000K utf8 1100 $c2017 1500 eng 2050 urn:nbn:de:gbv:8-publ-16412 2051 10.1109/TPEL.2017.2779803 3000 Zhu, Rongwu 3010 Buticchi, Giampaolo 3010 Liserre, Marco 4000 Investigation on Common Mode Voltage Suppression in Smart Transformer-fed Distributed Hybrid Grids [Zhu, Rongwu] 4209 High-frequency (HF) switching and ac-side unbalanced loads challenge smart transformer (ST)-fed hybrid grids (both ac and dc), causing common-mode (CM) voltage variations and dc-link oscillation. The HF switching introduces an HF CM voltage and the ac grid unbalanced loads introduce a fundamental frequency CM voltage in hybrid grids. The CM voltage in ST-fed distributed grids degrades the power quality, threatens the safety of the connected devices, and potentially constitutes a health risk for the operators of such devices. Therefore, this paper systematically analyzes the root causes of the ST CM voltage variations and the impacts on hybrid grids. Based on the two typical configurations (three- and four-leg converters), the performance and requirements of CM inductor filter and bypass CM filter on HF CM voltage suppression are studied in detail. By considering the CM voltage suppression and dc capacitor lifetime, a four-leg converter with improved modulation strategy and small dc bypass film capacitor is proposed. The simulation and experimental results clearly verify the feasibility and correctness of the proposed strategies. 4950 https://doi.org/10.1109/TPEL.2017.2779803$xR$3Volltext$534 4950 https://nbn-resolving.org/urn:nbn:de:gbv:8-publ-16412$xR$3Volltext$534 4961 https://macau.uni-kiel.de/receive/publ_mods_00001641 5051 621.3 5550 Common mode voltage 5550 smart transformer 5550 three-phase four-leg converter 5550 three-phase four-wire system 5550 unbalanced three-phase loads