http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

The deep sea remains the largest unknown territory on Earth because it is so difficult to explore1–4. Owing to the extremely high pressure in the deep sea, rigid vessels5–7 and pressure-compensation systems8–10 are typically required to protect mechatronic systems. However, deep-sea creatures that lack bulky or heavy pressure-tolerant systems can thrive at extreme depths11–17. Here, inspired by the structure of a deep-sea snailfish15, we develop an untethered soft robot for deep-sea exploration, with onboard power, control and actuation protected from pressure by integrating electronics in a silicone matrix. This self-powered robot eliminates the requirement for any rigid vessel. To reduce shear stress at the interfaces between electronic components, we decentralize the electronics by increasing the distance between components or separating them from the printed circuit board. Careful design of the dielectric elastomer material used for the robot’s flapping fins allowed the robot to be actuated successfully in a field test in the Mariana Trench down to a depth of 10,900 metres and to swim freely in the South China Sea at a depth of 3,224 metres. We validate the pressure resilience of the electronic components and soft actuators through systematic experiments and theoretical analyses. Our work highlights the potential of designing soft, lightweight devices for use in extreme conditions. A free-swimming soft robot inspired by deep-sea creatures, with artificial muscle, power and control electronics spread across a polymer matrix, successfully adapts to high pressure and operates in the deep ocean.

Self-powered soft robot in the Mariana Trench

Hydrogen technologies can play an important role in decarbonising our energy system in a variety of ways across the energy value chain. It is therefore critical to identify the strategic roles as well as the conditions under which hydrogen energy systems become attractive for the energy transition. In this paper, the authors present a techno-economic review of hydrogen energy systems including power-to-power, power-to-gas, hydrogen refuelling and stationary fuel cells. We focus on their optimal operation as flexible assets and we identify three actions that can foster their uptake beyond technological progress. First, we recommend optimal electricity supply with dedicated control strategies considering that electricity dominates the levelised cost of hydrogen production via electrolysis. Secondly, hydrogen can enable the further integration of traditionally independent sectors, namely electricity, heat and transport while contributing to decarbonise all. This position can also be advantageous for investors who sell heat and fuels as energy efficient products. Lastly, we examine a whole range of revenues from different products and applications which can be combined (i.e. benefit stacking) to match capital and operational expenditures. We discuss these roles in depth and we conclude that policy makers together with technology developers should elaborate smart strategies to reduce cost by scaling production, stimulate standardisation (e.g., similar to the PV industry) as well as develop new market structures and regulatory frameworks which allow hydrogen technologies to deliver multiple low carbon applications and products.

A review on the role, cost and value of hydrogen energy systems for deep decarbonisation

Is microbial fuel cell technology ready? An economic answer towards industrial commercialization

This article reviews the design and evaluation of different DC-DC converter topologies for Battery Electric Vehicles (BEVs) and Plug-in Hybrid Electric Vehicles (PHEVs). The design and evaluation of these converter topologies are presented, analyzed and compared in terms of output power, component count, switching frequency, electromagnetic interference (EMI), losses, effectiveness, reliability and cost. This paper also evaluates the architecture, merits and demerits of converter topologies (AC-DC and DC-DC) for Fast Charging Stations (FCHARs). On the basis of this analysis, it has found that the Multidevice Interleaved DC-DC Bidirectional Converter (MDIBC) is the most suitable topology for high-power BEVs and PHEVs (> 10kW), thanks to its low input current ripples, low output voltage ripples, low electromagnetic interference, bidirectionality, high efficiency and high reliability. In contrast, for low-power electric vehicles (<10 kW), it is tough to recommend a single candidate that is the best in all possible aspects. However, the Sinusoidal Amplitude Converter, the Z-Source DC-DC converter and the boost DC-DC converter with resonant circuit are more suitable for low-power BEVs and PHEVs because of their soft switching, noise-free operation, low switching loss and high efficiency. Finally, this paper explores the opportunity of using wide band gap semiconductors (WBGSs) in DC-DC converters for BEVs, PHEVs and converters for FCHARs. Specifically, the future roadmap of research for WBGSs, modeling of emerging topologies and design techniques of the control system for BEV and PHEV powertrains are also presented in detail, which will certainly help researchers and solution engineers of automotive industries to select the suitable converter topology to achieve the growth of projected power density.

DC-DC Converter Topologies for Electric Vehicles, Plug-in Hybrid Electric Vehicles and Fast Charging Stations: State of the Art and Future Trends

https://orbit.dtu.dk/files/6490682/prod21326809149642.Technoport%202012_Power%20electronics%20converters%20for%20fuel%20cell%20hybrid%20system%20applications_final%20paper2%5B1%5D.pdf

A Review and Design of Power Electronics Converters for Fuel Cell Hybrid System Applications

Silicon Carbide (SiC) power devices can provide a significant improvement of power density and efficiency in power converters. The switching performances of SiC power devices are often a trade-off between the gate driver complexity and the desired performance; this is especially true for SiC BJTs and JFETs. The recent introduction of SiC MOSFET has proved that it is possible to have highly performing SiC devices with a minimum gate driver complexity; this made SiC power devices even more attractive despite their device cost. This paper presents an analysis based on experimental results of the switching losses of various commercially available Si and SiC power devices rated at 1200 V (Si IGBTs, SiC JFETs and SiC MOSFETs). The comparison evaluates the reduction of the switching losses which is achievable with the introduction of SiC power devices; this includes analysis and considerations on the gate driver complexity and cost.

Switching performance evaluation of commercial SiC power devices (SiC JFET and SiC MOSFET) in relation to the gate driver complexity

Energy production from renewable energy sources is continuously varying, for this reason energy storage is becoming more and more important as the percentage of green energy increases. Newly developed fuel cells can operate in reverse mode as electrolyzer cells; therefore, they are becoming an attractive technology for energy storage grid-tie applications. In this application dc-dc converter optimization is very challenging due to the large voltage range that the converter is expected to operate. Moreover, the fuel-electrolyzer cell side of the converter is characterized by low voltage and high current. Dc-dc converter efficiency plays a fundamental role in the overall system efficiency since processed energy is always flowing through the converter; for this reason, loss analysis and optimization are a key component of the converter design. The paper presents an isolated full bridge boost dc-dc converter (IFBBC) designed for this new application focusing on losses analysis. The system topology is briefly discussed and the major concerns related to the system, cells stacks and converter operating points are analyzed. The dc-dc converter losses are modeled and presented in detail; the analysis is validated on adc-dc converter prototype rated at 6 kW 30-80 V 0-80 A on the low voltage side and 700-800 V on the high voltage side (for a grid-tie application). The prototype is based on fully planar magnetic, Si MOSFETs, Si IGBTs and SiC diodes; efficiencies up to ~96.5% and ~97.8% were demonstrated depending on the converter operating point.

/pdf/isolated-full-bridge-boost-dc-dc-converter-designed-for-4zhwpib6lj.pdf

Isolated full bridge boost DC-DC converter designed for bidirectional operation of fuel cells/electrolyzer cells in grid-tie applications

Components for offshore wind farms are required to be highly reliable due to harsh environmental conditions and poor accessibility for maintenance Direct-Drive Permanent Magnet Synchronous Generator (PMSG) connected with back to back converters represents an attractive solution for large offshore Wind Energy Conversion Systems (WECSs) Large direct driven Wind Turbine Generators (WTGs) operate at lower speed compared to conventional geared WTs with operating frequencies that can be as low as 6–13 Hz (eg Enercon) The low operating frequencies introduce a continuous power cycling of the semiconductor devices and can lead to a reduced lifetime of the generator side converter Accurate thermal models integrated with circuital simulations can assist in predicting these stresses and in analyzing countermeasures This paper describes a method for thermal analysis of power converters based on a custom developed module in PSCAD/ETMDC that implements a thermal model running in parallel to the electrical simulations The custom module calculates the power dissipation and the temperature of the devices based on their physical characteristics and on their operating conditions derived from the electrical simulation The method is applied for the analysis of a Voltage Source Converter (VSC) connected to the PMSG in a Direct Drive WECS The simulations prove that the worst operating condition for the generator side converter in the sample system examined is represented by the turbine generating at its rated power The temperature swings over the power semiconductors at lower power and lower generator frequency induce a minor stress However, the worst operating condition may not correspond to the rated power in other cases especially for Direct Drive PMSG-WTs with a relatively low number of poles

Thermal stress analysis of IGBT modules in VSCs for PMSG in large offshore Wind Energy Conversion Systems

In this paper an analysis of two planar transformers designed for high-current switching applications is presented. Typical converter application is represented by fuel and electrolyser cell converters. The transformer designs are based on E+I and ER+I planar cores while the analysis focuses on winding resistance and leakage inductances which represent the main concerns related to low-voltage high-current applications. The PCB winding design has a one to one turn ratio with no interleaving between primary and secondary windings. The main goal was to determine if ER planar core could provide a significant advantage in terms of winding losses compared to planar E cores. Results from finite element analysis highlight that low frequency winding resistance is lower for the ER core since it is dominated by the lower mean turn length however, as the AC-resistance becomes dominating the winding eddy current losses increases more in the ER core than in the E core design. Calculated and simulated leakage inductances for the analyzed cores do not show relevant differences. A laboratory prototype based on E64 planar core is used as reference. Laboratory measurements highlight that FEM analysis provides more realistic results when computing the winding AC-resistance.

/pdf/analysis-of-planar-e-i-and-er-i-transformers-for-low-voltage-3k1rk442yf.pdf

Riccardo Pittini

Papers

A Review and Design of Power Electronics Converters for Fuel Cell Hybrid System Applications

Switching performance evaluation of commercial SiC power devices (SiC JFET and SiC MOSFET) in relation to the gate driver complexity

Isolated full bridge boost DC-DC converter designed for bidirectional operation of fuel cells/electrolyzer cells in grid-tie applications

Thermal stress analysis of IGBT modules in VSCs for PMSG in large offshore Wind Energy Conversion Systems

Analysis of planar E+I and ER+I transformers for low-voltage high-current DC/DC converters with focus on winding losses and leakage inductance