iTCM-Operated Three-Phase Three-Wire Voltage-Source Converter System Featuring Capacitor-Split Virtual Ground Connection

Gang Zhang, Yang Wu, Junzhong Xu, Thiago Batista Soeiro

Research output: Contribution to journalArticleScientificpeer-review

Abstract

High efficiency can be achieved in grid-connected converters (GCC) by implementing a zero voltage switching (ZVS) mechanism, such as the integrated triangular current mode (iTCM) modulation, which reduces the switching losses in the semiconductors. The iTCM can be readily adapted to a three-phase three-wire voltage source converter (VSC) with the help of virtual ground (VG), which decouples the operation of three-phase switching cells. However, conventional methods of VG have all the zero-sequence currents flowing through the DClink capacitors, resulting in an increase in the RMS current, hence extra loss for those passive components. This paper, thus, introduces a capacitor-split VG topology that can relieve this issue by excluding the DC-link capacitors from the circulating path of the main zero-sequence currents, helping to reduce current stress for the DC-link capacitors. This topology is characterized by its filter capacitors being split into two halves and connected to the top and the bottom DC rails, respectively. Herein, the working principles of the proposed iTCM-operated three-phase three-wire VSC are comprehensively explained, and a detailed design guideline for the LC branch and LCL filter is offered. Analytical models for component stresses and the reverse current waveform have been developed and corroborated through PLECS simulations. A 3-kW, heatsink-less VSC system was constructed and tested, confirming both the system's effective functionality and the enhanced power efficiency of the proposed capacitorsplit VG connection. Therein, the studied system demonstrated a significant efficiency improvement, ranging from 0.51% to 2% across the entire operating power spectrum, as compared to the conventional VG connection in iTCM-operated VSCs.

Original languageEnglish
Pages (from-to)1-15
Number of pages15
JournalIEEE Transactions on Power Electronics
DOIs
Publication statusE-pub ahead of print - 2024

Keywords

  • Bidirectional Rectifier
  • Integrated Triangular Current Mode
  • Power Factor Correction
  • Voltage Source Converter
  • Zero Voltage Switching

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