This paper extends the use of the versatile buck-boost converter to power manage a parallel hybrid system topology as an alternative to the well-known serial hybrid (SH) topology and the most recent series-parallel hybrid (SPH) topology. These systems utilize a proton exchange membrane fuel cell as the primary source in combination with an auxiliary storage device (ASD), and the selected converter is in charge of the power management between the sources (fuel cell or ASD) and the load. Therefore, the converter has a very important role in the system since it is responsible of ensuring a dc-bus voltage regulation with a safe and reliable operation of the entire system while also guarantee a high power conversion efficiency. Hence, this is the third topology, where the coupled-inductor dc-dc buck-boost converter is studied to demonstrate and exploit its advantages such as noninverting voltage step-up and step-down, high efficiency, regulation of input and output currents and low ripple values, and the ability to change from input to output current regulation loop, suddenly and smoothly, and vice versa. In order to determine which topology (SH, PH, or SPH) exhibits the highest power conversion efficiency under a certain load profile, it is important to ensure a fair efficiency comparison that will only reflect the properties of the topology and not its individual components. Therefore, the same design criteria, the same control, and the same components were used for all the studied topologies. Simulation and experimental results have been validated on a 48-V 1200-W dc bus.

In this paper, a serial-parallel hybrid (SPH) power system formed by a fuel cell (FC), an auxiliary storage device (ASD), and the current-controlled dc-dc converters responsible for the power management are realized by using the digital signal controller (DSC) TMS32F28335. The main energy management goal is to transfer energy from the sources (FC or ASD) to the load while ensuring dc bus voltage regulation and high power conversion efficiency. In addition, a safe and reliable operation of the system has to be achieved. The selected converter and its controller features are noninverting voltage step up and step down, high efficiency, regulation of input and output currents and low ripple values, and the ability to change from input to output current regulation loop, suddenly and smoothly, and vice versa. All these features allow it to be positioned in different FC system localizations and simplify the design of the master control. Simulation and experimental results have been validated on a 48-V 1200-W dc bus.

This paper presents the design guidelines of a series hybrid fuel cell system, including control and protection loops. This hybrid system consists of a fuel cell (FC), an auxiliary storage device (ASD), and current-controlled DC-DC converters responsible for managing the energy transfer between the FC, the ASD, and the load. The main advantages of the selected converter are its voltage step-up and step-down properties, high efficiency, and low input and output current ripples, which enable it to be positioned in all system locations, provided the corresponding controllers are suitably designed. Also, using the same module for all system converters simplifies the design and construction tasks. The theoretical analyses have been verified by simulations and validated experimentally on a 48 V 1500 W purpose-built DC bus.

Robust control techniques for power converters are becoming more attractive because they can meet with most demanding control goals like uncertainties. In this sense, the Takagi-Sugeno (T-S) fuzzy controller based on linear matrix inequalities (LMI) is a linear control by intervals that has been relatively unexplored for the output-voltage regulation problem in switching converters. Through this technique it is possible to minimize the disturbance rejection level, satisfying constraints over the decay rate of state variables as well as the control effort. Therefore, it is possible to guarantee, a priori, the stability of the large-signal converters in a broad operation domain. This work presents the design of a fuzzy control synthesis based on a T-S fuzzy model for non-minimum phase dc-dc converters, such as boost and buck-boost. First, starting from the canonical bilinear converters expression, a Takagi-Sugeno (T-S) fuzzy model is obtained, allowing to define the fuzzy controller structure through the parallel distributed compensation technique (PDC). Finally, the fuzzy controller design based on LMIs is solved for the defined specification in close loop through MATLAB toolbox LMI. Simulations and experimental results of a 60 W prototype are presented to verify theoretical predictions.

The digital current control method of switching converters studied in this work is based on taking more than one sample per switching period of the instantaneous current error waveform. To correctly regulate the average current value, as well as to simplify the system model, the controller must include a ripple filter. The proposed system includes a new low-phase-lag ripple filter. The whole system is first modelled in the s-domain to easily include the plant dynamics. The validity of the s-domain analysis up to half the switching frequency, once the controller is converted into the z-domain, has been verified by simulating its frequency response and its transient behavior. In comparison with other digital control methods, our approach provides a good general performance with a reasonable level of complexity.