Circulating Currents Suppression Based on Common Mode and Differential Mode Control in DC Distribution Systems

In dc distribution systems., to increase the system power capacity., making several H-bridge dc/dc converters connected in parallel is a feasible method. Although this method can usually achieves the intended purpose., there are some headaches. Among them, the circulating current is the one that has the greatest impact on the safety and efficiency of the system. Therefore, the circulating currents among converters must be suppressed to a small enough value for system stability. To address this issue., this paper proposes a new control strategy from the perspective of the system. Concretely., to find the essential cause of the circulating currents, this paper analyzes the circuit structure of the system in detail and establishes the specific model of the circulating currents. Through this model., we find that the circulating currents in the system are very complicated., including two types. The one is in the single H-bridge dc/dc converter., and the other one is among the several parallel converters. Then to deal with these two kinds of circulating currents., the proposed method includes two control components. Specifically., the circulating current in the single converter is suppressed by the common mode component., and those among the several parallel converters are suppressed by the differential mode component. The real-time hardware-in-loop (HIL) tests are carried out to verify the theoretical analyses.