Loop-shaping control of high-step converters for fuel-cell applications

Fuel-cell stacks are an attractive option for power generation; however, this technology presents some drawbacks as slow dynamic response and low unregulated DC output voltage, which depends nonlinearly on the output current. In this paper, a quadratic boost converter with a single active switch is proposed as an interface between a PEM fuel-cell stack and a load. The proposed topology is used to increase the output load voltage for a given stack-converter-load system, aiming to ensure high conversion ratios. In addition, a loop-shaping average current-mode scheme using a single control signal is proposed for load-side voltage regulation. A selection procedure for controller parameters ensuring system stability and output voltage regulation is established. Experimental results are shown in a 220 V @ 400 W prototype. Finally, system stability is verified via experimental frequency response and controller performance is tested by applying step changes in the load.