Design and control of air supply system for PEMFC UAV based on dynamic decoupling strategy

Abstract

The oxygen excess ratio (OER) and air pressure of the proton exchange membrane fuel cell (PEMFC) cathode need to be relatively stable to improve energy conversion and utilization. However, the OER and air pressure adjustments are coupled in the centrifugal compression system and the fluctuations of OER and pressure may cause oxygen starvation and destroy the pressure balance between anode and cathode respectively, affecting the output power and service life of PEMFC. When the PEMFC unmanned aerial vehicle (UAV) performs the mission, the nonlinearity and time-varying characteristics of the model bring greater challenges to the design and control of air supply system for PEMFC UAV. Firstly, in view of nonlinear factors such as the variable space environments and different load conditions, an air supply system model suitable for PEMFC UAV is established. Secondly, in order to supply stable voltage to the UAV load and the air compressor through the DC/DC power converter as well as reduce PEMFC output power loss and device stress, a four-phase interleaved boost converter (IBC) and controller are designed. The devised IBC and its control scheme are beneficial to decrease energy loss and strengthen the anti-interference ability for high-power PEMFC applications. What’s more, based on the air compressor dynamic model as well as the analysis of the static and dynamic characteristics of PEMFC system, the power consumption relationships among the external UAV load, the internal compressor load, and the stack source are analyzed in detail. Then, when considering the strong coupling and nonlinearity of the mass flow and the pressure under the variable-altitude centrifugal compression system, we propose a dynamic decoupling strategy for OER and pressure control based on fuzzy logic. Finally, compared with the results of PI controllers and feedforward compensation decoupling controllers, the fuzzy decoupling controllers can realize the rapid adjustment of OER and maintain the stability of air pressure robustly.