This paper will revise, experimentally investigate, and discuss the main application challenges related to gallium nitride power semiconductors in switch-mode power converters. Gallium Nitride (GaN) devices are inherently gaining space in the market. Due to its high switching speed and operational switching frequency, challenges related to the circuit design procedure, passive component selection, thermal management, and experimental testing are currently faced by power electronics engineers. Therefore, the focus of this paper is on low-voltage (<650 V) devices that are used to assemble DC-DC and/or DC-AC converters to, for instance, interconnect PV generation systems in the DC and/or AC grids. The current subjects will be discussed herein: GaN device structure, the advantages and disadvantages of each lateral gallium nitride technology available, design challenges related to electrical layout and thermal management, overvoltages and its implications in the driver signal, and finally, a comprehensive comparison between GaN and Si technology considering the main parameters to increase the converters efficiency.

Low Voltage DC microgrids emerge as a viable alternative to AC microgrids. A large research interest is noted towards fast and selective protection of DC grids, typically focusing on hybrid or full solid state solutions. In this paper, the use of fuses as short-circuit protection in Low Voltage DC microgrids is evaluated. The main advantage of fuses is that they are simple, cheap, standardized and have low steady state losses. A theoretical basis is formed to model DC short-circuit currents in grids with a limited short-circuit availability. The outcomes are applied to evaluate the possibilities of fuse protection in LVDC grids. It was found that fuses are an effective means of protection, although the required amount of capacitance at the output of the voltage balancing converter can be high, which impacts the total system cost. A fuse based protection strategy is presented that highlights the need for additional capacitance to clear faults compared to the necessary capacitance for system stability. An experimental setup was built to validate the claims.

Since building-integrated photovoltaic (BIPV) modules are typically installed during, not after, the construction phase, BIPVs have a profound impact compared to conventional building-applied photovoltaics on the electrical installation and construction planning of a building. As the cost of BIPV modules decreases over time, the impact of electrical system architecture and converters will become more prevalent in the overall cost of the system. This manuscript provides an overview of potential BIPV electrical architectures. System-level criteria for BIPV installations are established, thus providing a reference framework to compare electrical architectures. To achieve modularity and to minimize engineering costs, module-level DC/DC converters preinstalled in the BIPV module turned out to be the best solution. The second part of this paper establishes converter-level requirements, derived and related to the BIPV system. These include measures to increase the converter fault tolerance for extended availability and to ensure essential safety features.

This paper evaluates the power conversion efficiency of the buck three-level DC-DC converter, when operating in unbalanced bipolar DC microgrids. Bipolar DC microgrids adopt a positive, neutral and negative wire to double the power transfer capability, reduce conduction losses and provide two voltage levels. Additional converters are however required to balance the pole-to-neutral voltages in the presence of unbalanced loading conditions. Previous work has shown that the buck three-level DC-DC converter features voltage balancing capability and can serve, at the same time, as an interface for battery storage and photovoltaic systems for example. Nevertheless, available conversion loss models are only valid for balanced loading conditions. Therefore, this paper derives a conversion loss model for a buck three-level DC-DC converter, also valid in unbalanced conditions. The model is decomposed in balanced and unbalanced components in order to separate losses arising in balanced and unbalanced conditions. Furthermore, the model accounts for non-ideal common-mode currents as experimental results will reveal that they have a profound impact on the conversion efficiency in unbalanced and balanced conditions.

In this paper, a family of interleaved high-step-down (I-HSD) DC-DC converters is proposed integrating the Valley-Fill switched capacitor structure and a double series capacitor Buck converter. This integration generates three converters, which will be extensively explored herein via theoretical, simulation and experimental analysis. A complete theoretical analysis of the structures is presented in order to mathematically explain the physical operation of the proposed topologies. A design procedure is presented for the following specifications: 300 V/12 V input to output voltage, 100 W of power and a switching frequency of 100 kHz and the results obtained are compared to state-of-the-art DC-DC converters that enable similar high step-down operation.