PROJECT TITLE :

Beat Frequency Oscillation Analysis for Power Electronic Converters in DC Nanogrid Based on Crossed Frequency Output Impedance Matrix Model - 2017

ABSTRACT:

The interaction of power electronic converters in a microgrid will introduce system instability and power quality problems. Existing investigations specialize in interactions either in low-frequency regions, such as the constant power load, or in very high-frequency regions like electromagnetic interference. However, interactions of power converters around their switching frequency range are not included. In truth, the interaction of dc-dc converters with different switching frequencies can introduce beat frequency oscillation in bound cases. Since further frequency element (beat frequency) is generated, ancient impedance concept is not the tool for beat frequency oscillation analysis and new models want to be developed. During this paper, a crossed frequency output impedance matrix model is proposed to describe the terminal characteristics of a dc-dc converter around its switching frequency range. A high-frequency equivalent circuit model for the converter is then developed to predict the beat frequency oscillation in parallel and cascaded systems, which results from the interaction of power converters with different switching frequencies. Finally, design tips are proposed to avoid potential beat frequency oscillation during a dc nanogrid. Experimental results for both parallel and cascaded systems validate the accuracy and effectiveness of the proposed prediction method and design pointers.