that cannot be neglected. To resolve this issue, the cost function is modified in this paper. Besides, as all of the voltage vectors are employed during optimal research progress in FCS-MPC, the switching frequency is variable, which burdens the filter. The complex calculation progress also burdens the microcontroller. According to the conventional modulation algorithm, the voltage vectors are divided into several groups and the optimal calculations are simplified with them. Based on that modification, the switching frequency is fixed. Finally, the simulation and the experimental results are demonstrated, which reveal the validity and merits of the proposed method.
The transport of pathogenic bacteria from wastewater treatment facilities in subsurface has attracted extensive concerns over recent decades, while the impact of effluent water chemistry remains unclear. The influence of retention time in effluent from a municipal wastewater treatment plant on bacterial surface properties and deposition of Escherichia coli strains in saturated quartz sand packed-bed columns was investigated in this paper. Retentions in effluent significantly altered bacterial surface properties, such as zeta potential, surface charge and hydrophobicity, subsequently changed their deposition rate coefficients and attachment efficiencies in quartz sand packed-bed columns. Under low ionic strength conditions, bacterial deposition onto quartz sand grains was in agreement with the predictions of DLVO theory, in which the secondary energy minimum was demonstrated to be predominant.
A novel topology of isolated input-series and output-series (ISOS) full-bridge bidirectional DC/DC converter is described in this paper for the application requirement of high input voltage and high output voltage, which can be used in the next generation medium and high voltage power conversion systems. The proposed novel isolated bidirectional DC/DC converter not only can apparently decrease the stress of the switches, but also have the advantages, such as galvanic isolation, ease of realizing soft-switching control, high power density, and so on. In this paper, working principle of the proposed DC/DC converter is discussed in detail, the corresponding equations are derived, and the soft switching implementation is discussed too. In the end, simulation is done through PSIM to certify the feasibility of the proposed DC/DC converter and accuracy of the criterion.
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