Stack and converter-integrated design for efficient residential fuel cell system

The stack of a residential fuel cell power generation system has low voltage and high current output characteristics. Due to which it is difficult for the converter to achieve high efficiency. Therefore, efficiency improvement is an important issue in the converter design. And in the current references about the efficient converter design, the stack parameters are supposed to be fixed before the converter design begins. This paper first investigates the relationship between the stack parameters and the converter efficiency. Based on the theoretical derivations, a novel stack and converter integrated design scheme is proposed to improve and optimize the converter efficiency. Full bridge is widely used as the DC-DC converter topology for medium and large power range, which is also used as an example in this paper. The full bridge converter can be classified between voltage fed and current fed types depending on their input circuit. This paper first analyses and compares the efficiency of the two converter types at fixed power, when the stack operating voltage is sweeping from low to high. The results show that the efficiency trends of the two converter types are monotone and in opposite directions with one intersection. A detailed description of the stack design later in this paper proves that even with the fixed stack power, the stack parameters design can change the stack operating voltage. Therefore, the stack parameters design determines the converter efficiency and which converter is more efficient. When the more efficient converter is chosen, the stack parameters design can be further optimized to improve the specific chosen converter efficiency by changing the stack operating voltage. Finally, it is concluded that the stack and the converter integrated design contributes to the fuel cell system efficiency improvement.