Experimental study of the dynamic and transient characteristics of sub-health fuel cell multi-stack systems without DC/DC

Abstract Multi-stack fuel cell systems without DC/DC converters can greatly reduce cost, efficiency loss, and particularly appropriate for weight-constrained applications. In this study, two sub-health fuel cell stacks with poor consistency were applied to study the dynamic and transient characteristics, power adaptive allocation and output stability in no-DC/DC series and parallel architectures. The results show voltage difference, voltage overshoot rate and undershoot rate in the series system are positively correlated with current loads, and the poor performance stack is more serious. In the parallel structure, the output currents are unequal and the current difference goes up with the increase of loads. Furthermore, extremely current overshoot and backflow phenomenon were observed at the moment of one fuel cell suddenly turned on. Unexpectedly, the transient backflow current flows through the same point when it rebounds and the poor consistency fuel cell stacks have similar transient current. The terrific result is the fuel cells run steadily and less than 50 ms transient process in both structures. The results not only indicate the proposed architectures are feasible and provide a foundation research for no-DC/DC multi-stack systems management, but also lay a novel reference for the improvement and verification of the fuel cell transient mathematical model.