Analysis of EMI Issues in DC-Microgrids Due to Power Electronic Converters

Krishna, Angaline Reshmi
Gunawardane, Kosala
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Master of Engineering
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Auckland University of Technology

This research provides an overview of a MATLAB/Simulink model of the DC Microgrid system and presents key results from simulation studies undertaken to estimate the conducted electromagnetic interference arising from the interactions between power converters. This research has investigated how multi-converters in a DC Microgrid system, contribute to the generation of aggregated conducted electromagnetic interference. An islanded DC Microgrid model was built and simulated with and without the presence of the EMI suppressing filters. Spectrum analysis was performed on the DC-DC converters using several DC Microgrid topologies to analyse the EMI emissions in the DC Microgrids due to the interactions between its multiple power converters of different switching frequencies. The simulation results obtained, supported by the mathematical analysis, confirmed that in multi-converter systems, aggregated conducted electromagnetic interference is more prevalent in DC Microgrid topologies where the power converters have different switching frequencies relative to the DC Microgrid models where converters have similar switching frequencies. It was also found that custom-tuned PID-controlled DC-DC converters helped reduce the aggregated conducted electromagnetic interference in contrast to the un-tuned PI/PID controlled converters. It was also noted that the PID-controlled converters were more effective in minimizing the electromagnetic interference than the PI-controlled converters, due to their enhanced stability. Overall, the research findings indicated that the DC Microgrid models having tuned PID controlled power converters of similar switching frequencies, generated reduced aggregated conducted electromagnetic interference relative to models having converters of different switching frequencies. It was also ascertained that having a pair of the common-mode and differential-mode EMI suppressing filters in the DC MG models, was more effective in reducing the EMI generation compared to models having four pairs of the EMI suppressing filters, i.e., having one pair of filters per each PID controlled power converter.

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