No abstract

As a class of nonlinear loads in the power system, electric vehicle chargers will produce a certain harmonic pollution for the grid. Before the construction of charging stations, it is necessary for electric vehicle charger (station) connected to the grid to simulate and predict harmonics. The models of single charger and charge station are built separately in order to simulate and analysis the impact of a single and multiple chargers on power quality. The factors of the harmonic current ratio (HRI) and the current total harmonic distortion (THDI) varied with the charging power and the number of the chargers are discussed and analyzed. The generation mechanism of harmonic counteraction and interaction between the chargers are analyzed. The simulation results show that: because of the impedance of the system and the transformer, the harmonic current ratio (HRI) and the current total harmonic distortion (THDI) both increase firstly to some extent and subsequently decrease gently with the increase of the number of the chargers in the same power charging. This phenomenon has nothing to do with the harmonic counteraction and how that happen is discussed and analysis in this paper. And the phenomenon of harmonics interaction and counteraction occurs with the increase of the number of the chargers in different power charging, and the current total harmonic distortion (THDI) declines and tends to maintain a relatively stable value.

The major rock types of Ordovician Majiagou Formation Ma541 Submember in western Jingbian Tableland include muddy dolomite, gypsum-bearing dolomite, gypsum dolomite, limy dolomite, and muddy powder crystal dolomite. This paper is based on the theory of sedimentary petrology and with the methodology of comprehensive mapping by using single factors to analyze multiple factors.Using stratum thickness, the content of gypsum and penecontemporaneous dolomite as single factors, we studied the lithofacies palaeogeography in Ma541 Submember.The results show that Ma541 is generally a set of sedimentation from supratidal limited evaporation environment and in the period of sea level decline with shallow water. The sedimentary microfacies are mainly composed of gypsum-bearing dolomitic flat and gypsum dolomitic flat ,dolomitic gypsum flat comes second. We combined the areas regional geological background with lithofacies palaeogeography to construct the limited evaporation tidal flat sedimentation maps of Ma541 Submember. Meanwhile,the control of reservoirs was studied. We thought that gypsum-bearing dolomitic flats and dolomitic flats provide a foundation for the development of large-area reservoirs.

The terrace deposits in a river valley are key records to the research of fluvial sequence stratigraphy. Terrace deposits and the basal sequence boundary comprise the half-cycle of base level fall, and the fluvial infillings belong to the half-cycle of base level rise. Thus, terrace deposits and the basal sequence boundary are part of the regressive systems tract, and should be separated from the transgressive or lowstand systems tracts in previously published littoral fluvial sequence stratigraphic models. In addition, in the upstream portions of the fluvial system where sea level cannot reach, the fluvial sequence is influenced by tectonism and/or climate. The terrace deposits can provide specific information about the main controlling factor (e.g., tectonism or climate) and its varying pattern during the half-cycle of base level fall. Because the two half-cycles of base level fall and rise are at the same stratigraphic levels and belong to the same base level cycle, it is possible to research the controlling factor and its varying pattern during the rising half-cycle, which will be significant to an inland fluvial sequence stratigraphic model. Finally, the authors assert that seeking isochronous parasequence correlation based on 4-division models (4 different systems tracts), along with the blend of sedimentology and geomorphology and diversification of models based on different controlling factors will collectively produce more robust-interpretations of fluvial sequence stratigraphy in the future.