No abstract

This paper presents a space vector modulation strategy for a three-phase indirect matrix converter to reduce the common-mode voltage and maintain the output performance. To reduce the peak value of the common-mode voltage to 57.7% of the input phase voltage, three active voltage vectors are used to generate the desired output voltage with arbitrary amplitude and frequency, instead of using both active and zero voltage vectors as in the traditional space vector modulation strategy. Although the common-mode voltage is reduced, the output waveform quality of the three-phase indirect matrix converter deteriorates due to the absence of the zero voltage vectors. To overcome this problem, the proposed space vector modulation strategy is redesigned to control the rectifier stage of the indirect matrix converter by utilizing three active current vectors instead of two as usual. Consequently, the constant average dc-link voltage is achieved, which can improve the output performance in terms of the output voltage and current harmonic distortion. The simulation is implemented by PSIM software and experimental results are provided to verify the effectiveness of the proposed space vector modulation strategy.

This work continues a series of publications on the diversity of the main groups of invertebrates found through the investigation of meiobenthic communities in various inland waterbodies in central and southern Vietnam. Here, a checklist of oligochaetes and aeolosomatids (the annelid worms) discovered for the period 2010–2021 is presented, as well as data on the structure and abundance of their populations found in the country, ecology, local and global distribution, and, where necessary, taxonomic, morphological and other comments. In total, 71 representatives of the species and supra–species ranks from 3 families and 17 genera are listed. In total, 39 representatives were identified to the species level. During the present research, 2 species new to science were discovered and described in previously published works. This paper reports 9 more forms that need further study and may belong to still undescribed species. In addition to the new and still-unidentified species, the checklist reports about 30 more members of species and supra–species ranks that were recorded in Vietnam for the first time. Based on new and previously published data, the currently known diversity of aquatic oligochaetes and aeolosomatids in Vietnam is estimated at approximately 100–113 and 8–9 representatives, respectively. It is shown that members of the family Enchytraeidae remain practically unexplored in the waterbodies of the region. The subfamily Tubificinae and the family Aeolosomatidae also continue to be relatively poorly studied here at the species level.