Dc‐link capacitor sizing is a critical aspect of inverter design. This study investigates capacitor sizing for three‐level neutral‐point‐clamped and cascaded H‐bridge inverters, based on an analysis of dc‐link capacitor current. Methods used to derive expressions for the root‐mean‐square (rms) value and harmonic spectrum of the capacitor current in two‐level inverters, are extended to the three‐level inverters. A new numerical approach is also proposed for calculating the capacitor rms current and voltage ripple. MATLAB code is given for the proposed approach, which can be easily adapted to different modulation strategies and applied to higher‐level inverters. Capacitor sizing parameters derived according to this approach are presented for a number of common modulation strategies and are used to compare the requirements of the examined three‐level topologies. Results are validated by simulations using MATLAB‐Simulink.

Global Maximum Power Point Tracking (GMPPT) algorithms can extract the maximum available power from photovoltaic (PV) arrays even under partial shading conditions. The existing GMPPT algorithms originate from computationally-intensive optimization (heuristic) or artificial intelligence concepts which operate in discrete time-steps and impose intense variations to the demanded PV array voltage/current. These result in undesirable disturbances which increase the overall time required for the GMPPT process to complete and affect the quality of power injected to the grid. In this paper, a new GMPPT method with low computational complexity is presented, which exploits the dynamic response of the PV system. The proposed GMPPT technique can track the GMPP in significantly less time when applied to PV inverters with high PV-side capacitances, guarantees convergence to the GMPP even under complex partial shading conditions, while also avoiding the aforementioned disturbances. The performance of the proposed GMPPT method is evaluated using an experimental setup incorporating a 2kW single-phase grid-tied transformerless PV inverter and a rooftop PV array. The experimental results show that it can identify the GMPP in approximately 1 s under various operating conditions, which is more than 95% faster than the P-V curve scanning and Particle Swarm Optimization GMPPT algorithms.

The maritime industry is a major source of greenhouse gas (GHG) emissions, largely due to ships running on fossil fuels. Transitioning to hydrogen-powered marine transportation in the Mediterranean Sea requires the development of a network of hydrogen refueling stations across the region to ensure a steady supply of green hydrogen. This paper explores the technoeconomic viability of harnessing wave energy from the Mediterranean Sea to produce green hydrogen for hydrogen-powered ships. Four promising island locations—near Sardegna, Galite, Western Crete, and Eastern Crete—were selected based on their favorable wave potential for green hydrogen production. A thorough analysis of the costs associated with wave power facilities and hydrogen production was conducted to accurately model economic viability. The techno-economic results suggest that, with anticipated cost reductions in wave energy converters, the levelized cost of hydrogen could decrease to as low as 3.6 €/kg, 4.3 €/kg, 5.5 €/kg, and 3.9 €/kg for Sardegna, Galite, Western Crete, and Eastern Crete, respectively. Furthermore, the study estimates that, in order for the hydrogen-fueled ships to compete effectively with their oil-fueled counterparts, the levelized cost of hydrogen must drop below 3.5 €/kg. Thus, despite the competitive costs, further measures are necessary to make hydrogen-fueled ships a viable alternative to conventional diesel-fueled ships.

This paper provides a methodology for deriving a family of output characteristics (DC-side I-V and P-V curves) for a passive magnetic energy harvester (MEH) clamped on a sinusoidal current-carrying conductor. It is demonstrated that MEH characteristics depend on primary current magnitude and frequency as well on load voltage. First, expressions for power harvested by a MEH are derived employing nonlinear B-H curve approximation of the core. Then, conversion losses are assessed to provide respective estimates for the power provided by the MEH to the load. Presented analytical findings are accurately supported by experimental results of MEH designed to harvest up to 240W from a conductor carrying currents of up to 350A.

A known issue with transformerless photovoltaic (PV) inverters is the generation of common-mode (CM) ground leakage currents. Single-phase transformerless topologies have been proposed that can achieve CM current suppression, but the relevant concepts do not perform equally well when applied to three-phase topologies. Existing three-phase transformerless topologies also have increased component count and losses, while their modified modulation strategies typically reduce output voltage quality and DC-bus voltage utilization. This paper presents a new three-phase PV inverter topology which achieves CM current suppression by incorporating a modification, the addition of a diode, in the boost converter that precedes the three-phase inverter stage. The boost converter switching is coordinated with that of the inverter, which operates based on an adapted modulation strategy that practically eliminates the CM current when the PV array voltage is lower than a certain threshold. For higher PV array voltages, conventional modulation strategies can be applied, which are also shown to reduce the generated CM current by up to 90%. All the above strategies retain a high output voltage/current quality, while the added diode losses have a minor impact of approximately 0.3% on the converter efficiency. The effectiveness of the topology with respect to CM current suppression is demonstrated through simulations in MATLAB/Simulink and experimental results from a comprehensive laboratory setup.