Modeling and control of circulating currents for parallel three-phase boost rectifiers with different load sharing

In this paper, a general definition of circulating currents for each phase of each paralleled converter with different load sharing is first proposed. Then, based on this definition, the corresponding circulating current index gamma(kj) and unbalance rate beta(j) for paralleled converter j are proposed to provide one with a quantitative measure about the serious status of power quality. Third, the corresponding general model of circulating currents is also derived for understanding the governing dynamic behavior of circulating currents. Fourth, based on the derived model, the proposed coordinate control strategy is then proposed for different load sharing controls, as well as elimination of circulating currents. Furthermore, a prototype system is also constructed, and the proposed coordinate control is implemented using TMS320F2812 digital signal processor. Both simulation and experimental results indeed show the effectiveness of the proposed coordinate control.