Abstract

Modeling the unintended common- and differential-mode (CM and DM) behavior of multi-converter power electronic-based systems can be a challenge. Chief among the issues is the need for detailed knowledge of the converter hardware to determine model parameters. In this paper, a focus is on the derivation of Thevenin-based models that only require characterization at the converter terminals. Periodic linear time varying system analysis is first used to derive and consider the applicability such models. Subsequently, methods to experimentally characterize Thevenin parameters are established. The modeling approach is then used to establish worst-case predictions of CM/DM behavior of a microgrid which is validated using both time-domain simulation and hardware experiment.

Highlights

  • It is increasingly common that micro-grids are composed of multiple tightly-coupled power electronic (PE) converters

  • The high-frequency on/off modulation of transistors/switches is known to cause unintended common-mode (CM) voltage/current that can lead to insulation failure, bearing failure in electric machinery, and electromagnetic interference (EMI) [2]–[5]

  • The periodically linear time-varying (PLTV) analysis is first considered for the case of a buck converter operating in continuous conduction, in which a slight difference in the input filter inductance on the positive/negative rails creates an imbalance that leads to CM/DM coupling

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Summary

INTRODUCTION

It is increasingly common that micro-grids are composed of multiple tightly-coupled power electronic (PE) converters. The PLTV analysis is first considered for the case of a buck converter operating in continuous conduction, in which a slight difference in the input filter inductance on the positive/negative rails creates an imbalance that leads to CM/DM coupling It is considered for a diode rectifier circuit, where commutation leads to time-varying conduction paths that result in the CM/DM coupling. It is shown for the buck converter that an accurate LTI model can be established. The CM/DM modeling approach set forth in this research provides a path forward in that the frequency-domain behavior of converters (characterized independently) can be used to predict a worst-case system-level behavior This opens the potential to establish system-level standards akin to those used for individual converters. Motivation to utilize the LTI form is model and characterization simplicity, which is highlighted in the subsequent section

PLTV Analysis
PLTV TCDMEC
TCDMEC for Buck Converter
Remarks
THE VENIN CHARACTERIZATION PROCEDURE
SYSTEM-LEVEL DEMONSTRATION
Simulation Study
Hardware Study
CONCLUSION

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