Effects of Control Strategy and Calibration on Hybridization Level and Fuel Economy in Fuel Cell Hybrid Electric Vehicle

Using dynamic causal models for a direct-hydrogen fuel cell and a DC/DC converter we design decentralized and multivariable controllers regulating the bus voltage and preventing fuel cell oxygen starvation. Various controller gains are used to span the fuel cell operation from load-following to load-leveling, and hence, determine the required fuel cell-battery sizing (hybridization level) and the associated trends in the fuel economy.

Our results provide insight on the strategy and calibration of a fuel cell hybrid electric vehicle with no need for a supervisory controller that typically depends on optimal power split during a specific driving cycle. The proposed controllers directly manipulate actuator commands, such as the DC/DC converter duty cycle, and achieve a desired power split. The controllers are demonstrated through simulation of a compact sedan using a mild and an aggressive driving cycle.