Methodology of designing durability test protocol for vehicular fuel cell system operated in soft run mode based on statistic results of on-road data

In a polymer electrolyte membrane (PEM) fuel cell bus, there are at least two power sources, e.g., a hydrogen fuel cell system (FCS) and an energy storage system (ESS). Depending on powertrain configuration and control strategies, an FCS can work in different modes, which can be generally classified into so-called power follow (PF) and soft run (SR) modes. In the SR mode, the FCS serves as a stationary power source, and the ESS provides the dynamic power. Nowadays, most of the fuel cell buses in China operate in this mode, since it has advantages of long working lifetime. In order to evaluate the aging behavior of fuel cell stacks under conditions encountered in this kind of fuel cell buses, new durability test protocols based on statistical results obtained during actual driving tests are required. In this research, we propose a methodology for designing fuel cell durability test protocols that correspond to the SR mode. The powertrain configuration and control strategy are described herein, followed by a presentation of the statistical data for the real driving cycle in a demonstration project. Equations are derived based on constraints of keeping the battery in charging balance. One test protocol is presented as an example, and compared to existing protocols with respect to common factors, such as time at open circuit voltage and root-mean-square power.