Circulating-Current Indices for Three-Phase Boost Rectifiers with Different Ratings

In this paper, a general definition of circulating currents for each phase of each paralleled converter with different rating is first proposed. Then, based on this definition, the corresponding circulating current index, gammakj , and unbalance rate, beta _j , for paralleled converter j are proposed to provide one with a quantitative measure about the serious status of the circulating current just like the commonly used total harmonic distortion (THD) factor. Third, the corresponding general model of circulating currents is also derived for understanding the governing dynamic behavior of circulating currents. Finally, some examples are also given to illustrate the significance of the proposed indices and as a verification of the validity of the derived general model.