Unmanned Aerial Vehicles were first introduced almost 40 years ago and their applications have increased and diversified substantially since then, in both commercial and private use. One of the UAVs main issues when it comes to mobility is that the power sources available are inadequate, this highlights an area for improvement as the interest in drones is on the increase. There exist many different types of power supplies applied to UAVs, however each has their own limitations and strengths that pertain to weight contributions, charging and discharging times, size, payload capabilities, energy density and power density. The aim of this paper is to review the main power sources available for UAVs, determine their shortfalls, compare the power sources with each other and offer suggestions as to how they can be improved – hence identifying where the gap lies for developing better alternative power sources.

Bipolar dc grid systems are fast gaining attraction for renewable energy source integration, because of their merits of higher reliability, efficiency, and robustness as compared to the unipolar dc grids. However, the progress in multiport converters, resulting into lower cost and more compact design for bipolar microgrid systems, is fairly slow. Therefore, this article proposes a novel family of five nonisolated multiport dc–dc converter topologies with bipolar symmetric outputs. The performance and key operational features of the proposed converters under varying input voltages, duty cycles and loads are numerically verified and experimentally on an in-house test setup to prove the concept of the proposed converters. In the experimental validation, the operation of the converter under simultaneous and arbitrary individual power transfer from two input ports is tested. Furthermore, the easy integration of the proposed converters with a multilevel inverter to achieve high-quality ac voltages is demonstrated. As compared to the few existing counterparts, the proposed converters have a competitive edge in terms of higher number of input ports and voltage gains. Alongside the possibility of arbitrary independent power flow from the input ports, inherently symmetrical outputs require a simple balance control for asymmetrical members of the family.

There has been increasing interests in the use of double layer capacitors (DLCs)—most commonly referred to as supercapacitors (SCs), ultra-capacitors (UCs), or hybrid capacitors (HCs)—in the field of power electronics. This increased interest in the hybridization of energy storages for automotive applications over the past few years is because of their advantage of high power density over traditional battery technologies. To facilitate accurate design and simulation of these systems, there is a need to make use of accurate and well validated models. Several models have been postulated in literature, however, these models have various limitations and strengths, ranging from the ease of use down to the complexity of characterization and parameter identification. The aim of this paper is to review and compare these models, specifically focusing on the models that predict the electrical characteristics of DLCs. The uniqueness of this review is that it focusses on the electrical circuit models of DLCs, highlighting the strengths and weaknesses of the different available models and the various areas for improvement.

This paper proposes a novel three-phase transformer-based multilevel inverter (MLI) topology to maximize the output voltage levels for high-power high-voltage applications while reducing component counts as compared to its transformer-based counterparts. The proposed hybrid topology is formed by connecting a three-level T-type module with full H-bridge cells through single-phase transformers. The T-type module is fixed while the full H-bridge cell can be repeated for enlarging the output voltage levels without increasing the voltage stress on switches. Key features of the proposed topology include low part count, capacitor-free, diode-free, voltage boosting, simple control, and modularity. Within the framework, a simple low-frequency pulse width modulation (LFPWM) switching scheme is used to control the output voltage, and the working principle is detailed for seven-, nine-, and N-level operation. The operability and performance of the proposed topology are numerically verified and experimentally validated at different loads. Moreover, its conversion efficiency is experimentally examined. Finally, a comparative study with existing transformer-based MLI circuits is conducted to prove its key merits.

As the need for green and effective utilization of energy continues to grow, the advancements in the energy and power electronics industry are constantly driven by this need, as both industries are intertwined for obvious reasons. The developments in the power electronics industry has over the years hinged on the progress of the semiconductor device industry. The semiconductor device industry could be said to be on the edge of a turn into a new era, a paradigm shift from the conventional silicon devices to the wide band gap semiconductor technologies. While a lot of work is being done in research and manufacturing sectors, it is important to look back at the past, evaluate the current progress and look at the prospects of the future of this industry. This paper is unique at this time because it seeks to give a good summary of the past, the state-of-the-art, and highlight the opportunities for future improvements. A more or less ‘forgotten’ power electronic switch, the four-quadrant switch, is highlighted as an opportunity waiting to be exploited as this switch presents a potential for achieving an ideal switch. Figures of merit for comparing semiconductor materials and devices are also presented in this review.

This research introduces an innovative converter system which has been developed to seamlessly incorporate multiple sources of renewable energy into both DC and AC grids. The integration of multiple energy sources is made possible through the utilization of a unique converter system that combines a multiport DC converter topology with a multilevel inverter topology, while maintaining a low component count and hence increased overall power density and efficiency for the proposed converter system. Unlike previous literature, where each energy source needs a separate DC converter and a two-level converter is used for DC to AC conversion, this converter system features buck-boost operation, superior power quality characteristics, and fewer components. The system suggests the implementation of a DC link voltage balancing technique that relies on an auxiliary circuit to achieve equilibrium in the voltage on the DC link, as a possible substitute to the more complicated control-based balancing scheme. The operational integrity of the converter system is assessed through rigorous numerical simulations and experimentally validated using OPAL-RT’s OP5700 hardware-in-the-loop (HIL) implementation platform as well as an in-house experimental test setup.