Maximum Power Extraction From Series-Connected Fuel Cell Stacks by the Current Compensation Technique

Abstract

Fuel Cell stacks, due to their low voltage output, are usually connected in series to achieve higher voltages in typical high-power applications. Power from individual stacks varies dynamically during their operation because of variation in operating parameters such as temperature, humidity, flow rates, ageing, etc., which results in mismatch of electrical performance of the stacks. When one of the series-connected stacks is under performing, the current from the branch is affected leading to reduced power. This paper proposes a novel scheme, to extract maximum power from series-connected stacks by current compensation which also improves reactants economy. A minimal power-processing (compensating) power converter is used with each stack to achieve maximum power extraction. Since activation of compensation is not effective during low-power operation, an algorithm is developed to implement compensation only for the performance improvement zone. Compensating converters are designed using interleaved fly-back topology, for reduced ripple, with DSP TMS320F2812.The efficacy of the technique is analyzed using Simulink. Experimental results are presented to validate the proposed scheme.