Delay-Based Voltage-Mode Control of Switched DC-DC Buck Converters for Fuel-Cell Power Applications

In this paper, the use of intentional delays to control the power stage of a fuel-cell system is discussed. A Proportional-Retarded (PR) controller, is designed to accelerate the dynamic response of a switched DC-DC buck converter with the objective of quickly compensating for parametric variations without creating undesired oscillations in the duty cycle. A numerical evaluation of the feedback control loop shows that the PR controller is a preferable substitute to benchmark Proportional-Derivative (PD) control implementations for fuel-cell applications and demonstrates that delays can have positive effects in switched systems, in contrast to what is commonly assumed in the open literature. The proposed PR controller is further complemented with an integral term to obtain the Proportional-Integral-Retarded (PIR) controller able to cope with input voltage variations and sudden load changes. Simulation results verify the advantages of the proposed approach.