Investigation on Common-Mode Voltage Suppression in Smart Transformer-Fed Distributed Hybrid Grids

Rongwu Zhu, Giampaolo Buticchi, Marco Liserre

Research output: Journal PublicationArticlepeer-review

27 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)8438-8448
Number of pages11
JournalIEEE Transactions on Power Electronics
Issue number10
Publication statusPublished - Oct 2018


  • Common-mode (CM) voltage
  • smart transformer (ST)
  • three-phase four-leg converter
  • three-phase four-wire system
  • unbalanced three-phase loads

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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